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Current in I/M

Guest Anonymous

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A 3-ph. Induction Motor of 22kW at 0.8 pf is used for constant load of 20kW. what will be the starting and running current in motor for:

1. Star connection.

2. Delta Connection

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I assume that this motor is designed for use in delta.

It is not possible to determine the start current from the information given.

In delta, it will equal the LRC and in star it will be one third of LRC.

(LRC typically 600% - 900% of rated current) In this case, I expect that the motor would not reach full speed in star due to the load.


The running current in delta will be the power divided by the voltage, divided by the power factor, divided by the efficiency. You do not supply enough information to work this out.


The motor will almost definitely stall in star at this load.


Best regards

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  • 3 weeks later...

If the motor is running at full speed, then the current drawn will be a function of the shaft torque and the magnetising current.

If these are known, then the current in star, and the current in delta can be estimated provided that the efficiency and power factor are also known.


Best regards,

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