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Gerald_D
Mon 26 February 2007, 11:55
Here is a prelim. schematic for router users on 110V/220V split phase. Does it make sense? More importantly, does it look safe?

I know there are no fuses in there. We have circuit breakers on the incoming supply line.

(The wiring around the contactor was later proved to be faulty - see further in this thread jump (http://www.mechmate.com/forums/showthread.php?p=3394&postcount=55))

http://www.mechmate.com/Forum/messages/3347/3562.gif

This post will be edited often. The headings are placed here for notes.......

E-Stops on Gantry & Y-Car
WEG 22mm Non-metallic, Single Contact Block, 1 N.C. Price: $2.00 each (needs "operator" and enclosures with other "buttons" & switches)
Spec (http://factorymation.info/pushbuttons/WEG_PB_Specs.pdf) FactoryMation page (http://www.factorymation.com/s.nl/it.A/id.538/.f)



On / Off Pushbuttons
WEG 22mm Non-metallic, Double Pushbutton Operator w/ center illumination lens , IP40, "I / O", Price: $7.00 Requires Contact Blocks (http://www.factorymation.com/s.nl/sc.2/category.92/.f) (1ea BC10 and BC01 sold seperately) (Lamp block (http://www.factorymation.com/s.nl/sc.2/category.93/.f) optional)
Spec (http://factorymation.info/pushbuttons/WEG_PB_Specs.pdf) FactoryMation page (http://www.factorymation.com/s.nl/it.A/id.483/.f)



Disconnect
ENSTO Rotary Load Break Disconnect Switch, 3 Pole, 600V, 40A Price: $16.50 (needs handle & accesories)
Spec (http://factorymation.info/catalog0107/fmcat0107_27-28.pdf) FactoryMation page (http://www.factorymation.com/s.nl/it.A/id.4511/.f)



Contactor
TECO IEC Contactor - 16A, 120VAC / 60Hz Coil, 3 Pole 600V, 1 N.O. Aux Price: $12.00
Specs (http://factorymation.info/motor_controls/CN-9toCN-16.pdf) FactoryMation (http://www.factorymation.com/s.nl/it.A/id.90/.f)


Router Relay
Switched directly by 5V TTL from PMDX-122 breakout card. Do not connect relay "coil" or input to the mains circuit!
Magnecraft Solid State Relay, DIN Rail Mount with Heatsink, 25A SPST, Zero Cross NO, 280VAC max, 3-32VDC Coil, with LED, Price: $39.00
Spec (http://factorymation.info/relays/SSR-DIN.pdf) FactoryMation page (http://www.factorymation.com/s.nl/it.A/id.756/.f)

110V Toroid Transformer
For the recommended motors (1.5Amp max), a 300VA transformer with 50V AC output. link (http://www.mechmate.com/forums/showthread.php?t=50). About 125mm (5") outside diameter. Price about $70.
Mouser has a Hammond 182S24 which is 500VA 48V @ $96 - they don't seem to have 300VA at that voltage. Mouser Page (http://www.mouser.com/search/refine.aspx?Ntt=546-182S24%09) This will work with slight space & cost penalties - the heat will be the same, and bigger motors can be handled in future.


Rectifier
100V 25 Amp rectifier (total overkill, but no real size or price penalty) is being used because it has a metal case and pluggable connectors. International Rectifier 26MB20A D-34 package About $3 - $7 Mouser Page (http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016+688606+2445351&N=1323038+4294821599+2445351+0&GetRecs=1&Ns=P_SField&Msb=0&RefType=Header)


Capacitor/s
Cornell Dubilier DCMC103U100AD2B Computer Grade Electrolytic Capacitors 100 Volts 10000uF 1.375"Dx4.625"H Screw Terminals Price $25.34
Spec (http://www.cde.com/catalogs/DCMC.pdf) Mouser Page (http://www.mouser.com/search/refine.aspx?Ntt=598-DCMC100V103)


110V Cooling Fan
EBM-Pabst, AC Fan 92mm 115VAC 52.4CFM, Price $46.06
Spec (http://www.mouser.com/search/refine.aspx?Ntt=5912-3606) Mouser page (http://www.mouser.com/search/refine.aspx?Ntt=5912-3606)


110V/9V Transformer
A more friendly mounting system is needed, but this is the equivalent of what I used:
Transera/Pulse BV030-7305.0, Encapsulated Transformer 2 VA 9V@222mA Price $5.62
Spec (http://en.produkte.era-online.de/user/eesy.de/era-online.de/produkte/dwn/08_lt_ei30_15_5.pdf) Mouser Page (http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016&Ntt=*BV0307305.0*&Ntx=mode%2bmatchall&Mkw=BV030-7305.0&N=1323038&Ntk=Mouser_Wildcards)
The ncPod will probably eventually replace the PMDX-122 - it requires 5 vdc regulated at about 250 ma. The PMDX-122 can also live off 5V regulated 200mA now. Small DIN rail 5V supplies are expensive! $80 from Mouser (http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016+688729&N=1323038+4294797680+0&Ntt=*DIN*+*rail*+*power*+*supply*&Msb=0&Mkw=DIN+rail+power+supply)
Surface mounted 5V supplies are cheaper, but bigger. $37 Mouser page (http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016+688729+688552+182695 4+1826950+1525589&N=1323038+4294797680+4294944564+4294792938+4294792 672+1525589+0&GetRecs=1&Ntt=*power*+*supply*+*5V*&Msb=0&Mkw=power+supply+5V)


110V Router
The parts above assume the router draws no more than 15 Amps constant and 25 Amp on starts

Hugo Carradini
Tue 27 February 2007, 07:09
Gerald thanks for your time. This is a big help. No more guessing.

Mike Richards
Tue 27 February 2007, 08:08
Gerald,
I should have waited one more day before rewiring my test bench. Yesterday, I spent the better part of the day drawing up schematic after schematic as I tried different possibilities. What I ended up with is very similar to what you've posted.

The only practical difference is that I don't run the A.C. Neutral line through the contacts of any switch. It is hard wired all the way from the service panel to all parts of the control box.

My Alpha came from the factory with the neutral line running through switch contacts just like your design - so I don't know whether the way I wire is dictated by code or by convention.

The way that it was explained to me is that any line that is a voltage source is run through a switch and is fused at the service panel and, if necessary, in the circuits where it is used. That would mean that in North America where we split a single-phase 220/240 line into two 110/120 lines, both L1 and L2 would run through switches. If the circuit were three-phase, all lines L1, L2 and L3 would run though switches. But with a single-phase supply the neutral is not switched so that if a switch contact on L1 or L2 ever welded itself shut there would be no possibility that the neutral could be open so that the person operating the machine could become the path of least resistance in the electrical circuit.

Gerald_D
Tue 27 February 2007, 09:18
Not so fast Hugo, this stuff here is only for discussion. It could still be modified a lot. However, your comment "No more guessing" is exactly the reason why I ventured into this dangerous territory. It is better for me, and the rest of us, to learn about the correct way, instead of just guessing....

Mike, the breaking/disconnecting of the neutral line seems to have different approaches on the 2 sides of the Atlantic. Those "disconnects" from FactoryMation are only available as 3-pole over there - that tells me in 3-phase circuits the neutral is never disconnected. Same with motor contactors, practically all 3-pole.

Out here, (basically Euro standards), we break the Neutral at nearly every opportunity. For example, in domestic wiring, the supply to a cooker/stove must (mandatory) have 2-pole breaker which breaks the neutral as well as the live. In industry, a star-wired motor will have a 4-pole contactor. Feeds from main boards to sub-boards are isolated all lives plus neutal.

Our "ground fault" protection may be a bit different to yours.... If I work with a screwdriver inside an isolated sub-board or control panel, I can touch (short) neutral to ground/earth without problems because the neutral is disconnected. Were I to leave the neutral connected, touching it to ground/earth will plunge the whole building into darkness. We have one ground fault device where the feed enters the building. (this device must break neutral as well). If neutral touches ground/earth after this device it trips. You discover this when you put a knife into a switched off toaster to remove a crust.....
Do your ground fault devices only break "hot" (live) and leave the neutral connected as per your note above?

Where can we get some authoritive answers? In May I am taking an 220V electric motor to Atlanta. Guys out there are warned to stock up on candles...

Gerald_D
Tue 27 February 2007, 11:17
I find lots of references to "....shall have a single means for disconnecting all ungrounded main power supply conductors...."

Suppose the question now is whether the neutral is grounded or ungrounded. Before our ground fault protection device, the neutral is grounded. But after our ground fault protection device, the neutral is not grounded - I know this because accidental grounding of the neutral causes a fault trip.

Mike Richards
Tue 27 February 2007, 13:16
Gerald,
It's a can of worms (at least here in North America). I've just spent several hours on the Internet trying to find a definitive answer that would clear up the question once and for all time, but there doesn't seem to be that kind of answer. So, I went to a sub-panel that was installed by a licensed electrician to measure the resistance between earth ground and neutral. In the subpanel there was no resistance between the two wires. That matches MOST of the 'advice' on the Internet.

