What will be the motor power in case of starting with frequency converter compared with the power required by the load? e.g. A fan requires 560 KW motor. If starting with frequency converter, should i increase the motor power rating? how much? and what are the reasons behind this?

 

Base on the recomendation from the manufacturer you should place one size higher than the Norminal Apply Motor for prevent undersize and overload problem either during Acceleration, Constant or Decceleration time.

Base on my experiences this is not necessary because most of the system manufacturer already consider this. So the same size of converter is enough to run either Acceleration, Constant or Decceleration unless you undersize the system.

Please email me if you need more infomation regarding converter.

 

The reason behind starting a motor with a softstarter (frequency converter) is to limit the starting current and also to lengthen the life of the windings and reduce structure stres on the motor. The other side is that you can fisically run the motor at a higher speed than normal operating speed.

 

as it was not that long ago that a company i have worked for made a similar change with a smaller motor the need came as they needed more out put from the fan and a conventional ac drive was implemented to carry out some form of speed increase as the load on the motor increased the input current also increased going from 50 hertz to 57 hertz made the motor run from a normal running current of 75 amps to a full load current of 125 amps a small change gave a large change in motor current 7 hertz was not much of a change i can not tell you the change in rpm your application will determine just how far you can push it also controlling ramp up speed also controlled start up current we had to allow up to 20 seconds to get to full revs under the old starting system it would have taken 13 seconds and reached up to 700 amps at starting so the ac drive was quite use full