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  #1  
Old Sun 26 February 2012, 10:11
Mrich0908
Just call me: Mark
 
Bridgeport ct
United States of America
Power Supply for DC Brushless motor

I love this site its great ,
Im really happy I found it.
So I need a power supply to run a brushless motor for my spindle on my mill .
it has to be 80a 24v @1850watts +or- few volts .
Ive never built my own power supply . I was going to buy 2 high end computer PSU's and run them in series but I would not get the amps needed .
Then I came across this site and im hoping some one may lead me in the direction to maybe achieve a better result.
Thanks for any input.
Mark
  #2  
Old Sun 26 February 2012, 14:18
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Building an 80A 24VDC unregulated power supply takes a huge transformer, a huge bridge rectifier and a bank of capacitors.

A 17VAC transformer will give you about 24VDC (+/- a few volts).

You'll need about 275,000uF capacitance. That's 10X or more capacitance than most of us need for our stepper supplies. You will have to deal with inrush current. With that much capacitance, every time you turn on the power supply, the circuit will act like a dead short until the capacitors start to charge.

I would HIGHLY recommend that you talk to a specialist before even thinking about starting a do-it-yourself project.
  #3  
Old Sun 26 February 2012, 14:53
Mrich0908
Just call me: Mark
 
Bridgeport ct
United States of America
Mike,
Im not sure what power supply I should go with . Im not were to start what to look for . Im clue less this is step one for me.
The best solution ive come up with my problem thats cost efficient was 4 PC PSUs 2 pairs in parallel then taking those two pairs and running them in series ( im not sure if that can be done) but thats were i am.
Your suggestion of talking to a specialist is great but thats why I came here I was hoping to find a few.
If you were me what would you do? If need be I can under power / volt the motor this doesn't have to be exact.
Also this isnt to stepper motors.
  #4  
Old Sun 26 February 2012, 17:57
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
80Amp? your motor has AWG2 or 6.5mm thick wire? thats not very common

only things readily available at that amps are 24V 100amp battery chargers for truck and tractor batteries.
  #5  
Old Sun 26 February 2012, 23:57
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
The spindle that I used was a 3hp Colombo unit that used a Delta VFD controller. The spindle motor that you wrote about is not a motor that I have seen used on this type of CNC machine. That's why I suggested that you talk to an expert.

I am really afraid that you might hurt yourself or cause a fire if you try doing things the way that you've outlined. It is always best to completely understand how things work or to hire someone who does before designing your own solution.

This forum has a lot of people who have done a lot of things, but your post is the first time that I have read about anyone wanting to use an 80A 24VDC brushless spindle on a MechMate.
  #6  
Old Mon 27 February 2012, 02:41
KenC
Just call me: Ken
 
Klang
Malaysia
80A 24V... looks like a small arc welder specifications
  #7  
Old Mon 27 February 2012, 08:20
Mrich0908
Just call me: Mark
 
Bridgeport ct
United States of America
Maybe If I give you a better look at what im building you can further help me develop what I need.
Again The specs I gave you are for max power consumption on my motor .
here are some links. For spindle design . Post six shows ruffly what im thinking.
http://www.mycncuk.com/forums/showth...spindle-design
This will tie it in with Mach3. Scroll it in and you will see another design .
http://www.logicnc.com/rcnc.html
This is the motor im using, It runs ruffly 6850 rpm @24v
http://www.ebay.com/itm/SK5065-KV380...item4ab46f8680

I have a treadmill motor now im using as a spindle motor. It is great . Im just allbout further bettering things and love this idea.