A ground fault interrupter (GFI) seems to be a special case. Here in North America they are required in bathrooms (and in kitchens if an outlet is near the sink). They do have an isolation between neutral and earth ground so that 'any' rise in voltage between earth ground and neutral will cause the GFI to activate and cut off or open the Line or Hot wire.

My 'impression', after reading the various opinions is that NOT switching the neutral wire is safer than switching the neutral wire IF and ONLY IF something out of the ordinary happened that caused the Line or Hot line to stay connected when the neutral line opened.

Sometimes I'm a lot more conservative in my opinions about AC wiring than others. In my past life as a process control computer designer, I've been severely shocked more than once when I've had to work on 'standard' wiring in film processors. Because of the alkaline nature of the developer and the acid nature of the bleach and fixer, there is often a lot of rust that eventually forms, even in switches. After a period of time, things start to fail and people like me are called in to sacrafice themselves for the good of society (at least it seems like that).

Personally, I've rewired my Alpha so that it is wired 'correctly'. Unfortunately, even with the door switch turned OFF, there is still lethal voltage inside the control box. The 240AC line that runs the spindle connects directly from the subpanel to a contactor inside the control box. The 120AC line that runs everything else also connects directly from the subpanel to a the door switch and then to a contactor inside the control box. (That's the way it should be.) If I were being prudent, anytime I opened the controller's door, I would first flip the breakers at the subpanel. But, being extremely wise, I put the subpanel where I can't get to it without crawling over the Shopbot. So, when I open the controller to check something, I place a strip of red electrical tape where ever there is 'live' power present. The tape won't protect me, but it acts as a flag to remind me to keep my fingers and screwdrivers away from those areas of the box.

I'm hoping that a licensed electrician will post something that gives some references from the code book that will authoritatively answer the question.

James Webster
Tue 27 February 2007, 14:41
Here in the USA the ground and neutral are run to the same bar in the breaker box.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/bregnd.html

Hugo Carradini
Tue 27 February 2007, 15:37
Gerald ¿What is the name of the terminal blocks that you show in the tread of correct wiring?
I don't handle correctly the technical names and there are so much different types in Mouser page that is frustrating.
Thanks

Mike Richards
Tue 27 February 2007, 16:09
James,
That's a good reference that's similar to many others that I browsed today. After a little searching on the link that you referenced, I found a page under AC circuits and then household wiring that shows the use of switches for L1 and L2 with Neutral being unswitched. (Sorry, but when I tried to copy the exact link to that page, it didn't work - instead it sent me to the home page.) However, even though I'm totally in agreement with it, I can't say for certain that it meets code. (And I have no reason to say that it doesn't meet code.)

James Webster
Tue 27 February 2007, 18:13
In the USA, if you are switching a 220v device (like a big hot tub), you disconnect both hot legs, leaving the neutral and ground connected.

They call this switch a "double pole".

Gerald_D
Tue 27 February 2007, 22:44
Very interesting discussion!

Here in South Africa, we also talk of having a "double pole" switch/isolator for critical equipment, but then it always means live and neutral. We don't ever have the 2-phase with 2 hots that you guys have.

Every mini-factory (built in the last 30years) that have seen here has a single ground fault protector adjacent to (or serving as) the main incoming breaker. Every single device inside that factory is then ground fault protected. We tend to treat Live and Neutral with equal respect. Look at the Euro "Schuko" plug on cords, they are not "polarity" protected.

Would your code prevent the Neutral from being broken like in my sketch above, or as ShopBot does their panels?

Gerald_D
Tue 27 February 2007, 22:51
Hugo, do you mean these (http://www.factorymation.com/s.nl/sc.2/category.79/.f)? From that company I would probably use the ER4 size (4mm wide). With Mouser, look near page 1263 - check current ratings, also don't go too small if you have big fingers.

Gerald_D
Tue 27 February 2007, 23:33
Mike & James, I can see your safety concern as a reason to keep the neutral connected, but what happens if someone "upstream" of you disconnects the neutral.....? Your disconnected portion of the neutral becomes hot if there is a load connected somewhere between you and the monkey that lifted the neutral.

James Webster
Wed 28 February 2007, 01:10
As crazy as this is going to sound, devices on 220v circuits tend to be the only device on a breaker. An electric stove, hot tub, whole house air conditioner, kiln, or tanning bed would never share the circuit with any other device.

Mini factories would step up to 3 phase service (usually not available to residential customers), this runs motors very efficiently. All three legs are hot, need overcurrent protection, and should be switched. 440v is popular, although 220v is also seen in 3 phase.

Mike Richards
Wed 28 February 2007, 04:11
This has become an interesting topic. Who would ever think that it would be almost impossible to find a definitive answer for such a simple question? Yesterday I spent a few minutes at the local library reading an outdated copy of The National Electrical Code handbook. The library had the 2002 edition. The 2005 edition, which is the latest edition, was not available. (A few minutes was not enough to find the answer. The index in that book is a total joke, as is the table of contents. Oh well, what should we expect from anything that has "National" as part of its title? Hopefully the book wasn't written by Republicans.)

I did find some interesting material on the APC website, particularly White Paper #21. (Edited: The link is not working properly, so you'll have to google APC White Papers, select White Papers from the APC support page, and then select White Paper #21 manually.) A copy also here (http://www.powermanagementdesignline.com/howto/51201145). Of particular interest to me was this paragraph:

"Electrical power flows in the form of current, which must pass through the equipment and then return to the
power source. Therefore, it is convenient to think of one wire to the load being the "source" wire and one
being the "return" wire. This simple model is appropriate for DC systems but does not work for an AC
system because the flow of the power is continually reversing direction with a frequency of 50 or 60 times
per second. From the point of view of the equipment or the power source, the source and return wires are
constantly being interchanged. In fact, no equipment can tell which wire is which! It is easily demonstrated
that the two power wires to any piece of AC equipment can be interchanged without any affect on function.
In fact, in Europe, unlike North America, the plug on a piece of equipment can be plugged in either way!"

As usual, I found something with which I disagree, which is the part that I marked in Red. It is my understanding that the "polarity" of the Line/Hot leads, i.e. L1, L2, L3 changes as the voltage level of each lead fluctuates along its sine way from zero volts to positive voltage to zero volts to negative voltage and then back to zero volts (where the amplitude of the positive and negative voltages depend on the type of service provided by the power company).

But, going back to the white paper, it seems that the reason that both the Line/Hot lead and the Neutral lead are switched in circuits using "European" type connections is because the "European" connection allows the leads to be reversed by rotating the plug in relation to its receptacle. On the other hand, in North America, with its polarized plug and receptacle, accidental reversing of Line and Neutral is not possible (although it can easily be done by buying a 99-cent "cheater" plug at any hardware store).

I "think" that since the Neutral lead and the Ground/Earth lead are connected in the power panel (again, I didn't find a reference that stated the code reference that required neutral and ground to be connected: I only found diagrams showing that type of connection), that switching or disconnecting the neutral wire via a switch would allow the Line/Hot lead(s) to use the Ground/Earth lead as a return path if the Line/Hot lead(s)'s contact did not open when the neutral contact opened. Since all exposed metal on a machine "should" be connected to Ground/Earth, any person touching the machine "could" be shocked with Line/Hot voltage.

(How's that for a long, convoluted answer? Sometimes I feel like I'm being a lawyer, or even worse, a politician.)

Gerald_D
Wed 28 February 2007, 05:10
What if the "MechMate Company" insisted that "their" control box be supplied from "15Amp circuit breakers with Ground Fault protection"?

(The organisers at the Atlanta show say little of their requirements in terms of electrical equipment. Once before I took equipment to a show in Munich Germany where they insisted on ground fault protection on my equipment, and that I must provide a 2-pin socket for them to plug in their tester. They allowed 30mA fault current - I passed at 20)

Mike Richards
Wed 28 February 2007, 07:19
Gerald,
Your Ground Fault question sparked an idea (no pun intended). I googled ground fault protection which led to OSHA which led to these OSHA Documents. (NOTE: The title for Part 1926 is "PART 1926 Safety and Health Regulations for Construction"):

1926.405(a)(2)(ii)(D)

Disconnecting switches or plug connectors shall be installed to permit the disconnection of all ungrounded conductors of each temporary circuit.

Then, I revisited the APC support site, re-read White Paper #21, particularly the part where "grounding" and "grounded" are defined:

"Ed" and "Ing"
In North America, much of the confusion regarding grounding has its roots in the National Electrical Code of
the United States. In the Code, the receptacle ground connection is referred to as the "Grounding"
conductor while the neutral connection is referred to as the "Grounded" conductor. The subtle difference
between "ing" and "ed" has led many to erroneously interchange these terms in the literature.

