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fyffe555
07-25-2003, 12:09 PM
OK, I'm confused about these steppers; Powermax II P21NxxC-Lxx hybrid series. what Voltage and current should you be running these at?

I think a few guys are using similar motors here so hopefully somone can tell me whats what. I have the pdf's that relate but the numbers do not add up. Cannot figure out what voltage I'll need and what power supply to build so haven't spun anything yet.

The motors measure 1ohm per phase.

On the label it states 1.75a bipolar series. PDF agrees and further says 3.5a bipolar parallel and 2.5a unipolar.

Label says power Po= 46W, Vs(dc) 65v & 1500rpm Is that 46w total for all phases? 65v doesn't make sense and can they really do 1500rpm? intend using ten tpi so aiming for 600rpm max

What ever, if you take 1.75a, 46W and 65v Ohms Law has a fit and it doesn't make sense, to me at least. If you take 1.75a and 1ohm then thats 1.75Vdc? If you take 46w/4 phases and sqrt(W*ohms) then thats about 1.7v.

So am I right to think that a 12v motor supply, current limited to 1.75a or whatever is going to work without letting out the magic smoke?

thanks

ger21
07-25-2003, 12:38 PM
What driver are you using? For best performance, run them in parallel at 3.5a and as high a voltage as you can up to 65V, if your driver can handle it.

Gerry

kong
07-25-2003, 01:02 PM
As ger21 said, use the highest amperage your driver card will support. There are some wiring diagrams over on the Xylotex (http://www.xylotex.com) website for the different configs. I'm using the xylotex board, and have them wired bipolar series (1.75A), and they are mighty good.

fyffe555
07-25-2003, 01:07 PM
For the fun of it I was intending to build my own drivers/PS once I knew what I needed to output.

In the interim I have some IM483's which can output 3A rms 4A peak and 12-48vdc.

What relative performance could I expect with these motors in Parallel, Serial and Unipolar? they're supposedly 116ozin in Bi and 82ozin in serial but the torque curves drop off really fast in Bipolar and Unipolar seems to have higher torque in the 200-800 range?

thanks

Andrew

bcromwell
07-25-2003, 01:40 PM
Originally posted by kong
As ger21 said, use the highest amperage your driver card will support. There are some wiring diagrams over on the Xylotex (http://www.xylotex.com) website for the different configs. I'm using the xylotex board, and have them wired bipolar series (1.75A), and they are mighty good.

Am I reading this correctly, Pins 1&2 (A) 3&4(B) Are what is required for this stepper to be Bipolar?

kong
07-25-2003, 01:48 PM
No, all eight pins are used, read the "installation bulletin" and it gives the pin outs of the motors, and how to wire them for series/parallel.

bcromwell
07-25-2003, 02:41 PM
Originally posted by kong
No, all eight pins are used, read the "installation bulletin" and it gives the pin outs of the motors, and how to wire them for series/parallel.

Ah I see it now, Thanks, I must have been looking at a 4 wire motor diagram.

ger21
07-25-2003, 03:17 PM
Bipolar parallel will give the best performance. The higher the Voltage you feed them, the slower the torque drops off, so go with the highest possible voltage.

Gerry

fyffe555
07-30-2003, 01:11 PM
Gerry, Thanks for the replys.

Have you anything to suggest about the Watt ratings? The pdf and the label both state 46W. 3.5a and 46W is only about 3.85V? How's that work? Is that 46W per phase? Hence my original post.

I'll be using a PWM driver with current limiting so I guess I'll just wire one up and see how it goes?

Is anyone else using these motors? If so what are you running them at?

Thanks again.. Now back to figuring out how to mount the end bearing and motor couplings....

ger21
07-30-2003, 03:33 PM
Use the 3.5a and as high a voltage as you can supply, most people use around 24V. The motors have a 65V max. As long as you don't exceed the rated current for the wiring type chosen (parallel or series), you shouldn't have any problems. I always assumed that if you take the numbers in the .pdf, a*ohms = V, but after thinking too much I'm not positive that is correct. But if you stay at 24V or less, V shouldn't matter . Does this help?