Last edited by Mrich0908; Mon 27 February 2012 at 08:24..
  #8  
Old Mon 27 February 2012, 08:35
KenC
Just call me: Ken
 
Klang
Malaysia
Why not just convert a battered Bridgeport to CNC? Not only it is Cheaper, larger & better. you get to have a blast at rebuilding the Bridgeport. & you don't have to "develope" anything...
  #9  
Old Mon 27 February 2012, 08:39
Mrich0908
Just call me: Mark
 
Bridgeport ct
United States of America
Because I dont want to.?
This is not the only mill I own its just the project at hand.
  #10  
Old Mon 27 February 2012, 08:42
KenC
Just call me: Ken
 
Klang
Malaysia

I bet you will have a blast at playing with the power supply
Have fun!!!
  #11  
Old Mon 27 February 2012, 19:15
Mrich0908
Just call me: Mark
 
Bridgeport ct
United States of America
You sound almost upset i didn't take your suggestion on converting a Bridgeport?
Like o hold on some guy on the internet I never met says ............
Then make a cheesy joke my grandfather would make bout me hurting my self .
The only thing that can go with that comment is...
http://www.youtube.com/watch?v=X_mK0nrrsbI
  #12  
Old Mon 27 February 2012, 19:22
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
I think he meant that it really looks silly using a toy 400grams RC plane motor (which could not be rated for continuous duty) on a milling machine.
A PCB drill , some some hobby machine maybe, but we were really looking forward to see the monster motor of 80Amps and give some constructive advice how to use that on a industrial size cnc router, that Mechmate forum is all about.
  #13  
Old Mon 27 February 2012, 22:01
KenC
Just call me: Ken
 
Klang
Malaysia
Danilo read my mind.

Yes, I'm sort of disappointed when you don't want to convert a Bridgeport. If you would that will make 2 of us going that way.

Some day..... I will convert a milling machine... Some.....day........
  #14  
Old Mon 27 February 2012, 22:58
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
It looks like a foolish project to gear up a heavy spindle motor to do much less than a "normal" spindle would do.

We don't have to re-invent the wheel just because we have a log laying around. There are enough posts about regular spindles on this forum to lay to rest any idea that an 80A 24VDC brushless spindle is better.

Normally, I don't write posts like this, but this time, it just seems wrong to encourage someone to do something that doesn't need to be done.

A CNC router can't move that much mass as quickly as required to do the job that a CNC router is required to do. It's that simple. An 80A 24VDC brushless spindle is the wrong tool for the job.
  #15  
Old Mon 27 February 2012, 23:15
Mrich0908
Just call me: Mark
 
Bridgeport ct
United States of America
See , you just really dont know . These motors are the future. Would you believe it puts out 3.5 - 4 hp .
Probally not , it does. I bought a cheap one they run 4-500$ in the size I have.
Do some reading , look on you tube those relic motors your thinking are a thing of the past.
Theese are the motrs they use to power electric conversion cars now , They are the very same top notch company's like Grizzly , LMS ect ect use.
The numbers they give are rated for "continuous duty"
Im not a young man who does foolish things with his money for the hell of it. I read research and explore. Im into trying new things.
You should be willing to do the same you might be surprised.
I feel As if i came here and got shot down because im not doing something they approve of , a project of there liking. And I have to defend my right to do what I want with a project and idea im exploring . Becasue my motor isnt up to there , your standards.Allot of ignorance.
Expand your mind be wiling to try new things this is one idea were im sure you will be happy people have been using these motor on there mills for 16hrs a day with great success.
I just want some help finding the proper power supply for what I asked for. Thats all not a lecture and lesson on what you think is best for me. Thats up for me to find. out.
  #16  
Old Mon 27 February 2012, 23:18
KenC
Just call me: Ken
 
Klang
Malaysia
We might be crazy in the eye of the general public, but we do crazy thing with sound engineering fundamental...

If you must find a place to use that treadmill mot0r, how about using it as the starter motor for your car or better still build a electrical golf cart around it A connect a bank of 24volt battery in parallel & you don't have to build a welding machine to run it as a spindle.

BTW, We run our spindle at 24000rpm, 12000rpm is the minimum. that treadmill motor just doesn't make the cut.... not even close...

Last edited by KenC; Mon 27 February 2012 at 23:27..
  #17  
Old Mon 27 February 2012, 23:51
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by Mrich0908 View Post
......
I feel As if i came here and got shot down because im not doing something they approve of , a project of there liking.....
Right at the top of the front page of this forum it says: "This forum is exclusively for MechMate builders or people seriously interested in building them."

