VFD sizing for a 25 HZ 150 HP motor
VFD sizing for a 25 HZ 150 HP motor
(OP)
I have a 150 Hp 25 hz motor I would like to install a vfd on it to eliminate the MG set. My concern overheating/ overcurrent in the windings. Is it really an issue? will the speed setting to actual motor speed be say double if i set it up as a 50 Hz motor??
thanks in advance,Joe
thanks in advance,Joe





RE: VFD sizing for a 25 HZ 150 HP motor
Is your motor wound for 25Hz? if so, what voltage at that point and what are the amps at rated load?
What type of motor is it?
What is the application?
If your motor is already designed for 25Hz then the cooling arrangement would already have been taken into consideration but somehow I don't think this is right.
Best to advise what your nameplate says and work from there.
Do not rate a VFD on HP, especially with information on a motor that indicates it is special or you don't have enough information.
RE: VFD sizing for a 25 HZ 150 HP motor
Over speeding however comes with a host of other considerations, chief among which are the fact that once you go over base motor speed, the motor power remains constant and since speed is increasing, shaft torque goes down. At the same time if it is a centrifugal load like a pump, the POWER requirement will increase at the cube of the speed change. So at 50Hz, a centrifugal pump will need 8X the kW/HP as it does at 25Hz, yet your motor kW/HP will remain the same. You get in the weeds very fast with that. If your application is not a centrifugal load, then you still need to consider the loss of torque, and the speed rating of the bearings in the motor. it might not be worth it.
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