Further on in the OSHA document I found this:

1926.405(j)(4)(ii)(B)

The disconnecting means shall disconnect the motor and the controller from all ungrounded supply conductors and shall be so designed that no pole can be operated independently.

So, if we use the APC document that describes the neutral line as being "grounded", then, the neutral line is not required to be switched. However, if the neutral line is switched, then it must be switched with a multi-pole switch exactly as you drew in your schematic.

Reading further I found this reference about door switches:

1926.408(a)(3)(ii)

Guarding live parts. All energized switching and control parts shall be enclosed in effectively grounded metal cabinets or enclosures. Circuit breakers and protective equipment shall have the operating means projecting through the metal cabinet or enclosure so these units can be reset without locked doors being opened. Enclosures and metal cabinets shall be locked so that only authorized qualified persons have access and shall be marked with a sign warning of the presence of energized parts. Collector ring assemblies on revolving-type machines (shovels, draglines, etc.) shall be guarded.

I've marked in red the sentence which lists a requirement to have the electrical cabinet locked. Does that mean that screws are acceptable or must one use an actual keyed lock? Because this paragraph is related to portable equipment, perhaps the "locked" reference does not apply to "fixed" or "stationary" equipment.

Now, back to your question about GFI protection. I found this reference that seems to apply only to construction sites:

§1926.404 Wiring design and protection.

(b) Branch circuits-(1) Ground-fault protection-(i) General.

The employer shall use either ground-fault circuit interrupters as specified in paragraph (b)(l)(ii) of this section or an assured equipment grounding conductor program as specified in paragraph (b)(l)(iii) of this section to protect employees on construction sites. These requirements are in addition to any other requirements for equipment grounding conductors.

(ii) Ground-fault circuit interrupters. All 120-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites, which are not a part of the permanent wiring of the building or structure and which are in use by employees, shall have approved ground-fault circuit interrupters for personnel protection.

In my opinion - which counts for nothing - adding or requiring a GFI would give additional protection against electric shock and would be a very good idea.

After reading the OSHA documents (which may not even apply to an electrical enclosure used with a stationary piece of equipment), I'm inferring the following:

1. Because the neutral line is a "grounded" conductor, it is not required to be switched.

2. If the neutral conductor is switched, it must not be switched independently of the Line conductor(s) - i.e., a multi-pole switch must be used.

3. The neutral conductor may be switched unless other documentation is found that prohibits neutral conductor switching.

Gerald_D
Thu 01 March 2007, 06:11
Thanks for all the research and guarded opinions Mike. I think the really key point that you make is that; if you are providing switches to disconnect Lives/Hots and or Neutral, these switched must work simultaneously and in unison - ie. a single multi-pole switch.

My inclination towards disconnecting the Neutral as well, is probably because I can never be sure who has done what in the circuit before it reaches the box with my fingers inside. Remember we are a single-phase 220V country - Live & Neutral could be transposed in the box before ours and we would be none the wiser.

I havn't found a solid objection to disconnecting the Neutral together with the Lives/Hots, although I can understand the preference for a permanently continuous neutral in a well-managed and maintained system. I will stick with the above schematic for the time being.

Snag now is....where does one find 4-pole disconnects in the USA for 3-phase systems (for the spindle users)?

Mike Richards
Thu 01 March 2007, 11:08
On the AutomationDirect website (http://web4.automationdirect.com/adc/Shopping/Catalog/Circuit_Protection_-z-_Fuses_-z-_Disconnects/UL_508_Rated_Non-Fusible_Load_Disconnect_Switches/SD1_Series_Disconnects_(16-40_Amps)/SD1-025-BR), the spec. sheet for the SD-1 series of non-fused disconnects, shows an SD1-4P add-on module, which is described as an add-on 4th pole, rated at 40-amps.

There is neither a part number nor a price listing for that module. Perhaps you could email AutomationDirect to see if they carry that item.

Gerald_D
Thu 01 March 2007, 11:22
I know that Ensto makes the pole add-on module as well (because I use one here!), but FactoryMation doesn't seem to carry them "on-line".

AutomationDirect list their SD1 auxiliary poles here (http://web4.automationdirect.com/adc/Shopping/Catalog/Circuit_Protection_-z-_Fuses_-z-_Disconnects/UL_508_Rated_Non-Fusible_Load_Disconnect_Switches/Auxiliary_Contacts_-a-_Poles). There is a neutral pole module as well.

Mike Richards
Thu 01 March 2007, 13:02
I didn't look hard enough on the AutomationDirect web site. When I clicked on a 25A disconnect, the listing only showed the SD1-AUX module, which I knew was too small to carry its share of the load. I didn't think to search for the SD1-4P.

(I'm fortunate in only having 1-phase 240VAC power. Although it limits the size of equipment that I can run, everthing can be handled with 'standard' disconnects and contactors. The door disconnect for the electronics box that I'm beginning to design will only control a 1-phase 120VAC line. That 120V line will furnish power for the control circuitry inside the box, including coil voltage for the contactors through momentary normally closed pushbutton switches and manual over-ride switches. The main contactor will have emergency push-button switch(es) in series with its coil so that if an emergency switch is pressed, all contactors will turn off.

The contactor furnishing power to the toroid transformer that supplies the Geckos will have mechanical limit switches in series with its coil - and a manual over-ride switch - so that if a limit switch is tripped, power will be cut to the steppers. The manual over-ride switch will allow power to be restored so that the gantry can be jogged to a safe position. Proximity sensors will be completely separate from the limit switches. They will be used to determine an axis's home position and the limit switch will 'limit' the travel of an axis.

The contactor for the spindle or router will allow power to the spindle or router to be completely disconnected so that the cutters can be changed safely.

The auxiliary contactor(s) will be used to control dust collection, vacuum hold-down and possibly other auxiliary equipment.

Using contactors rather than manual switches will allow either manual switches or computer I/O to control the coils to the various contactors. Each contactor can be ordered with a coil suitable for its function and suitable to the device that controls it - switch or computer. The 30A contactors that are available at the local QED store seem to be excellent quality and only cost $30, including the extra side circuit, so, as long as everything fits inside a reasonably sized enclosure, I would rather have an electronics box that controls everything rather than running around the shop turning things on and off.)

Gerald_D
Thu 01 March 2007, 20:22
I am battling to come to grips with the terminology on your continent....when you say "I'm fortunate in only having 1-phase 240VAC power" don't you mean 2-phase or split-phase? It does have 2 Lives (Hots), doesn't it? Talking in the same way that we all talk of 3-phase when there are 3 Lives.

My approach with the circuit above is minimalist - mainly to reduce chance of interference inside the control box housing the tiny wiggly signals from the computer. I believe that the dust collector should have a local contactor and pushbuttons, and only get a control signal from the main box.

The router "safety disconnect" should be right at the router - too tempting to change a bit without walking to the control panel. (simple mechanical switch)

Mike Richards
Thu 01 March 2007, 21:43
Gerald, I agree that the term 1-phase makes no sense when referring to our 240VAC power. It is exactly as you describe: two Lines (L1 and L2), a Neutral and Ground/Earth, but that's the terminology that the power company uses. Your schematic at the beginning of this thread shows our '1-phase' power perfectly. L1 is a conductor with black insulation, L2 is a conductor with red insulation (or black insulation that is marked red with tape, shrink tubing or paint), Neutral is a conductor with white insulation and Ground/Earth is either bare (copper) wire or wire with green or green/yellow insulation. Personally, I think the name '1-phase' came from the fact that the '1-phase' 240VAC line is almost always split into two '1-phase' 120VAC lines inside the electrical panel in most homes and businesses. Only the 'big' appliances such as a clothes dryer, cooking stove or air conditioner would require both sides of the '1-phase' power line.

Sometimes I get carried away with my process control designs - not because going complicated is any better than a less complicated design, but simply because having a new challenge helps keep me interested in the project. All of us who have operated CNC routers for awhile know how frustrating electro-mechanical noise is. It literally wreaks havoc with control computers. When we slam contactors open and closed, with their contacts arcing and voltages spiking at many multiples of line voltage, as induction in some of the circuits causes voltage to pile up just as if it were a tidal wave rushing towards shore, the task of controlling everything can become daunting. But that's where the fun comes in. Adding snubber circuits, suppression circuits, and EFI filter circuits adds the spice that makes circuit design tasty.

The more practical reason for stuffing everything inside the box is that the sparking contacts can be placed in their own area, away from the control circuits. The weak I/O signals can be optically isolated from the high voltage circuits. That opto-isolation will also help to keep the small gauge I/O conductors from acting as antennas. (Edited: With opto-isolation, it's easy to use 12V or 24V I/O signals that can handle a lot more 'noise' than the 5V signals that are normally used.)

