[sds357]

I found some 8 wire Unipolar Nema 34 steppers that are rated at 5.5A and have a inductance of 2.7mH. They have a holding torque of 1005 oz-in.

So if I drive them with a G540 at 3.5A and 48 - 50 volts I should get 640 oz holding right? Am I missing anything? Is there any reason this wouldn't work ok?

[MechanoMan]

Unipolar cannot go on the G540. It's a bipolar driver.

BUT, if it's an 8-wire, it sounds like a bipolar- which can always be wired as a unipolar too (although you wouldn't do that for the G540).

The unipolar current rating is different than the bipolar.

[sds357]

well maybe the dealer put the wrong info in the title. The title is the only place that says unipolar. The manufacturers spec sheet doesn't say if it is unipolar or not. It does say that it has 8 wires plus a ground wire. The G540 manual says 4, 6, or 8 wire steppers are compatible.

[MechanoMan]

Well, yes you can use a stepper at a lower current than specified, for less torque. It will not get as hot.

If the seller's being ambiguous on the description, know this: the stepper can usually be wired in series or parallel bipolar config. Parallel is twice the current at half the voltage compared to series. Generally we use the parallel config. But if that rating you got was for the parallel, then that'll mean the series is 2.75A and within the GD540's capability.

But, there's a reason we use the parallel config. In holding torque, there's no difference. But in parallel config, there's a LOT more voltage than needed to hold steady-state, and that allows for fast changes in winding current when stepped, which increases the high speed torque quite a bit.

Best to get the model of the stepper and Google the datasheet for it.

[nofx]

I have Parker 34nema 6.1 amp steppers and there rated at 540 oz in. Maybe the steppers are like a 1200 watt sony car amplifier but the rms is 200watts.

[johnmac]

Yes, you can use 8 wire steppers as bipolar. And yes, you can use them as mentioned. I'm not sure about the amount of power reduction, but they will work.

John