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In Rush Current And Starting Current


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What is the difference between inrush current and starting current of an Induction motor?

What is the relation between them ?

Some manufacturers offer motors with low in rush current.In actual terms they or offering double cage motors or rotors with narrow slots which has lower starting currents.Does these motors have low switching currents?

It appears they are using terms starting current and inrush current synonymously.

Are they justified?

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Hello subrao


The inrush current is the current transient that flows in the first cycle or so that establishes the magnetic field in the iron.

Once the field is established, the current falls to the steady state starting current until the speed of the motor approaches full speed when the current falls to the current required to drive th load.

The inrush current can be significantly higher than the locked rotor current with 2 - 2.5 times the start current being quoted by some.

The inrush current is more about the stator magnetic field than the rotor, so I do not think that the rotor wil have a significant influence on the inrush current, rather the level of iron flux and the material of the stator laminations will be important.


Best regards,

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