I have imported a hydraulic power unit from Canada. The problem is that the motor is designed for 60Hz frequency but we have 50Hz. Now when we plug in the motor it makes alot of noise and vibration. It gets heated up as well. Now I was thinking to use single phase VFD that will take input of 50Hz and will give output to 60Hz. I just want to confirm before buying VFD that can it work ? and if there would be any effect torque and efficiency. Please share experience if someone has any

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    \$\begingroup\$ An easier solution could be reducing the voltage. U/f has to remain constant. Your motor has 220V/60Hz=3.67=183V/50Hz. The torque stays the same but the drive speed is only 5/6. The power is lower because of that. \$\endgroup\$ – Janka May 13 '17 at 20:44
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    \$\begingroup\$ If you can find a 220:36V transformer rated for the motor current you can use it to buck the 220VAC and give you about the correct voltage, as @janka suggests. It should be about 1/5 the size of a 220:180 VAC transformer with the same current rating. \$\endgroup\$ – Spehro Pefhany May 14 '17 at 3:03
  • \$\begingroup\$ Thank you for the replies, I hope the mentioned suggestions give me desired results. Reduction in speed is not a problem for me the only concern is the power and smooth running of the motor. \$\endgroup\$ – MGD May 14 '17 at 9:48
  • \$\begingroup\$ I have one little question if I need to replace the capacitor as well that comes with it? \$\endgroup\$ – MGD May 14 '17 at 9:53
  • \$\begingroup\$ This is almost always a "consult with the factory" matter. Is the motor a commodity, easily changed standard size? Worth a check. Keep in mind the machine was built for a motor spinning just shy of 1800 or 3600 RPM... and on your power, it'll spin just shy of 1500 or 3000 RPM because of the nature of your power. So a pulley/gearing change may be a factor. \$\endgroup\$ – Harper May 14 '17 at 13:39

If the motor is a single-phase motor, use with a VFD is very limited. The very few brands on the market will only work with permanent-split capacitor and shaded pole type motors. They don't provide very high starting torque and have been limited to use with fans and pumps in the past. Better capability has been recently advertised, but limitations should be carefully investigated.

VFDs with 3-phase motors can usually provide torque at any speed that is comparable to power frequency operation in most respects. Continuous operation at less than 1/2 to 3/3 speed may be limited due to motor self-cooling concerns. The waveform will reduce efficiency and increase operating temperature only slightly. With motors not rated for VFD use, voltage spikes generated by the VFD can harm insulation, but that is not usually a concern with 220 volt motors.

There is very little risk in using a transformer to reduce the voltage to the proper voltage for 50 Hz as suggested by @Janka. The only disadvantage is the 20% speed reduction from the design speed of the driven equipment.

  • \$\begingroup\$ Starting torque is not that much required as the delay in applying pressure can be adjusted with the hydraulic valve configuration. It can give 2-3 seconds before the motor reaches its peak torque. does it make VFD feasible then ? \$\endgroup\$ – MGD May 14 '17 at 9:57
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    \$\begingroup\$ Since you asked about a capacitor in another comment, you must have a single phase motor. The delay in applying the load will remove the starting torque concern with a single-phase output VFD. You need to make sure that the capacitor remains connected all of the time, is not disconnected when the motor reaches full speed. \$\endgroup\$ – Charles Cowie May 14 '17 at 12:32

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