So yeah, you don't belong in this forum.

Quote:
Originally Posted by Mrich0908 View Post
And I have to defend my right to do what I want with a project and idea im exploring . Becasue my motor isnt up to there , your standards.Allot of ignorance. .....
You have no rights here. You are actually spamming this forum with stuff that doesn't belong here.
  #18  
Old Tue 28 February 2012, 06:41
Mrich0908
Just call me: Mark
 
Bridgeport ct
United States of America
How did I spam any one? I didnt show my plans or details until asked?
Theres allot of hostilities here .
I was hoping some one would help me with building a power supply.
Im on many other forums and help any one when I get the chance and thats what I think forums are bout.
Im trying to build a product I can build and resell. I know plenty off you dont agree that that may be the proper application for the motor . But there is a market none the less for it.
I just could really use some help and if the problem was in reverse I would help any one of you hands down and not give you a hard time about what you choose to do with you money and time.
Thank ,
Mark
  #19  
Old Tue 28 February 2012, 07:19
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Mark
The MM forum is designed to support the fabrication, use and implementation of a CNC machine called the MechMate.
The "hostilities" you may interpret are because your needs don't fit the realm of the MM. I typically don't chime in on the fodder - but Gerald, Mike Richards and others are really engineers. They have more knowledge in the fabrication, control and design of CNC equipment than most of the DIY folks here.

The advice you seek is better found at the CNC zone - or library.

This is not a rude reply, just a reminder that the sole focus of this forum is for MM and not "other projects".

Best of luck with your idea.

Sean
  #20  
Old Tue 28 February 2012, 07:31
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Unless this thread is heading towards actual use of a technology on a MechMate, then it is by definition off topic - it should be at a more general site like CNC Zone.

Unfortunately, Mark, the original question was tempting enough that it pulled in several of us before anyone observed this. Also, we're clearing talking across language barriers in some cases, and we have a long history of being patient in those situations.

It is true that BLDC technology is making some inroads in the hobby mill industry; small mills have long used DC motors for their simple controllers and good low speed torque, and moving to BLDC motors in the 500 watt category, 2000 RPM type of category makes some sense. Those motors often run hot, however, because the
manufacturers don't intend them for continuous operation.

Repurposing an open frame motor that is clearly not intended to run continuously at its peak output(*) is somewhat interesting, but even if you overcome the power problem, you still have to cope with the heat, the small shaft size, the slow speed (2,000 RPM != 20,000 RPM), and bearings designed for an easier job.

(*) if it were, you wouldn't see "120A" controllers with #12 and #14 wires on them.

So, while I agree that BLDC technology is cool, has a lot of activity and a lot of growth room - and I'm watching it avidly) - at the end of the day IT HAS NOTHING TO DO WITH A MECHMATE. And that is why we are politely (or less politely) suggesting that you take this conversation elsewhere, where it can be welcomed. While it might be a stretch to label a single off-topic post as spam, if it is repeated in the attempt to gain value from somebody for free, it becomes spam. And if it is interspersed with attacks on people, it's trolling too.

Long time users of this forum have gotten used to this pattern - somebody notices that there is good engineering talent here, walks in with an off topic or preposterous idea because they want access to that talent, gets a response they don't like from that talent, and then becomes upset and complains about the same people they were soliciting information from. I (not "us", I) think that's rude - ruder even that the responses generally given. Mark, you appear to be smarter than this, So I hope you decide to step back, go explore this technology at cnczone or elsewhere, and if you successfully come up with something that will drive a 1/2" mill through 3/4" plywood at 200 IPM then by all means come back and tell us you told us so. That would be on topic, and generally impressive to us.
  #21  
Old Tue 28 February 2012, 08:30
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by Mrich0908 View Post
......Im on many other forums and help any one when I get the chance and thats what I think forums are bout.......
I am going to sound blunt again, but you have an incorrect expectation of a forum. You cannot assume all forums are the same. Some forums thrive on max number of users, posts and pages....so that they can earn exposure and revenue via the advertisements around those forums. Notice the lack of advertisements; that already says that something is different here.

