Using a 60Hz motor in 50 Hz supply..

[Indian]

Assuming that a 220V,60 Hz motor is hooked to 220V,50 Hz supply , what will the effect on performance be ?

[astro]

Motors: Changing between a 50 and 60Hz supply.

Using a 60Hz motor in 50Hz duty.
w) It will turn 20% slower.
x) Cooling will drop dramatically.
y) The load’s horsepower requirements will drop, possibly dramatically.
z) V/f will increase possibly causing a large increase in current draw.

Make sure the load will still do what is required of it when running slower. For instance, a fan load would now move less air. Still enough?

The cooling will reduce dramatically. Is it enough to matter? This depends on how the load has decreased. If the hp requirement dropped because the load has decreased the current will drop and less heat will be released internally. You would want to take temperature measurements until the motor reaches a steady state temperature running in its new frequency application.

The motor’s hp will drop because hp is a function of speed x torque. The motor’s torque doesn’t change but its speed has dropped so it is now a lower hp motor. If you change pulley sizes to return the load to its original speed your motor will likely be undersized, possibly seriously. Example: A 10 hp motor is now an 8 hp.

The most serious issue is the V/f issue. The V/f will increase. Likely enough to cause a large increase in the motor’s current. This coupled with the reduced cooling may cause rapid overheating. However the V/f problem can be fully mitigated! You reduce the voltage to the motor by the amount required to return the V/f back to its original value. This removes the hazard of excess current from an increased V/f.

Example: A 60Hz 240Vac motor is going into 50Hz service.
V/f = Y Hence: 240/60 = 4.0

So if Y x f = V then by plugging in the new frequency of 50 we see:
4.0 x 50 = V
V = 200
Running the motor at 200V at 50Hz will remove the V/f problem.

Another way to think of this is:
New voltage = Old voltage x 50/60
New speed = Old speed x 50/60
New Horsepower = Old horsepower x 50/60
Note: This would instead be 60/50 for a 50 to 60 Hz conversion.

[Indian]

Astro ,

thanx for the link and reply…