Effects of 50 hertz on 60 hertz 1-phase and 3-phase motors 1

[EuropeHurdles]

In Europe, can anyone explain to me if it is harmful for a 60 hertz single or three phase motor to be connected to 50 hertz power source, even if the voltage is stepped down via a transformeer to be the voltage required by the motor?

 

[Skogsgurra]

The 60 Hz three-phase motor does not have many problems if the frequency and voltage are reduced to 50 Hz and U60*50/60. The torque will be the same, power will be reduced to P60*50/60 - but there might be a problem due to reduced cooling. This is normally not a problem.

The single-phase motor has its own problems. If there is a start/run capacitor it may be a bit off its optimal value when the frequency is changed. The problem is worsened by the fact that capacitive reactance goes up as frequency is reduced while the inductive reactance in the motor goes down. Increasing the capacitance with 40 - 50 percent usually restores balance and permits normal operation.

 

[aolalde]

Skogsgurra described the reverse of your question. 60 HZ motors operated at 50 Hz.

50 HZ motors operating at 60 HZ: The speed will increase 20% but in general both motor types could perform quite well except for some extra iron losses easily handled by the extra fan cooling due to speed increase.

For three phase motors it is convenient an increase of voltage proportional to the frequency change (60/50) other way the flux is too weak and the speed-torque curve drops with the squared ratio of the flux reduction.
For instance a 380 Volts 50 HZ motor will work at 380*60/50 = 456 V or the STD 460 V 60 HZ in USA. To extend the life use a conservative same power demand (HP).

For single phase motor a voltage match could be not possible for 220 or 120 VAC, this could weaken the motor too much unless you do a re-winding. Other way, you expect similar performance and recommendations as a 3-phase, the other possible problem is the centrifugal switch cutting the starting circuit at 5/6 of the operating speed. This will not be a problem unless a very high torque demanding load is coupled to the single phase motor.

 

[aolalde]

I apologize. I am describing the reverse situation to you question.

 

[ccjersey]

Well now we have it all in one thread! Which ever way one wanted to go, you both have covered it.

Jim