I'm still studying the router/spindle circuit disconnect. Handling a router disconnect is simple. All that is required is to add a mechanical switch into that part of the Hot side of the AC line that goes between the Solid State Relay and the router (for instance, the On/Off switch on the router itself). Then, even if some unanticipated event turns on the SSR, the mechanical switch will keep the power off.

A spindle is more complicated. The simple approach is to use a three-pole contactor and simply open the lines between the VFD and the spindle, but that could cause some expensive problems. At the very least, shutting the cooling fan off frequently while cutters are being changed could cause the temperature to rise too high. Cutting the power between the VFD and the spindle could also damage either or both devices. But, I prefer having a self-latching mechanical relay or contactor in the circuit that requires a button to be pushed to activate the circuit over a simple mechanical switch. (It's kind of like having a magnetic switch on the table saw. In the even of power failure, we want all equipment to stay off until we turn them back on. Having a table saw's blade suddenly start spinning just because someone at the power station restored power is not acceptable. Using a self-latching relay or contactor assures that power can only be turned on by a deliberate act on the part of the operator.)

But, the design has to be practical as well as safe. Your schematic at the top of this thread would handle almost any 'standard' design. It is robust, safe and elegant. There is nothing about it that needs changing. (I've even come to accept the fact that the Neutral line can be switched if it is switched by a multi-pole switch/relay/contactor.)

Gerald_D
Thu 01 March 2007, 22:19
My thinking is that a woodwork spindle, normally under the control of a computer, should have a mechanical disconnect switch for the guy changing the cutter, even if it may damage the VFD. An PE55 (http://www.factorymation.com/s.nl/it.A/id.4399/.f?category=)-like switch should be sitting directly above the cutter (say within 0.5m [2ft] and in view of the operator while the cutter is changed).
The only chance of this switch damaging the VFD is if the switch is turned off while the spindle is under load, which would be very unlikely. There is also a chance that the switch is turned on while the VFD is already on, but then you have probably saved a finger.
With a local mechanical switch, the guarded fan can stay running.

reza forushani
Sat 03 March 2007, 19:34
Can somebody explain the function of the contactor and how it works., I just got mine and need some help. thanks

Gerald_D
Sat 03 March 2007, 20:42
A contactor is simply a big relay. Does the sketch at the top of this thread help you at all? What relay did you get (photo or name&number)?

Mike Richards
Wed 07 March 2007, 10:31
This post was first made in this thread (http://www.mechmate.com/forums/showthread.php?t=58)

Here's a little circuit that shows James's circuit schematically as well as the reasoning behind using a bleeder resistor - even with stepper motors.


The schematic posted here previously has been deleted as per Mike's request lower down in this thread (Friday, March 09, 2007 - 02:28 am) This schematic (http://www.mechmate.com/Forum/messages/3347/3637.jpg) has replaced it.


In the middle of the schematic is the 70VDC power supply. The + side of the supply connects to the DIN rail terminal blocks through the 'A' contacts on the Contactor.

At the bottom of the schematic are the limit switches, 2 per axis. These are true limit switches in that they will remove power to the G202 modules if any one of them is opened. Notice the Limit Override Switch on the bottom right of the schematic. Its use is to temporarily 'override' a limit switch. It is turned on to supply power to the G202 modules, even if a limit switch is open. The purpose for the override circuit is to let the operator jog the axis that hit a limit switch back to the working area. The Limit Override Switch is a 2-pole switch. One pole bypasses the limit switches which allows power to be fed to the coil of the contactor. The other pole turns on a warning light (probably red) to warn the operator that the Limit Override Switch has been turned on. (Edited: When the Limit Switches are part of the Coil circuit, they only have to handle a small current, so they can be physically smaller than if they had to handle all of the power required by the controller.)

Just above the Limit Switches is the latching circuit that will turn on the Contactor. Two power supply lines, labeled Latch + and Latch - feed power to the coil of the Contactor. Depending on the voltage requirements of the Contactor's coil, the voltage might be 12VDC, 24VDC, 120VAC or 220VAC. Personally, I like to use the lowest possible voltage to avoid running high voltage through switches that are in close proximity to the metal frame of the machine - but that is just my personal preference.

In this particular latching circuit, when the Enable Push Button is pressed, the Contactor's coil is turned on. When the Contactor's coil is turned on, all of the contacts close, including the 'S' contacts. The 'S' contacts act as a bypass circuit that will furnish power to the coil when the Enable Push Button is released - which is why we call it a latching circuit. Once the coil is turned on, it will stay on until either a limit switch is opened or until the control circuit that furnishes the latching voltage is turned off. (As a side note, I always add a 'Stop' push button to every circuit that has an 'Enable' push button. The Stop push button, which would be a normally closed momentary switch, would function exactly as a 7th limit switch.)

After all of that background, we finally come to the purpose of having a Bleeder Resistor (R1) in the circuit. The whole purpose of having the limit switch/contactor circuit is to cut power immediately (20mS or less) when a limit switch is opened. No gradual power down is allowed - which could be the case with a large power supply and a single active motor. When the coil of the contactor looses power, all of the contacts are opened and all power to the G202 modules is cut off. With power cut off between the output side of the power supply and the G202 modules, the stepper motors cannot drain the power from the capacitors. (Remember, when power to the Contactor's coil is turned off, the G202 modules will be isolated from the power supply. That's a condition that will happen every time the controller is turned off.) However, with a bleeder resistor in the circuit, power will be drained from the capacitors. The time it takes to drain the capacitors depends on the resistance of the resistor. A low resistance will drain the capacitors more quickly than a high resistance. In this particular circuit, as Gerald suggested, a 22,000 ohm resistor would be a good compromise between too much heat and too slow bleeding; however, even though the math specifies 1/4-watt, I would use a 1-watt wire-wound resistor. A 1-watt resistor will still get hot, but not nearly as hot as a 1/4-watt resistor.

Gerald_D
Wed 07 March 2007, 11:05
Mike, I thought it was bad practice to diconnect a G202's power supply while the motor is moving? (the motor needs a place to dump its energy?) Have you seen anyone else put a contactor/relay between the gecko and its supply?

Mike Richards
Wed 07 March 2007, 11:51
Gerald, that's an interesting question and a question for which I don't have a definitive answer.

It is generally bad practice to manually turn a motor by hand (or manually move an axis) when the power if off, because, in that condition, the motor becomes a generator and generates power.

It is also a fact that a gantry will 'coast' to a stop, hopefully in a fraction of an inch, but that could represent hundreds or even thousands of steps.

I believe that the G202 is well protected against the voltage spike that shutting off the power would cause. The G203 is supposed to be 'unkillable'; so I believe that the G203 would not be damaged in any way.

On the yahoo groups Gecko forum, there is a paper that makes me think that nothing would be harmed. Here (http://f1.grp.yahoofs.com/v1/oP3uRQuk6BKNxK4JTpuE8ORsq6gsE17LDTWD-8SKbSFfnGVnrM9pP0Z5EYS04qX4uJIQq5C2GzPq5PI2tYoF8ds kqtB0NP_FOE0f9g/G202_G212%20Stuff/Scope%20Pics.pdf) is the link to that paper. (Non-members of that group may not be allowed to access the PDF file. I know that you're a member, but some readers of this post may not be.)

I will forward the schematic to Mariss and ask for his advice.

Gerald_D
Wed 07 March 2007, 12:37
My approach with E-stops is to use a pair of NC contacts under each E-stop button. One contact unlatches the main power contactor, cutting the input to the Gecko's supply...still leaving the issue of the capacitor being charged..

But, the second contact is wired to the PMDX-122 and its function is to stop the pulse stream instantly.

Mike Richards
Wed 07 March 2007, 20:36
Gerald, your approach with the E-stops is elegant. It would solve the problem as long as the sensor/switch/input latched itself like an E-stop does.

A properly designed limit switch should act that way. The ramp or cam or obstruction should continue to hold the N/C switch open until the condition has been corrected. My concern is that too many people don't realize that a switch that 'blips' OFF/ON/OFF or ON/OFF/ON momentarily, won't work without additional circuitry. That's the theory behind a latched relay or contactor. Anything that causes the coil to drop the contacts, will, by definition, keep the contacts from closing again until someone or something pushes a switch to re-latch the relay or contactor. It's relatively easy to design a micro-controller or logic circuit to act as a latch, but, I get the feeling that most CNC operators would rather not get involved with adding their own computer or logic circuitry to their controllers.

Running the power supply connections to the PMDX board through the contactor might be the best way to stop the steppers from stepping without damaging the circuitry. My philosophy about how a circuit should work often gets in the way of making the circuit practical.

