how frequency affects performance
If you operate the motor at 5/6 of the 60 Hz rated voltage, the motor can be operated continuously at rated torque. The operating speed will be 5/6 of the rated 60 Hz speed and the power delivered will be 5/6 of the rated 60 Hz power. The efficiency, power factor, current and temperature rise will not change very much. The life expectancy will not change very much. The self-cooling capability will be reduced slightly because the rotor fins or shaft-mounted fan will be turning at 5/6 the 60 Hz speed. However, the iron losses will also be reduced due to the reduced frequency and the friction and windage losses will be reduced.

If you don't operate the motor at the proper voltage i.e. 5/6 of rated 60 Hz voltage, the effect will be the same as operating any other motor at the wrong voltage.

Re Comment

The proper 50 Hz voltage for a 220-240V, 60 Hz motor would be 183-200V. A supply that is nominally 220V would be 10-20% high for that motor. Below is a graph showing the major effects.


Image by Ed Cowern