Help wiring M60STH88-3008DF Steppers Motors to 752 Drivers

[Robin Hewitt]

So what's the max current I should be using given my 43v supply and why am I using 43v when the data sheet says 5.46v?

As Jonathan says, you need it to overcome the inductance of the motor windings.

Inductance tells you how unwilling a circuit is to change the flow of current. It's all about building up and collapsing magnetic fields.

You apply 43 Volts and the current in the coil changes a jolly sight faster than if you applied 5.46 Volts. This is really useful if you want to reverse the current in a stepper coil umpteen times a second.

When it switches the current off, the coil doesn't want to stop flowing current. If you don't give that current somewhere to go the volts will simply rise until a transistor blows or ithe arcs to ground. Seriously bad idea. The fix is to allow the current to flow back to the start of the coil, round and round until the coil resistance turns it in to heat. Thus the coil inductance is a double whammy, it gets you when you turn the power on and when you turn the current off.

Luckily the driver sorts it all out for you. Some are cleverer than others though. Ignore everything on the motor label except the current.

Of course what you really need is the graph which shows motor torque over a speed range for a given current and voltage. Unfortunately the sellers of stepper motors have realised that the only thing their customers seem to care about is the holding torque so that is what they sell you. Who cares if the torque nose dives at 5rpm? It's a 3Nm motor, has to be good, dunnit!