Gerry

fyffe555
07-30-2003, 04:37 PM
Gerry,

Yes it helps, thanks. As you say the numbers do not add up and it helps to work this through. I'll guess I won't really know until I end up spinning a motor and try a few wiring and power permutations and see what happens.

Andrew

balsaman
07-31-2003, 12:33 AM
Andrew,

Everyone runs steppers at something much greater than the rated voltage. Then they use resistors or a chopper circuit to control the amps. It's the amp that make heat. The 65 volt rating on those motors is just the max volts the motors should see. They are actually ~1.7 volt motors and if you hook them up to 1.7 volts they will draw the rated current. The ohms law thing does indeed apply to these motors (and everything else).

The best way to run steppers is use the highest volt powersupply the driver can handle (65 volts max for these motors), and then set the current on the driver.

If you are using a xylotex driver the max is 30 volts or so. Use a 24 volt supply. The xylotex will handle the current limiting.

Eric

bunalmis
07-31-2003, 03:35 AM
Motor labels show the mechanical powers. 46W is not electrical power.

" What ever, if you take 1.75a, 46W and 65v Ohms Law has a fit and
it doesn't make sense, to me at least. If you take 1.75a and 1ohm
then thats 1.75Vdc? If you take 46w/4 phases and sqrt(W*ohms) then
thats about 1.7v."

This is wrong electrical power higher than mechanical power and you need the efficient of motor.

You can not use the ohm law for motors because this is valid
only pure resistive loads. If it is true motor gives only termal
energy.


I want to give simple DC motor example.

You can not calculate P = V*V/R = 12*12/1 = 144W Wrong

P = (V - EMF) * R * V = (12 - 9) * 1 * 12 = 36W True

If eff 0.6 Mechanical power is 36 * .6 = 21.6 W

You can not live any problem if dosnt exceed the current limits
at your application. Use PWM type current source and you can use 65V.
and you dont need current limiter resistor at this configuration.

boxwood
08-27-2003, 08:19 PM
Hi All

Balsman wrote
Everyone runs steppers at something much greater than the rated voltage. Then they use resistors or a chopper circuit to control the amps. It's the amp that make heat. The 65 volt rating on those motors is just the max volts the motors should see. They are actually ~1.7 volt motors and if you hook them up to 1.7 volts they will draw the rated current. The ohms law thing does indeed apply to these motors (and everything else).

Can someone please simply this for me and briefly describe the math behind it

I will be using a 24 volt 12 amp supply using a hobbycnc unipolar controller outputs 1.25amps and will have 3 of these motors
with 2 resistors per motor what ohm and watt resistor should I use ? or can I even use these motors on that setup?

Thanks
Rau

cnczane
09-05-2003, 02:33 PM
This is what I've gathered from the posts & web:

Higher voltage means Faster rise times--means snappier performance.

Higher currents means Stronger torque--means beefier performance.

Higher voltage means Higher coil currents--means you must take steps to protect the motor by limiting the current.

Elegantly dumb way: put in BFRs (big fat resistors) in series with coils. Wastes power. (I'd expect performance costs for doing things the dumb way...)

Elegantly smarter way, if worth the cost: don't leave the current on all the time, but 'chop' it up so its average value is reasonable. Higher complexity & cost. (I imagine this is how one lands a great white shark on 20 lb. test line...)

In geckodrive.com's G201A manual, there's a recommendation that the power supply voltage be 4 to 25 times higher than the rating of the motor (while also staying within the 24 to 80V hard limits of the 201A).
(BTW, the 201A uses a 'current-sense' resistor, which I suppose is not to limit current, but rather to figure out what it is in order to do a better job controlling it.)

But what do I know? All I know is what I read on the web.
--
dnelson