# Controlling a Motor for test bench

This is my 1st question here and I'm stumped... I spent all my EE classes on programming and ICs. When it comes to AC and motors, I feel worse than ignorant and spent all day trying to research where to begin researching. I know this is a broad ranging question, but please get me pointed in the direction to get this going.

End goal: to have a multiple speed rotating shaft to test ignition systems.

Question: what are the parts/modules/equipment I need in addition to one of the below motors to make the test bench's shaft (1 pound) spin at 1000, 4000, and 7000 rpm?

I have 2 AC motors. I believe one is a stepper motor:

... and the other is an inductive motor:

For a previous project, I rigged up the inductive motor to work while connected to 115VAC (fused and switched) but it had to be manually spun up to start and had less power than the mass of this all would suggest, making me believe I was doing it incorrectly. It got the job done and didn't get hot, so I ran it.

For my test bench, I'll be using aluminum plate to mount everything and likely employ a belt drive. I have a Rapman and already can see that I could buy an Arduino and hopefully convince it to control the top motor in the same way the Rapman uses servos to drive its axes. Towards that end, I could get a gearbox for the motor (looks like this is compatible) and some kind of controller.

I've got a sig gen, an o'scope, milling machine, lathe, computers, pretty much everything but the practical experience to kick this off. Based on the size of my motors and the size of the ones in the Rapman, I'm confident the motors above have the power and size to accomplish what I'm after. Any help appreciated, thanks.

• A more precise description of what you need to do would help. Do you want variable speed 1000-7000, 3 speeds from one unit 1000 or 4000 or 7000 with some sort of changeover or a unit capable of one of those speeds. "One pound" may mean 1 ft.lb torque? Motors are marked 40 Watt and 70 Watt. Power ~= RPM x kg.m torque. At 7000 rRPM you can get 70/7000 = 0.01 kg.m ~= 0.07 ft.lb torque. Is that enough? 1 ft lb at 1000 RPM =~ 140 Watts. Faster is more. – Russell McMahon Jun 27 '12 at 2:01
• 1000 or 4000 or 7000 with some sort of changeover is what I'm after; I'll make waveform tests of the ignition system in a steady state. Varying speed dynamically is not required. "1 lb" is the total weight of the rotating mass (not exactly, but that or less). – Chris K Jun 27 '12 at 5:29

You probably need a motor-run capacitor to make the AC induction motor work properly. It does say 8uF on the label.

Also, I really, really doubt the first motor is a stepper motor. It states 100V, 50/60 hz. 100V is the Japanese line voltage standard, and I have never seen a stepper motor with a specification in hz.

Edit Ok, the first motor is a 4IK25RGN-A. This is a 1/30th horsepower AC induction motor.

Realistically, neither of these motors are appropriate at all for a servo system. They both look to be fractional HP induction motors.

You can control speed of an AC motor with a variable-frequency drive. However, VFDs (and induction motors in general) do not have much 0 RPM torque, and don't provide control of the actual motor position, just the motor RPM.

Really, you need a brushed servo-motor, or a brushless AC servo-motor (or even stepper motors). All of these use a different mechanism to generate motion then an induction motor, which is actually a rotating transformer.

• Ah thanks. Additionally, is a "servo system" something I'm even after? Or would a servo system be appropriate for what I'm trying to do? – Chris K Jun 27 '12 at 5:29
• I stopped by anaheimautomation.com today and an engineer / sales rep is going to help me. I'm going to weigh and describe better what I'm trying to accomplish and he's going to make a recommendation. I'll update/edit/answer as more develops. Thanks! – Chris K Jun 28 '12 at 6:49