My philosophy about emergency switches and limit switches is to cut the power from that particular circuit quickly and completely and to use fail-safe devices that prevent power from being restored until the operator manually turns the power back on. Probably overkill on my part. That philosophy dates back to my early years as a process control designer when I read horror stories about people being maimed or killed when someone defeated safety circuits. One particularly gruesome story told about a man who cut off an arm because someone had defeated one of the two switches that had to be pressed at-the-same-time for the cutter's blade to operate. Somehow, he had one hand and arm inside the machine pushing the material into position when he either pressed the other Operate button or somehow bumped the Operate button. Another man had both hands totally crushed in a 200-ton press when he personally rewired the machines two Operate buttons - that needed to be pressed at the same time - to a foot switch. He stepped on the foot switch when both hands were positioning some sheet metal. The owner of that shop was one of my best friends. Needless to say, he was overcome with grief when he realized that his employee had destroyed his own hands. He blamed himself for not personally checking the equipment for unauthorized modifications. His employee's reason for modifying the machine was very simple. He said, "I wanted to be a little bit more productive."

Every time I change a cutter in my Colombo spindle, the thought goes through my mind that the only thing that keeps that spindle from turning on is a 1.5 volt logic signal on a circuit surrounded by a very noisy 240V line and the latching contactor that is OFF and un-latched (thank goodness for that contactor). Some people don't realize that most TTL and computer circuits consider a voltage of 0 to 0.70 volts to be OFF and a voltage of 2.2 to 5 volts to be ON, so the difference between OFF and ON can be as little as 1.5 volts. That's really scary when you can watch on an oscilloscope voltage spikes on many of the TTL circuits that are many times that voltage.

Sometimes I think that designing safe, reliable, simple circuits that work in an industrial environment is impossible.

Gerald_D
Wed 07 March 2007, 22:27
Regarding mechanical latching of the cams/limits/e-stops, that is actually not essential. Once those NC switches have broken, they unlatch the main contactor (and Mach3). Re-making those switches will not close the contactor again, nor will Mach3 start without a reset at the keyboard.

The more I think about changing the cutters, the more I believe we have been amiss in not providing a disconnect switch right at the spindle/router. Whether our VFD is going to like it or not is a secondary issue.

Mike Richards
Thu 08 March 2007, 17:28
Gerald,
You and Mariss agree that cutting the power to the PMDX is the BEST way to stop a stepper. When I telephoned Gecko support a few minutes ago, Mariss answered the telephone, ran the math, and said that my idea of cutting the power between the power supply and the G202s would create an instantaneous current surge in excess of 400A per drive. In other words - disaster. On the other hand, cutting the power to the PMDX would cause no damage.

So, here's an updated schematic that shows the more proper way to stop the steppers when a Limit Switch is opened. This schematic will not allow the coil of the Contactor to be turned on unless ALL of the limit switches are closed OR the Limit Override Switch is turned on (which would also turn on the Warning Lamp as a visual indicator that the Limit Switches were no longer functional).

http://www.mechmate.com/Forum/messages/3347/3637.jpg

(NOTE: Gerald, if possible, please delete the posting of the other schematic or at least note that the schematic has been replaced with this schematic, so that there will be less confusion to those reading this thread.)

Gerald_D
Thu 08 March 2007, 22:48
Mike, your focus is "Limit Switches" while my focus is "E-Stops" - we are actually coming from two very different places. I personally don't regard limit switches as a personnel safety device (the mechanical stops prevent the gantry from landing on your toes) and my machines don't even have such switches.

The reason that I am mentioning this now, and possibly diverting this thread, is because Mach3 (together with PMDX) treat these switches differently to E-stops. These switches will stop motion "instantly", while Mach3 does not lose the calibration, and gives a facility to safely jog off the limit and carry on.

There is another facility in Mach3 to treat the same switches as "homing" switches for calibration - when in this mode, the operator does not have to do a "reset" when the switch is hit.

In short:
- while in normal cutting mode, the switches stop motion, the operator has to manually reset at the keyboard and jog away from the limit. The machine has not lost its calibration.
- while in homing/calibration mode, the switches act like our familiar z-zero plate, the machine does its little dance against the switch, backs off and waits. The machine is freshly calibrated.

The concept of limit/homing switches is well ingrained into the Mach3 software, literature, and videos. With respect, I think you are confusing the readers by coupling these as part of a power safety circuit.

Mike Richards
Thu 08 March 2007, 23:20
Gerald,
I agree that Mach 3 has provisions that make limit switches unnecessary. And, because my only experience with Mach 3 is on my test bench where I've never had a 'communications error' or a 'hiccup', maybe I'm just expecting unexplained errors to happen (like I've had with my Alpha). On more than one occasion, the Alpha has 'hiccuped', lost position, and then slammed into the stops before I could waddle over and hit the E-stop. Admittedly, these 'hiccups' are few and far between, but they have happened too often during the last (almost) three years. That is why I keep coming up with this particular type of circuit.

I also agree that when a limit switch is opened in the circuits that I've designed, that position will be lost and that the machine will have to go through a homing routine. For that, I prefer to use proximity switches that are totally separate from the limit switches. In my mind, the limit switch is the last resort to keep an axis from slamming into its stop, while a proximity switch could be placed at some convenient position to act as a homing switch. As long as the distance between the proximity switch and the true home position is know, offsets will take care of the rest.

Even though I prefer 'safety switches' for peace of mind, there's a Shopbot just across the street at the local High School where the students just plop down a piece of material, jog the axes to a corner of the material, give a Z2 command and start their cut. It's simple and effective and it doesn't require expensive and fragile circuits. The main difference between the High School shop and my shop is that at the High School, they don't allow the Shopbot to run unless a student is holding the E-stop in his hand to keep the unexpected from causing damage. In my shop, I nurse the machine the first few times a new design is run, but after those initial test runs, I do other work while the Shopbot does its work - and that's when the 'hiccups' happen.

Gerald_D
Thu 08 March 2007, 23:57
Don't get me wrong, I am not recommending that guys work without limit switches. The only thing that stops me from adding switches to my machines and to the drawings, is to find a commonly available, reliable, dust-proof system. (The drawings make provisons for 12mm proximity switches - but they can't be simply strung together in series) - this is a whole other thread by itself.

(The homing switch is a red herring here in this discussion because Mach allows the homing switch to be either the self-same switch as the limit switch, or the homing switch can be separate on its own input (movable or z-zero plate))

Gerald_D
Mon 12 March 2007, 22:51
When a USA-man-in-the-street buys a 220V appliance, takes it home, opens the box, finds that the power cord has 4 conductors (green, white, black, red) (maybe only 3, green/black/red?) without a plug at the end....what does he typically do? Is there a standard plug he can get from the hardware store? Are 220V plug outlets commonly fitted in the garage/basement/kitchen?

In case these sounds like stupid questions, over here all appliances for the man-in-the-street (except a stove) are 3 wire, plugs (from any store) are a DIY fit, and outlets are standard throughout a house or building. (Stoves are sold without a cord, and with a note: "to be installed by electrician....."

The main reason I ask about this is because I am dispatching a 220V motor to Atlanta tomorrow and I need to "plug it in" when I get there....

Mike Richards
Tue 13 March 2007, 07:32
The only 'standard' 220V-240V plugs that I've seen pre-installed are the receptacles for plugs (http://www.doityourself.com/invt/6410096) that are found on electric clothes dryers and electric cooking ranges.

There are many other configurations that are available. Most Home Depot sized stores carry a variety of plugs and receptacles. Here's (https://www.hubbellnet.com/max_htm/tech_stuff/NEMA/front.html) a link to a Hubbell reference chart. Many of the stores carry the Hubbell brand.

Gerald_D
Tue 13 March 2007, 10:39
The variety of pin configurations on that Hubbell chart had me gasping for air! And your Home Depot lets the DIY bloke loose among all these choices?....I am beginning to understand why fire-trucks feature in so many of your movies! http://www.mechmate.com/Forum/clipart/happy.gif

When ShopBot sells you a PRTAlpha for router duty, they imply that you have a DIY installation because they only insist on a licensed electrician for spindles. Does the average handyman really know how to handle those 4 wires?

Mike Richards
Tue 13 March 2007, 11:29
The chart makes everything look complicated, but it really isn't too bad. If we stay with two voltages 120V and 240V (although the chart says 125V and 250V), you'll note that the plugs/receptacles are sorted by their current rating and whether they are a standard plug/receptacle or a twistlock receptacle.

So, a 240V/20A receptacle can receive either a 15A plug or a 20A plug (which is how I've wired my planner, my dust collector and my air compressor).

A few minutes at the hardware store looking at the various plugs and receptacles takes most of the mystery out of everything.

Gerald_D
Tue 13 March 2007, 12:50
Okay, I have ordered a Hubbell HBL5666C (http://www.hubbellcatalog.com/wiring/section-a-datasheet.asp?FAM=Straight_Blade&PN=HBL5666C) plug for the 230V 11.5Amp Single Phase motor going to Atlanta. Let's hope the organisers can provide a suitable receptacle - I'll check with them tomorrow. Price of that plug out here: $25 - high because of rarity....

