[Bryanpl]

Hi All:

Have a PowerMAx II stepper with the notation on the label 1.2amps. I have checked the resistance of each coil (4 coils) and they are approx 2.75 ohms each.

So can I assume the recommended voltage for the coils is 3.3v using half coil and 6.6v using full coil (2 coils in series).


Thanks

[ger21]

This might help you out. http://www.xylotex.com/PacSciDS.pdf does it have a model #?

[jeffs555]

Hope you find your motor in the literature that Gerry posted.

For an 8-wire motor, the current on the label is usually the single coil current. For two coils in series, you have to use less than the single coil current to keep from overheating the motor. Because the series connection has twice the resistance of a single coil, and power disipation(ie heat) is equal to resistance times the square of the current, you need to divide the single coil current by the square root of 2(ie multiply the single coil current by .707). The series voltage is therefore only increased by 1.414. If your drive can handle it, you would be much better off running the coils in parallel, and using 1.414 times the single coil current.

[ger21]

For an 8-wire motor, the current on the label is usually the single coil current.

My powermax motors list the series current rating.

[jeffs555]

My powermax motors list the series current rating.

Just curious Gerry, what are the Powermax numbers for your motors, and did they come wired for series connection? Most of the 8-wire motors I have seen had the single coil current on the label, unless they came with the connector already wired for series or parallel connection.

Jeff

[ger21]

M22NSXB-JDS-NS-02

They say 2.3A bipolar series

[Bryanpl]

Gerry: If the current is 1.414 times the single coil current and i am running in parrallel the resistance of the parallel coil becomes approx 1.3 ohms. Does this mean the rated voltage would be

1.2A series x 1.414 for parallel = 1.7A
2.7ohms per coil in series is 1.3ohms in parallel
so the rated voltage for parallel would be 2.21 volts

vs

2.7 ohm per coil x 1.2A = 3.25 volts for series


Thanks

Hope you find your motor in the literature that Gerry posted.

If your drive can handle it, you would be much better off running the coils in parallel, and using 1.414 times the single coil current.

[ger21]

No, current doubles for parallel vs series, and voltage is half for parallel vs series.

[jeffs555]

Like Gerry said, the series current is half the parallel current. Unless your motor label specifically says "1.2 amps bipolar series" or you find the motor in the link Gerry posted, the 1.2 amps is most likely the single coil current. In that case, the bipolar series current would be about .85 amps, and the parallel current would be 1.7 amps. The parallel voltage would be about 2.21 like you said, and the series voltage would be twice that.

[Bryanpl]

I looked at the label again and it has the following specs
P21NSXS-LSS-NS-04
1.16A Bipolar Series
Po 30W
Vs(dc)65

The exact model does not appear in their catalog and I sus[pect it is a OEM with special windings. However I have measured each coil and they are all approx 2.75ohms.

So can I asume if the current is rated as 1.16A Bipolar series the approx working voltage should be (2.75 x 2) x 1.16 = 6.38volts for a full coil.

[Bryanpl]

Thanks for the help, it's all starting to make sense now.

Here is a pic of the stepper and I plan on using it as is to dispense small amounts of liquid.

http://cgi.ebay.com/Fluid-Metering-I...QQcmdZViewItem

I don't imagine I will need a lot of torque, and from the specs I will only need to step the motor to from .5 to 2 rpm.

Any suggestions as to whether I should use full step, half step. Rather than parallel the coils, should I only use half coil?

Thanks greatly.

[jeffs555]

That looks right. The Vs(dc)65 spec would be the recommended supply voltage, which is about 10 times the actual voltage across the series coils. Most of the cheaper drives won't handle 65 volts, but you could get the same performance by running parallel at 2.32 amps with a 32.5 volt supply.

[jeffs555]

Can't get that link to work, but since you are not concerned with speed or torque, just about any driver would do, even unipolar. If you are concerned with smoothness, you might want a micro-step drive. There is really no advantage to running half winding over parallel. For the same current and voltage, they will give the same torque and speed.

[ger21]

The 65V is the max voltage. I think it's the same on all the powermax drives.

[Bryanpl]

Oops, guess the link is dead. here is the pic of the stepper. Reason I needed to pin down the current and voltage for the stepper is I am using a Rorze RD-021M driver and need to calculate the resistor for the current limiting (page 13).

http://netmotion.com/pdf/RD-021M8_E.pdf

I am a bit surprised that the value of the resistor typically is under 1 ohm. Is this normal for these type of drivers. I have used some online calculators for MOSFET drivers and they typically call for a much higher resistor.