Gecko G540 - local source

[Gary]

one thing you need to remember is it is not the holding torque you need but the torque at a given speed.
In most cases the holding torque is totally irrelevant.
Also if you under rate the current this will only really effect the torque at the lower speed range, and will have little effect at the higher speeds as this will be lower than the torque you would get at lower current.

Dont forget the lower the current means the higher the inductance and that means you need more volts to force the current through the copper. So spending more money for a 3.5A motor will in most cases give you less performance than using a 4.2A motor and running at 3.5A.
Without the volts you are choking the driver and you will not get a good performance.
People always forget about volts, and with a stepper system it is very important.

[crustybugger]

The one particular stepper I'm using is Pacsci rated at 845 oz in at the rated current of 3.3 amps which is what I set my drive at. It is a 4 wire series wound and has a phase inductance of 8.3 mh.
Experts seem to all agree that low inductance is required for the best performance and I have found that this is not the case.
Unipolar drives are also said to be inferior, I have been using such a drive on a small lathe set up for a production contract and had no problems at all.
Also, I have never been able to get the type of rpms from a stepper that are discussed on forums either using high or low inductance motors, unipolar or bipolar, series, parallel. I'm talking rpms that that are actually useful to drive anything.
I have purchased high end drives and quality new steppers over the years and never been able to get they speeds I read about, then again i'm a microstepping fan.
Regards