Frank67pa Posted November 5, 2009 Report Share Posted November 5, 2009 I have a 3 phase, two speed motor that is rated at 380 volt/50 Hz which is being used in a 460 volt/60 Hz application. I understand that this is not an issue since the V/Hz ratio is relatively unchanged. My question in in regards to kW rating, name plate amps and cosphi. RPM is easy enough to calculate, but I do not know if everything else is as easy as using the ratio of the frequency change. Can anyone tell me how to calculate the kW, amps and cosphi. The dataplate on the motor is currently: 380-400 volt / 50 Hz / 1460 RPM / 6.8 kW / 14.1 Amps / cosphi 0.84 380-400 volt / 50 Hz / 730 RPM / 1.4 kW / 5.1 Amps / cosphi 0.55 Thanks, Frank Link to comment Share on other sites More sharing options...

yuri Posted November 7, 2009 Report Share Posted November 7, 2009 I have a 3 phase, two speed motor that is rated at 380 volt/50 Hz which is being used in a 460 volt/60 Hz application. I understand that this is not an issue since the V/Hz ratio is relatively unchanged. My question in in regards to kW rating, name plate amps and cosphi. RPM is easy enough to calculate, but I do not know if everything else is as easy as using the ratio of the frequency change. Can anyone tell me how to calculate the kW, amps and cosphi. The dataplate on the motor is currently: 380-400 volt / 50 Hz / 1460 RPM / 6.8 kW / 14.1 Amps / cosphi 0.84 380-400 volt / 50 Hz / 730 RPM / 1.4 kW / 5.1 Amps / cosphi 0.55 Thanks, Frank Hello Frank. The kW rise (because voltage now is increased), Amp-s should remain the same, power factor will be less (because reactance increases as now Hz are greater): for the low speed some 0.45-0.5 for the high 0.75-0.8 Link to comment Share on other sites More sharing options...

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