Motor starters

When is star-delta, Dol or VFD starters used for the motor? How many times the current rating of the motor wil be drawn on a Dol starter if no OLR used?

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ibicelectrical

  • Oct 31st, 2008
 

If there is a load like conveyor belt, chain drive, etc. then there is considerable time required by the motor to start and come to required load, so there is large current requirement at the time of starting. So to reduce this starting current we use star-delta starter. If there are no such loads present then upto 110kW we can use DOL starters.
In case of VFD, first, it is required by Process people to control the flow of their liquid, etc.
Second, now a days it is also used for controling the speed/current of the cooling tower, boiler pumps,etc. as they have the fluctuating loads.
Third, these can be used in addition with the UPS for emergency backup, during this period the DG can start and then the UPS will be by-passed. In between the loss of supply and staring of DG, the UPS supplies the load through VFD.

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