David Rosenbleeth
Wed 14 March 2007, 16:11
Gerald: Just ask the guys where you are planning to plug it in what amp receptacle, how many leads, and whether their receptacle is twist lock or not and then you can be sure to have the right one. Odds are a Home Depot is close to them (They are everywhere around Atlanta) and you could even make sure you have the right one by checking it out once you are there. The right amp plug will, of course, be determined by the circuit, not the motor. Most light industrial outlets here are 20 amp unless there is a dedicated reason to go higher. Of course the key word is "most".

By the way: I'm about a 10 Hour drive from Atlanta-Comne on down while you're here.

Gerald_D
Wed 14 March 2007, 22:54
10 hour drive - sure! http://www.mechmate.com/Forum/clipart/happy.gif

The plug I ordered here is the only "American" 230V plug that I could find stocked in South Africa. But at least I have a reference point to tell the exhibition organisers what I am bringing. They must have catered for stuff from Europe before, so I am not too worried about it.

Hugo Carradini
Wed 25 April 2007, 16:53
Hello Gerald and forum friends.
I moved to a new shop and that was a lot of work that keep me very busy for the last couple month.
Now I am ready to keep working on my project.
I got all my electronics except the cables (I will use normal cables for my "kitchen project" and the G203 "vampire drives that I hope arrive this week.
I all ready got the PK296A1ASG7.2 motors, Piltron transformer 300 VA 2x25 VAC 6amp, PMDX-135 Module, PMDX-122 card, ENSTO Rotary Load Break Disconnect Switch, 3 Pole, 600V, 40ª, and TECO IEC Contactor - 16A, 120VAC / 60Hz Coil, 3 Pole 600V, 1 N.O. Aux and the micelaneas in the list.
The question I have right now is how to install the contactor. I think many people is going to use the TECO IEC Contactor because is in the list you suggested and would be nice to know how to install it to the basic package. As soon I get my office strait out I will post the assemble process of the electronics so it can be cheeked out.
Thanks for your help.
Hugo Carradini
PD. My Web site is working now www.vitrales.com.ve (http://www.vitrales.com.ve)

Gerald_D
Thu 26 April 2007, 04:19
Welcome back! From the spec sheet:

http://www.mechmate.com/Forum/messages/3347/15105.gif http://www.mechmate.com/Forum/messages/3347/15106.gif

What is the supply voltage in your country? Single phase? Split phase? Three phase?

Normally 1, 3, 5 is used for incoming mains. 2,4,6 go out. Terminals A1 and A2 are lower down (normally under 13 and 14).

Hugo Carradini
Thu 26 April 2007, 09:13
Hello Gereald.
We work with 110 and 220 volts
110 uses a hot line and a neutral line and the 220 uses 2 hot lines and a neutral line.
I am planing in base of 110 volts system .

Gerald_D
Thu 26 April 2007, 09:32
So Hugo, you can follow the drawing right at the top of this thread. Here are your contactor connections:

http://www.mechmate.com/Forum/messages/3347/15109.gif

Mike Richards
Thu 26 April 2007, 13:10
Gerald,
After looking at your schematic, I think that pushing the N/O pushbutton is going to be an exercise in futility. If Contactor connector 3 is the connection for the incoming Neutral (as stated above), shouldn't the N/C pushbutton be connected between Contactor connector 3 and the Coil connection A1? That way, when the N/O pushbutton is closed, the coil will receive power from L1 and the coil will also have a complete circuit through the N/C switch to neutal. Also, when the N/O pushbutton is closed, switch terminals 13 and 14 will close and the Contactor will be self-latching. The Contactor will remain turned on until the N/C pushbutton is opened or until the disconnect/breaker feeding power to L1 is opened.

Gerald_D
Thu 26 April 2007, 13:36
Mike, after re-visiting the circuit, yes, you are right, pushing the NO will not do anything because the Neutral is broken.

But, I'll have to think harder about your suggested solution, because the neutral won't be isolated anymore - it will continue deeper into the circuit via the coil. I have a funny feeling that we are using a double-pole NO pushbutton to start the circuit? (Right now I am packing for 5 days away, 4 days back and then 10 days away again - need to chew on this one carefully....)

PS. I have purchased vBulletin software and will be converting this board so that the start of threads don't go so deep into the archives.

Gerald_D
Thu 26 April 2007, 13:37
As the first post shows (the faulty diagram):
http://www.mechmate.com/Forum/messages/3347/15112.gif

Mike Richards
Thu 26 April 2007, 14:46
Gerald,
You're right. A 2-pole, 1-throw N/O Pushbutton could be used to activate the relay. Once the Contactor's coil was activated, the coil would be held in the active state by switch contacts 13 and 14.

Good luck on your trip(s).

Hugo Carradini
Thu 26 April 2007, 17:08
Thanks Gerald.
I will be posting photos soon.

Gerald_D
Thu 26 April 2007, 22:06
Thanks Mike. Off to Oudtshoorn (http://images.google.com/images?sourceid=navclient&ie=UTF-8&rls=GGLD%2CGGLD:2005-07%2CGGLD:en&q=oudtshoorn) in an hour's time for a little break before the Atlanta visit.

Gerald_D
Tue 01 May 2007, 12:05
The long drive cleared the head. The Neutral going "permanently" to the coil of the contactor is no problem - there is a big multipole "disconnect" just to the left of the contactor. Follow Mike's "shouldn't the N/C pushbutton be connected between Contactor connector 3 and the Coil connection A1? That way, when the N/O pushbutton is closed, the coil will receive power from L1 and the coil will also have a complete circuit through the N/C switch to neutal. Also, when the N/O pushbutton is closed, switch terminals 13 and 14 will close and the Contactor will be self-latching. The Contactor will remain turned on until the N/C pushbutton is opened or until the disconnect/breaker feeding power to L1 is opened." until I can fix that drawing. Sorry for the slip.

Gerald_D
Wed 02 May 2007, 04:29
Mike, is this better?:

http://www.mechmate.com/Forum/messages/3347/15122.gif

Mike Richards
Wed 02 May 2007, 05:53
Gerald,
That looks good.

When the Disconnect is closed, Neutral is connected to the coil and L1 is available to the coil through the N/O switch. When the N/O switch is closed momentarily, the coil is energized and the contactor's auxiliary switch is closed, making the contactor self-latching. At that point L1, N, and L2 are passed through the contactor. When either the Disconnect or any of the N/C switches are opened, even momentarily, the coil loses power and the contactor opens all of it's switches.

Gerald_D
Wed 02 May 2007, 07:04
Thanks Mike. I still have to draw a "single phase" 230V version for "non-America" and that means the L2-L2-L2 rail at the bottom gets deleted. This is where somebody at some point upstream swops L1 and N around, and I was worried about the L1 getting deep into the circuit (via the coil) by mistake. We don't want a maintenance guy to find 230 V inside the circuit when it is OFF, but that is exactly what the Disconnect is there for.

Greg J
Thu 14 June 2007, 17:01
Thanks Mike. I still have to draw a "single phase" 230V version for "non-America" and that means the L2-L2-L2 rail at the bottom gets deleted. This is where somebody at some point upstream swops L1 and N around, and I was worried about the L1 getting deep into the circuit (via the coil) by mistake. We don't want a maintenance guy to find 230 V inside the circuit when it is OFF, but that is exactly what the Disconnect is there for.

Where does the BOB E-stop come into the picture from the one push button operator?

Greg

Mike Nash
Thu 14 June 2007, 20:39
Hi Gerald,

I do industrial controls for a living in the US. I just saw this thread and one thing that jumps off the page at me is the location of the Off/Estops vs the On Pushbutton. The ideal hookup would have L1 - Estops - Off - (On & Seal In Contact in parallel) - Coil - Neutral. The problem with the schematic below is that you can bypass/defeat the Estops simply by holding the On pushbutton in. Or if either the On or Seal In contact welded or if the operator switch broke you could not easily turn it off.

As far as I can see, you also have no need of the L2 line in the US anyway. The only benefit would be requiring it if the 110V router needed more than 20A since that is typically the max rating for a 110V outlet and wiring. The 220V lines can be run in 10 Gauge which is good for 30A per NEC.

Hey, I really admire what you are doing here!

Mike Nash




http://www.mechmate.com/Forum/messages/3347/15122.gif

Gerald D
Thu 14 June 2007, 23:45
Mike N, where have you been hiding while we needed you? Welcome!

You are dead right; the E-stops in the latest circuit can be defeated. Not good. Back to the drawing board....

