# Convert motor running frequency from 50Hz to 60Hz?

Assuming that you checked the mechanical properties and the centrifugal force at the rotor at the higher speed from 50Hz to 60Hz, and they are OK, then you have to consider that the flux in the machine will go down by the ratio of the increase of frequency to 60Hz. Also the inductances will increase, so locked amps will be down, Locked rotor torque will be down, power factor will change, and efficiency will change. No load amps will decrease. If you want to change the electrical design to make it like it was for 50Hz then you have to increase the number of turns of the motor, but you have to know what you are doing.

Please note that except the change in the asynchronous speed of the motor machine, many other parameters will change. This will include the effective phase impedance of the motor, the current/voltage levels, etc. Also, please note that the torque-speed curve and the associated efficiencies will be affected by the change in frequency 60Hz to 50Hz.

The required number of turns will be reduced. Also, please note that due to the change in frequency, it is the IMPEDANCE that will vary and not the INDUCTANCE. Regarding the motor efficiency, this is kind of complicated which needs more information about the specific machine. The efficiency will not only be affected by the change in the number of turns, but will also be impacted by the change in base frequency since the change in frequency will result in a change in your core/iron loss.

I was looking at a 110 HP motor that I used to see what was changing with the change in frequency, and I wrote incorrectly inductance, but I was reading impedance in ohms. He is also correct in that the turns should go down. In my example I had originally 400 volts 50 Hz with a winding of 5 turns, 2 circuits Delta and the redesign was 400 volts 60 Hz with 4 turns, 2 circuits Delta.

You have to be very careful because changing your turns changes your impedance, your Locked rotor amps, your locked rotor torque, your no load amps. In the example that I was doing, the power factor at full load went down, and the full load amps went up when converting 50Hz to 60Hz.

If you are using an existing machine at different frequency, without a constructional change, the considerations and answers would be different. Then you changed over to rewinding or reconstructing the machine, it becomes a normal design at a different frequency (50Hz or 60Hz), and then you shifted to specific voltage. They do not change if you don’t change number of turns or any other physical part of the motor. The reactances change with frequency from 50Hz to 60Hz. I would like to calculate the motor parameters of the motor you are working on.

Please note that except the change in the asynchronous speed of the motor machine, many other parameters will change. This will include the effective phase impedance of the motor, the current/voltage levels, etc. Also, please note that the torque-speed curve and the associated efficiencies will be affected by the change in frequency 60Hz to 50Hz.

The required number of turns will be reduced. Also, please note that due to the change in frequency, it is the IMPEDANCE that will vary and not the INDUCTANCE. Regarding the motor efficiency, this is kind of complicated which needs more information about the specific machine. The efficiency will not only be affected by the change in the number of turns, but will also be impacted by the change in base frequency since the change in frequency will result in a change in your core/iron loss.

I was looking at a 110 HP motor that I used to see what was changing with the change in frequency, and I wrote incorrectly inductance, but I was reading impedance in ohms. He is also correct in that the turns should go down. In my example I had originally 400 volts 50 Hz with a winding of 5 turns, 2 circuits Delta and the redesign was 400 volts 60 Hz with 4 turns, 2 circuits Delta.

You have to be very careful because changing your turns changes your impedance, your Locked rotor amps, your locked rotor torque, your no load amps. In the example that I was doing, the power factor at full load went down, and the full load amps went up when converting 50Hz to 60Hz.

If you are using an existing machine at different frequency, without a constructional change, the considerations and answers would be different. Then you changed over to rewinding or reconstructing the machine, it becomes a normal design at a different frequency (50Hz or 60Hz), and then you shifted to specific voltage. They do not change if you don’t change number of turns or any other physical part of the motor. The reactances change with frequency from 50Hz to 60Hz. I would like to calculate the motor parameters of the motor you are working on.

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1. The synchronous speed will increase by 60/50.

2. The synchronous reactance will increase by 60/50.

3. S=12 MVA, The Power factor remains the same.

4. Ia increases by 60/50.

Thanks.