MechMate CNC Router Forum

Go Back   MechMate CNC Router Forum > Electrical & Electronic > 702. Power Supplies
Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Reply
 
Thread Tools
  #31  
Old Fri 26 September 2008, 04:31
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The transformer that was being monitored was supplying 50V AC and powering 4 gecko's limited to 2 Amp each. The peak current draw on the transformer occurred during jogging and not during any cutting. That peak was 2.8 Amp (140VA). Then one day there was nasty running into stops at full speed and the meter held a reading of 4.5 Amp after the shouting died down. (225 VA)

This testing proved something we knew all along . . . . . a 300VA transformer happily drives this table without getting warm.

Based on the above, we commited a local tranformer maker, Toroidal Technologies (tel 011 615 7245), to produce 4 transformers to the following spec:

300VA toroidal power supply transformer:
Primary: 230 VAC single phase
Secondary A: 28 to 30 VAC, 9 Amp max (for the Gecko's driving half-coil PK296A2A-SG7.2 motors)
Secondary B: 8.5 to 9.0 VAC, 1 Amp max (for the PMDX-122 (and rectified for the limit switches if needs be)

(Price approx $47ea)
Reply With Quote
  #32  
Old Fri 26 September 2008, 06:11
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Correction: The crashing didn't raise the amps. It was the re-start after the E-stop that did it. That was the inrush current to a partially discharged capacitor.
Reply With Quote
  #33  
Old Wed 13 January 2010, 05:03
sprayhead
Just call me: Francis
 
sydney
Australia
Just to be double sure now, I will use 2 motors rated 4.2 amps per phase and 2 rated 4.5 amps per phase. Connections will be bipolar half-coil with G203's.

9+8.4 = 17.4amps total sum

17.4 * 0.67 = 11.6 amps

Is this formula still current?

Based on this, I am planning on ordering an Antek power supply with a 40V AC 600VA toroidal transformer.

Or, could I order 500VA power supply? It's a great deal cheaper.

thanks,
francis

Last edited by sprayhead; Wed 13 January 2010 at 05:07..
Reply With Quote
  #34  
Old Wed 13 January 2010, 05:22
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Francis, I think all the evidence above shows that the formula is too conservative; you could probably get away with a smaller transformer. So your choice will work (you checked the inductance, on both types of motors to calculate your voltage, right?).
Reply With Quote
  #35  
Old Wed 13 January 2010, 05:32
KenC
Just call me: Ken
 
Klang
Malaysia
Francis, Its been mentioned many times in this forum (can remember which thread) that 300VA tranny is sufficient for the job. There will be a big saving in $ & space.
When you use unregulated power supply, the tranny will only supply when the motors as for. & most of the time they don't draw peak current & even more rear that all motors draw peak current at the same time.
Reply With Quote
  #36  
Old Wed 13 January 2010, 06:01
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The Power Supply needs only to supply 2/3 of the rated motor current <==== This addresses the 0.67 factor
Reply With Quote
  #37  
Old Wed 13 January 2010, 21:49
javeria
Just call me: Irfan #33
 
Bangalore
India
Francis I have used a .75 factor and feel that I have wasted it - it is hardly anyday over the ambient room temperature

i have just wasted more money there - I also consulted with Anil who has a good command over electrics and electronics and his suggestion was for 0.5 factor and that too I think will never get hot

RGDS
Irfan
Reply With Quote
  #38  
Old Wed 13 January 2010, 22:20
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
There are a couple of threads and posts that should be moved to the archives because they gave the wrong idea on the transformer size. I am glad that we are now getting more real life reports from actual routers being driven.
Reply With Quote
  #39  
Old Wed 13 January 2010, 22:30
Castone
Just call me: Leo #41
 
Soddy Daisy , Tn
United States of America
I am running a 51 volt power supply and I am not using any resistors and my motors seem to be just fine no over heating . Sugested power supply was around 45 volts.
Reply With Quote
  #40  
Old Wed 13 January 2010, 22:36
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Leo, are you saying that you are not using resistors on your geckos? (Because I can't think what other resistors you might be using)
Reply With Quote
  #41  
Old Thu 14 January 2010, 03:10
sprayhead
Just call me: Francis
 
sydney
Australia
Quote:
Originally Posted by bradm View Post
Francis, I think all the evidence above shows that the formula is too conservative; you could probably get away with a smaller transformer. So your choice will work (you checked the inductance, on both types of motors to calculate your voltage, right?).
Hi Greg
Yes I have checked the inductance and applied the formula (sqrt of inductance * 32 = max. power supply voltage.)

Quote:
Francis, Its been mentioned many times in this forum (can remember which thread) that 300VA tranny is sufficient for the job. There will be a big saving in $ & space.
When you use unregulated power supply, the tranny will only supply when the motors as for. & most of the time they don't draw peak current & even more rear that all motors draw peak current at the same time.
Hi Ken
I did see all that evidence but I was a bit "scared" as I will be doing 3D work all of the time.

Quote:
Francis I have used a .75 factor and feel that I have wasted it - it is hardly anyday over the ambient room temperature

i have just wasted more money there - I also consulted with Anil who has a good command over electrics and electronics and his suggestion was for 0.5 factor and that too I think will never get hot

RGDS
Irfan
Hi Irfan,
You were even more worried that me about power supply! .75 factor is huge.

Thank you for the input, I think I will end up going slightly bigger then .5 factor, wich calculates to a 500VA tranny for me.
Reply With Quote
  #42  
Old Thu 14 January 2010, 06:12
Castone
Just call me: Leo #41
 
Soddy Daisy , Tn
United States of America
Gerald, yes that is what I meaning to say. This was the original thoughts.from the forum.

The KL34H280_45_4A motor has 6.8 mH inductance, It can be used with power supplies up to 80VDC (32 X SQRT(6.8) = 83VDC. 80VDC is the MAXIMUM voltage that the Gecko stepper drivers can handle.) 18 amps would all full speed under all conditions.

The KL34H280-45-8A motor has 2.2mH inductance when wired either half-coil or bipolar parallel. It can be used with power supplies up to 47VDC, using that same formula shown above. 25 amps would allow full speed under all conditions.

I would use a 70VDC power supply for the first motor to allow for power line variations. I would use a 35VDC to 40VDC power supply for the second motor, also to allow for power line variations.

I am wired up bipolar parallel.
Reply With Quote
  #43  
Old Fri 15 January 2010, 04:37
KenC
Just call me: Ken
 
Klang
Malaysia
If for any reasons that you must use an Antek tranny, Oriental motor, and Gecko Drivers; It is ok to run the motors at lower voltage to suit the Gecko max voltage rating or lower... This will lower the max speed, I wouldn't know how much lower but my gut feeling tells me they will be fast enough for the job. even at 35~40Vdc
Reply With Quote
Reply

Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 04:46.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.