The reasons I added the L2 are:
- Separates the noisy router from the control circuit (in 110V cases)
- Provides expansion/upgrade possibilities for folk wanting to add dust collectors or VFD's for spindles (also makes a progression to 3-phase easier - the right components are already in the box)
- 220 is a respectable voltage that I am more familiar with. :)

Gerald D
Fri 15 June 2007, 08:11
Hope I got it right this time. Still prefer a neutral travelling to all the moving parts and next to the low-voltage circuits, rather than a live(hot). I have a bad habit of fiddling on low-voltage circuits forgetting that mains might be nearby:

124

Have I got it right this time, Mike's N & R ? :o

Richards
Fri 15 June 2007, 09:07
Gerald,

It looks good to me. L1 latches the contactor on when the N/O pushbutton is momentarily closed. The coil to the contactor stays latched as long as the main disconnect (door switch) is closed AND the N/C switches (E-Stop, limit, etc.) stay closed. L2 becomes active when its switch is closed. The N/C switches are all shielded with a drain wire that connects on one end only to system/chassis/earth ground.

-Mike

Gerald D
Fri 15 June 2007, 10:39
Thanks Mike (R).

I am going to be bold and upload a few schematics before the other Mike gets here.

America's:
115V SINGLE PHASE SUPPLY Changed later - do not use this diagram
230V / 115V SPLIT-PHASE SUPPLY Changed later - do not use this diagram

Non-America's
230V SINGLE PHASE SUPPLY 127 Changed later - do not use this diagram
380V THREE-PHASE SUPPLY 128 Changed later - do not use this diagram

The missing one is the American 3-phase supply, because I don't know for sure what voltages you speak of there.

Please remember that the title of this thread has always been Mains power wiring for discussion. . . . .
- Mains power is the high voltage stuff that can kill you, and
- for discussion means that there could be mistakes, and that I would really appreciate everyone's input before it becomes the recommended way.

Marc Shlaes
Fri 15 June 2007, 10:47
Gerald,

Once these schematics mature and are critiqued by the experts, it might be a good idea to pull them all together and place them in the downloads area. I would keep your disclaimer on each page though. Just a thought.

Marc

Gerald D
Fri 15 June 2007, 10:57
Marc, they are intended for the downloads section eventually and have been numbered accordingly. There won't be a disclaimer on those drawings per se because everyone read the user agreement before registering to download, didn't they? ;)

Seriously though, there are a lot of things that can be dangerous when building this beast, and they are not all electrical. My blood ran cold the other day when I saw Kim's photo of a balanced steel beam with a tricycle next to it in his garage. Bandsawing and grinding are two other places of great concern.

Mike Nash
Fri 15 June 2007, 13:42
Hi Gerald,

The last was better, but at least in the US it is rare to see the neutral being switched and is possibly not to NEC code. It is also much, much easier to trace down open switches when you can put your meter between the wire and any available ground. I doctored your image in the venerable Paint program to show how I would wire it.

I included the fuse because I would prefer to pop a 1A (slo-blo) fuse if a wire shorted rather than blow holes in things waiting on a breaker to trip. Additionally, if the contactor coil shorted it lets out a lot less smoke as the shorts are rarely dead shorts, just partial winding shorts that create a lot of heat and smoke if not fused at a low enough value. Use a slo-blo type fuse due to inrush on the coil.

I also included an optional illuminated pushbutton (could be a separate lamp) to show that power was switched on. It can be helpful when trying to figure out why things won't start.

Keep up the good work!

Mike Nash

Gerald D
Fri 15 June 2007, 14:17
The fuse is a good idea, but what sort of package? (Solder to be avoided as far as possible).

Greg J
Fri 15 June 2007, 18:54
Mike,

I'm just trying to understand the circuit. When the on/off pushbutton is closed, don't you have a short on the switch above L1 and below the coil?

Greg

Mike Nash
Fri 15 June 2007, 20:09
Hi Greg,

The picture is a little unclear mostly because it is shown pictorially. I've put a standard E-Stop type circuit below with an added Off pushbutton. The C1 contact is the "seal in" contact that does indeed close around the On pushbutton to keep the contactor (relay) coil energized.

Mike,

I'm just trying to understand the circuit. When the on/off pushbutton is closed, don't you have a short on the switch above L1 and below the coil?

Greg

Greg J
Fri 15 June 2007, 20:26
Thanks Mike,

That helps, but I still don't get the seal in contact. Let me study it tonight and sleep on it. If it doesn't "click" in the morning, I'll ask another question.

Geeez, seal in contacts and short circuits .... you can guess what I'll dream about :)

Greg

Greg J
Fri 15 June 2007, 20:50
OK, I got it. Its a latching circuit. You are using a pushbutton and what keeps the circuits "closed" when the pushbotton is released (rhetorical question). The latching or seal in "leg" of the parellel part of the circuit completes the circuit. So I get my terminology correct, is it a "mini" relay?

Google "seal in" and contact and you come up with a great web site.
www.allaboutcircuits.com (http://www.allaboutcircuits.com)

Not too many better ways to spend a Friday night :D

Greg

Gerald D
Fri 15 June 2007, 21:31
Until yesterday I had never heard the term "seal in". And then you guys want to trust diagrams that I give you? :eek: :)

Thanks for the pro help Mike. The drawings will be revised. Yup, faultfinding a bunch of series switches on a Live circuit is a lot easier than on a Neutral circuit - I must stop forgetting that the "Disconnect" switch is there for when we want to work on ANY of the electrics/electronics.

A fuseholder terminal block (http://www.factorymation.com/s.nl/sc.2/category.14875/.f) is ideal for the fuse, but bad on the wallet. :( Oops they are priced on bulk batches of 20-50 pieces. Folk have mentioned that FactoryMation does sell smaller quantities.

These (http://www.automation4less.com/store/products.asp?cat=1136) look a LOT better on price! :) Singles

Greg J
Fri 15 June 2007, 22:12
A fuseholder terminal block (http://www.factorymation.com/s.nl/sc.2/category.14875/.f) is ideal for the fuse, but bad on the wallet. :( Oops they are priced on bulk batches of 20-50 pieces. Folk have mentioned that FactoryMation does sell smaller quantities.

These (http://www.automation4less.com/store/products.asp?cat=1136) look a LOT better on price! :) Singles

Gerald,

Better check the spec's a little closer. Dang, you just posted that one was bulk and the other was single. Your good.

I did notice, that the factormation "store" had better ratings (current/volts).

Greg

Gerald D
Fri 15 June 2007, 22:17
Greg, at the current or voltage level we are talking of here, the quality is not critical. Can buy purely on convenience/price.

Greg J
Fri 15 June 2007, 22:24
Agreed. But, for a newbie like myself, the factorymation site had better spec sheets.

Please don't ask what I'll do with the other 19 parts :)

Have a good evening. There is a good ball game on the "xm".

Greg

Gerald D
Fri 15 June 2007, 22:36
I think if you order FactoryMation by e-mail (not online) you can get smaller quantities.

(It is 6.36am here - the evening is long gone!)

Gerald D
Sat 16 June 2007, 07:12
Here we go again :) - extracted from this proposal: 133

132

May I use an "L" in the lamp?

Generally I don't like fuses. But in this case, I can't think of a more perfect application for a fuse. That loop going along all the E-Stops in series can be 20 meters [70 ft] long with about 10 joints, flexing as well, running tightly parallel to control signal cables, and exposed in about 3 control signal boxes - a tiny fuse is VERY cheap insurance!

Mike Nash
Sat 16 June 2007, 08:04
May I use an "L" in the lamp?



The L is fine. It simply seems to be a convention to use the first letter of the lens color inside the figure. A was for amber in this case, though any color is fine. The circuit looks great.

One possibilty for inexpensive fuse holders are those that mount in holes in panels and have a cap. Many of these can use crimp on connectors. But if you don't have the terminals and tool, then it gets pricey again. But as I have seen on your grounding thread, you really need the crimp tool anyway. The other issue with those holders is that they work best with a D shaped hole to keep them from rotating. Having said all of that, there are also holders designed for one fuse that can be soldered or use the crimp on terminals.

http://rocky.digikey.com/WebLib/Cooper-Bussmann/WEB%20DATA/HTB%20Panel%20Mount%20Series.pdf

http://www.newark.com/jsp/Electrical+&+Circuit+Protection/Fuse+Holders/LITTELFUSE/354601GY/displayProduct.jsp?sku=67K1780

http://www.newark.com/jsp/Electrical+&+Circuit+Protection/Fuse+Holders/LITTELFUSE/520003/displayProduct.jsp?sku=67K2290

Gerald D
Sat 16 June 2007, 08:45
Mike, I am very partial to DIN rail mounted components that are very common here and in Europe. I think this style (http://www.automation4less.com/store/products.asp?cat=1136) at at $2 - $3 is just right. (For these fuses one has to decide if they are going to be 20x5mm or 1x1/4")

While I have your attention, how fussy are you guys about the "flow direction"(?) inside a panel. For example, would you accept the bottom terminals of a contactor connected to mains and the top connected to the consumer - ie. flowing up? We tend to frown on that. We seem to want the consumer at the bottom and the supply from the top - ie. a disconnect switch will still be live(hot) on the top terminals even after turning off. Your comments?
(With bottom-entry cables it seems to make more sense to attach the mains to the bottom of the disconnect?)

