Motor voltages / cycles

[snorkles]

Have a 3 phase circulator pump motor(fractional HP)that is rated 220/380-418 volt @ 50 cycle.

Problem: Only availble voltages, are 208 and 460 @60 cycle

Please advise...

 

[electricpete]

Your volts-per-hertz would decrease (due to both V decrease and f increase), so core heating would be lower.

V decrease also causes slight overload but less than 10% so probably not a problem there (especially if motor is lightly loaded anyway).

The only possible problem I can see is that both factors also tend to decrease your available torque all along the Torque-speed curve. Possible problem that you may not be able to start your load or might stall when running if load torque gets too high. But why not give it a try and see how it works.

 

[snorkles]

Seems some euro communities are successfully utilizing USA motors using their 380-415v @50f .But what I really need to know is, is it possible, to run this euro 380-415v @50 cycle motor I possess, on a 460v @60 cycle feed . Or would it be better to configure it to it's 220v -3phase -50 f(euro) and feed it with a 208 3phase -60f . Or?
This is a very light duty heat circulator motor for a diesel genset.

Thanks for the input

 

[electricpete]

One important thing I forgot to mention earlier.... if you run the 50hz motor at 60hz, then the pump will run approximately 20% faster. For centrifigual pump with 20% speed increase, the flow should go up proportional to speed (approx 20% increase), the differential pressure should go up prop to speed-squared (approx 40% increase), and the power (current) should go up approx prop to speed-cubed (approx 60% increase). So a pump which might pump fine for a given fluid system resistance at 50hz might easily overload it's motor at 60hz. In that case the normal overload protection should trip the motor.

As to the choice of whether you want to select a slightly higher voltage than nominal (460v on 400v terminal configuration) or a slightly lower voltage than nominal (208volt on 220v terminal configuration)... I would pick the higher-than-nominal voltage (460v supply) since this tends to offset (compensate for )several of the effects of the increased frequency:
#1 - Increased frequency reduces available torque at a given speed, but increased voltage increases available torque. So picking the higher voltage (as compared to nominal) lessens the probability that you will have problems meeting load torque during starting or running.
#2 - Increased frequency increases speed which increases power demand as discussed above. However, higher voltage (as compared to nominal) will enable you deliver that higher power with less current and less I^2*R losses.

I'm assuming that the unit has the same nameplate horsepower rating regardless of which taps you select.

 

[electricpete]

I forgot to mention that the increased voltage results in slight increased risk of insulation failure. But it still seems like best alternative to me. (none of the solutions is perfect).

 

[teco]

snorkles:-motor would be wound for 400 volt 50 hz +-5%. the winding design would allow 460/480 volt 60 hz .output power and speed would go up but torque remains constant. as electricpete stated the load being a centrifical pump will go up. you now need to check the new absorbed power of the pump at the new speed .
kind regds.