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  • No : 22000
  • Release Date : 2018/08/22 16:30
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Consideration on power supply capacity

I am considering to control a 55 kW motor with the inverter. What is the basis of recommendation of the power supply capacity of 99 kVA (indicated on the catalog)?
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Answer

The inverter's power supply capacity can be calculated using the following equation:
Power supply capacity [kVA] = Motor output (kW)/(Motor efficiency × Inverter efficiency × Inverter power factor)

Since the inverter power factor changes depending on the power supply and wire impedance, we set it to 0.6 to 0.7 with some margin.
Therefore, if the power supply or wire impedance is large, or the power factor is improved by the power factor improving reactor, you can reduce the power supply capacity.
While the motor efficiency and inverter efficiency are usually around 0.9, they decrease as the inverter (motor) capacity becomes smaller and the ratio of the power supply capacity against the motor output becomes larger.
In addition, the power supply capacity may be different from the capacity of other driving devices, such as AC servo. This is because the total efficiency and margin are different.
Product Name
Inverter, magnet motor drive
Series
Others

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