Chris,
You can do it the fun way. Chuck your motor up in a drill-press, set your multimeter to AC vots, connect it to a motor winding and do some science! Let the drill-press rip and measure the voltage. Find out or measure your drill-press RPM. Divide your measured volts by RPM to get the step motor's measured voltage to get that motor's "volts/RPM".
Double the speed of your drill-press and you will read twice the AC volts on your meter. Do the experiment, find out if it's true.
The AC frequecy will be 60Hz at 72RPM, 600Hz at 720RPM and so on. The AC voltage will be 10 times higher at 720RPM than at 72RPM.
Set the drill-press to it's highest RPM, chuck up the motor in a vise, connect nothing to its leads. Go away for 10 minutes, then try to touch the motor. You will probably burn your fingers.
Why is it hot when no electricity has passed thru the coils (remember, nothing was connected to them so no current could flow)?
That is because this is an excellent demonstration of "iron losses". The quickly rotating magnetic rotor induced eddy currents in the "iron" of the stator and heated it.
Science does not require expensive and esoteric equipment. You can use something as simple as a drill-press and a multimeter. That and a pencil and notepad is enough to gather data and come up with reasons why you see what you see.
Mariss  |