Frequency inverters control the speed of three-phase motors. If one fails, the replacement need not be identical, but it must suit the motor, the supply and the control system.
The decisive ratings
The output current is decisive: the rated current of the inverter should at least equal the rated motor current. The power rating alone is not enough, because motors of the same power draw different currents. Supply voltage, number of phases and overload capacity for heavy starts are added.
For hoists and fast braking, the inverter needs a brake chopper with a braking resistor. For the swap, the parameters of the old unit should be saved or noted. Control signals and fieldbus connection must match the existing control system.
What a request for a frequency inverter should contain
- nameplate of the old inverter and of the motor
- supply voltage, rated motor current and power
- application: pump, fan, conveyor, hoist
- control: terminals, analogue signal or fieldbus
- braking resistor and line filter present or needed
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