Testing Canstack PM Motors at Higher than Rated Frequencies
Testing Canstack PM Motors at Higher than Rated Frequencies
(OP)
I'm trying to determine if testing small synchronous PM motors (used as timing devices in appliance controls) at high frequencies (up to 600 Hz) will damage the motor during production audit testing. These motors are rated at 115 VAC 60 Hz with a speed of 0.0037 RPM (1 RPM/271 minutes). In order to get the test completed in a timely matter the motors are thus running at 10X speed. How does increasing the frequency affect the excitation level, the voltage, and current from a theorical standpoint?





RE: Testing Canstack PM Motors at Higher than Rated Frequencies
1. Which parameters are you testing at these motors?
2. The higher frequency will cause Eddy Current to increase and generate heat and watt losses.
3. Remagnetization losses will increase with frequency (C. P. Steinmetz's Law/Formula)
4. Bearings may be damaged by the higher frequency causing common mode currents. Some good grounding may be prudent.
5. Permanent magnet may lose some magnetism due to higher temperatures.
6. Some increased mechanical vibrations may develop.
7. Wire skin effect will take place and heat up windings.
8. Etc.
RE: Testing Canstack PM Motors at Higher than Rated Frequencies
RE: Testing Canstack PM Motors at Higher than Rated Frequencies
Motor speed is 240 RPM. The timer speed is 0.0037 RPM with speed reduction from the motor to the timer cam achieved through a gear train. Sorry for the confusion. The test monitors timer operation only (motor start, correct motor rotation, and contact switching/timing). Individual motor voltage, current, and temperature are not recorded. I observed a customer's tester and the motors ran cool to the touch. The customer states that at the tester test conditions (208 VAC @ 600 Hz) motor current is half the level it is at 115 VAC. I'm not sure how they can maintain the motor excitation level. We are trying to develop a similar tester.