If the narrow interest of this forum is going to get diluted/spammed with off-topic threads like this, it might as well open the gates and have a free for all like CNCzone and I will stop looking in. Yes, it is selfish of me, but I do have a choice of what forum I would like to follow and I do have a right to state my opinion on this.
  #22  
Old Tue 28 February 2012, 09:22
Mrich0908
Just call me: Mark
 
Bridgeport ct
United States of America
Gerald,
I understand were your coming from and that is your right .
I just dont understand why it should matter to one user or another what I need a power supply for .
It may not be the correct application or the best use of my mill, motor or what not . The project of mine might be worthless and usless to allot of people, why that would matter. I would love a Knee mill I cant have one were I live at the moment.
If I cant help some one I dont thrash there thread complain about what there doing or make uncalled wise crack about them hurting them self's.
I simple just do not respond.
Allot of forums it seems as theres pissing matches . Some one new comes along , asks something from left field . Maybe it is unorthodox in the forum and unheard of but why is this of such importance to any one else to the point of rudeness. Then that member will bash the new member and like a pack a wolves every one jumps in. Its really uncalled for . Were all grown men here ... I think.....
I just wanted some help building a power supply. If you came to one of the many many forums I was at I really truly would help any one of you to the best of my ability . I have and will continue to .
If any one would be kind enough to point me in the correct way were I can read some literature that may help me solve my problem I would be grateful .


Brad,
Thank you and I am a member at CNCzone . I was looking for a forum I came across this one and seen some members here have knowledge in building power supply's.
I agree with everything you said . But untill you test and start using these motors technologie cant advance.
Im sorry for causing an disturbance in the forum.

Ken You really need to re read this thread.
The spindle people are building are hitting 40,000 rpm. Im dropping the tread mill motor for the new spindle. I think you may be a bit confused.
Im not looking to hit that rpm band but plenty are.

Last edited by Mrich0908; Tue 28 February 2012 at 09:34..
  #23  
Old Tue 28 February 2012, 09:38
KenC
Just call me: Ken
 
Klang
Malaysia
Mark,
Honestly, asking you to drop the idea is the best advise I can think of.
the 2nd best advise is to use a welding set to power your motor.
the 3rd best is to use a big bank of 24V batteries.
Now you can go hurt yourself
  #24  
Old Thu 01 March 2012, 08:22
revved_up
Just call me: Craig
 
Hartland, MI
United States of America
I think the saddest part of this thread is that it got so quickly out of control. Mark asked an electrical question and as usuall Mike was the first to chime in as he always does with great advice on anything electrical. Mike was concerned with the voltages and the scope of the project not being a do it yourself for safety reasons and from there it all went down hill. I think Mikes first response was correct and as always the advise was right spot on.
  #25  
Old Thu 01 March 2012, 11:17
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
After doing a lot more reading about DC brushless motors, and after taking apart one of my DC fans that is actually a DC brushless motor, I've learned that those motors are sort of a hybrid stepper that is similar to a servo motor. Many of those motors are rated by their maximum current draw. The maximum current draw is a rating mostly used to show how much current the motor will draw for a few milliseconds. Sustained current draw at the maximum level will quickly burn the motor up. My DC brushed motor driven by a Geckodrive servo driver has a 7A continuous rating and a 20A instantaneous rating.

The question about power supply is less important than the question that should be asked. That question is, "How do you drive a DC Brushless Motor?" The motor requires pulses, like a stepper motor. Drivers for those types of large motors are expensive and complicated.

I see no reason to use that type of motor as a spindle when AC spindles and VFD are easily obtained, relatively inexpensive, and more suited to a CNC machine (just look at the spindles used on the "big-iron" machines).

Changing the paradigm isn't always a good solution.
  #26  
Old Thu 01 March 2012, 11:31
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
How did I miss this thread? Guess I have been busy.
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