Mike Nash
Sat 16 June 2007, 11:10
Yeah, I looked at your links after I posted mine. :o I like those fuseholders too as long as you have end clamps or other devices to support them, such as the relay/contactor. Plus you have to buy some DIN rail.

Bottom feed is something I run into. I got bitten by it Thursday as a matter of fact. I had voltage on the bottom of the fuses and none across the fuses so they must be fine, right? They weren't and I lost about 20 minutes futzing around with other possibilities before I discovered the fuses were fed from the bottom. It can be much more convenient at times, but I think they out to be labeled as such if it is done.

Gerald D
Sat 16 June 2007, 13:08
We used to mount the DIN (German Industry Standard) rails hard against the back panel, but then it was tricky to lay panel wires out the bottom of of one component and then to the top of the next component. Now we stand the DIN (Deutsche Industrie Norm) rail up on spacers so that we can pass the wires under the rail. Snag with this is that tracing the wires can lead to mistakes because they get hidden. (A dental mirror is useful for this tracing).

Here (http://www.mechmate.com/forums/showthread.php?p=2669&postcount=2) is a mix of top & bottom feed, even with the rail up on spacers. But I think that the flow is fairly logical. As you say, labelling and diagrams also help a lot. I just wanted your opinion if bottom feed might be against any codes?

Mike Nash
Sat 16 June 2007, 18:09
I just wanted your opinion if bottom feed might be against any codes?

I don't think it is against any codes in the US. The one I ran into was a US made, UL approved, digital DC drive package built by Reliance Electric.

Gerald D
Sat 16 June 2007, 20:43
Hopefully the last question on the bottom/top issue: Would any laugh if I fed this contactor (as an example) from the bottom on the T1 T2 T3 terminals? I reckon that turning the contactor over for upside-down markings is a worse crime to commit.

http://www.mechmate.com/Forum/messages/3347/15106.gif

Mike Nash
Sun 17 June 2007, 09:11
As far as bottom feeding a contactor, I'm not sure. The only example I found was another Reliance Electric design, but they had relabeled the terminals. I found this short discussion also but I don't have the NEC handbook.

http://forums.mikeholt.com/archive/index.php/t-62360.html

I also began to question the wisdom of switching the neutral. Again, there seems to be no definite rules against it I could find other than the mention below, and it may be referencing switching only the neutral. I don't remember it being something that is typically done in the US since the neutral is bonded to ground.

http://www.isa.org/Template.cfm?Section=Letters1&template=/ContentManagement/ContentDisplay.cfm&ContentID=40708

Gerald D
Sun 17 June 2007, 10:18
On bottom feeding, thanks for finding that discussion, and let's just avoid it altogether. (I plan to make more graphical drawings of the components on the DIN rail and you have helped me tremendously with real industry feedback)

Switching of the neutral is something that Mike R also had big problems with, but he eventually relented when it was made clear that we only switch the neutral simultaneously with the Lives (Hots) on a single multipole switch or contactor. We never think of the Neutral as something that is connected to Ground (Earth). In fact, because we have lots of Ground Fault Protection, touching Neutral to Ground (Earth) causes a trip (fault). Look at all continental Europe 2-pin plugs for 230V - they can be inserted any way around.

Snag is, we sometimes find that an idiot swops Neutral & Hot (Live) in a distribution board upstream and we are never 100% sure which of the two wires is 230V above ground potential. Maybe something similar to the US 230V single-phase where BOTH wires are treated with equal respect.

Bottom line is that we prefer switching both wires, but only in a switch that forces them to be switched simultaneously. However, since I am going to end up producing circuits for the America's versus the non-America's, I can avoid neutral switching in the one case.

Gerald D
Sun 17 June 2007, 11:22
Mike N, the simultaneous disconnecting of all Lives(Hots) and Neutral is equivalent to pulling the plug - what could be safer than that? :)

Mike Nash
Sun 17 June 2007, 15:40
Mike N, the simultaneous disconnecting of all Lives(Hots) and Neutral is equivalent to pulling the plug - what could be safer than that? :)

Well, yes and no. One of the issues with E-Stops in general is all of the new safety regulations that go with them. Depending on the assessed level of hazard to life and limb, it can get very pricey to properly construct an E-Stop circuit. This is true in the US as well as Europe. Worst case involves redundant contactors, safety relays (very pricey), and two pole force guided E-Stop pushbuttons.

The problem with breaking the neutral is that you don't know that it or the hot, really did break. Welded contacts are a fact of life. If you are holding a plug in your hand you can visually (or tactiley if you are vision impaired) tell that that all circuits are indeed disconnected.

Gerald D
Mon 18 June 2007, 09:29
. . . . Worst case involves redundant contactors, safety relays (very pricey), and two pole force guided E-Stop pushbuttons.

The problem with breaking the neutral is that you don't know that it or the hot, really did break. Welded contacts are a fact of life. If you are holding a plug in your hand you can visually (or tactiley if you are vision impaired) tell that that all circuits are indeed disconnected.

Mike, to the best of my knowledge, the Ensto multipole disconnect switches that I am promoting here, embody the principles of "safety relays" and "two-pole force guided E-Stop pushbuttons". These Ensto's are force-break or positive action switches - a single welded contact prevents the handle from turning and prevents any other pole from opening.

Mike Nash
Mon 18 June 2007, 11:04
Mike, to the best of my knowledge, the Ensto multipole disconnect switches that I am promoting here, embody the principles of "safety relays" and "two-pole force guided E-Stop pushbuttons". These Ensto's are force-break or positive action switches - a single welded contact prevents the handle from turning and prevents any other pole from opening.

That's good. And I was actually addressing the contactor as opposed to the disconnect switch. It's the reason redundant contactors are required in the applications that are considered to be more hazardous. I attended a three day "school" on safety devices and their use and application. All through the training it was repeatedly stressed that we were not to determine the hazards involved or suggest devices needed. The end user or equipment manufacturer was required to do that or they could contract a qualified (abundantly insured I'm sure) safety engineering firm to make the assessment as to what was required. My only intent is point out possible issues based on my expereince with equipment failures over the years.

Gerald D
Mon 18 June 2007, 11:49
Mike your words have been very much appreciated. The readers keeping an eye on this thread must have noticed:

- how tricky this subject can get and some of the risks to be considered,

- that it is not a simple DIY project to be tackled lightly

- how unqualified I am to be the guide in this area

Gerald D
Mon 18 June 2007, 12:52
Mike, how common is Ground Fault Protection over there? Would if be reasonable to specify that a MechMate can only be connected to a fused outlet with GFI? Out here that would be the de facto situation.

Mike Nash
Mon 18 June 2007, 15:37
Mike, how common is Ground Fault Protection over there? Would if be reasonable to specify that a MechMate can only be connected to a fused outlet with GFI? Out here that would be the de facto situation.

On a factory floor, it isn't common at all. Per NEC code, it is required in newly built or (re)wired home garages, kitchens, baths and outdoor receptacles. But most older garages don't have GFI and they are basically "grandfathered in" since they've already been inspected. I believe a dedicated, hardwired device in a garage, such as an air compressor may be exempt from the GFI requirement, but I won't swear to it. The NEC code is open to interpretation by the building inspectors and different municipalities may use different editions as their code book. It's a real mess really.

As far as requiring GFI protection, it would certainly be a good idea. Considering the wiring is being done mostly by nonprofessionals and that wiring is in motion, it would be a small price to pay to avoid the potential shock hazard. Despite the best grounding efforts it would still be possible to have exposed wiring a person could come in contact with, without it necessarily grounding out.

Gerald D
Wed 20 June 2007, 11:02
Installing a GFCI (http://www.cornerhardware.com/howto/ht067.html) : an article found on the web.

(Ground Fault Circuit Interrupt)

bphilpott
Tue 26 June 2007, 21:56
I would like to offer this as a possible main power/E-Stop schematic. I am know the symbols are not standard, but I think you can get the idea. What we have is the a relay similar to what you have spec'd earlier except with a 24V control, and next to that is a 24V transformer. When the on button is press, the relay will transformer will turn on, energizing the relay, witch will then continue to feed the transformer after you have releaced the button. The benefits to this setup are, the power will remain off after a power outage, less high voltage wireing running through all the moving parts, and it also gives you a good source of power for iluminated switches.

Gerald D
Sat 07 July 2007, 08:36
Brian, 24V control is common in industrial electronics, but I am loathe to introduce yet another voltage into the control box - we have enough confusion in there already. The other benefits you mention are already present:

"The benefits to this setup are, the power will remain off after a power outage, less high voltage wireing running through all the moving parts, and it also gives you a good source of power for iluminated switches."

Our latching circuit also stays off after a power outage and illuminated switches for 115V/230V are also easily available.