Locked Rotor current and beginning current that induction motor seems to it is in the same thing at very first glance yet it is not so. These room two various terms having different an interpretation and significance. In this article we will talk about the difference between the locked current and beginning current that induction motor.

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Locked rotor existing is basically the existing drawn by the motor at that is rated voltage once its rotor is preserved stationary or in various other words rotor is not spinning or rotating. So once we start a motor, that is rotor is already at rest. This means, beginning current and locked rotor current should be same. Isn’t it? No, the is no so. How?

See, motor deserve to be began using among the various starting methods. If the motor is started using direct Online (DOL) method, climate the voltage used at the terminal will be rated voltage that motor. As the rotor is at remainder during starting and voltage is rated voltage, the starting current will certainly be same to locked rotor current. Yet if any kind of other starting technique viz. Star Delta / Soft begin is used, then motor will certainly be began at a lower voltage (lower 보다 the rated voltage), hence beginning current will be less than the locked rotor current.


Another vital difference between them is the locked rotor have the right to be anytime throughout the operation of the motor. Because that example, take into consideration a engine running usually under the rated load. A sudden rise in load past its rating will cause increase in motor current and also hence raised motor torque. However if the fill torque need is more than the motor torque, the motor present will additional increase to increase its torque and will with maximum (equal come pull the end torque). If tho the load torque necessity is more than the pull the end torque, the motor speed will decrease to zero. This is the case of locked rotor. Over there are assorted other causes like jamming of engine bearing, pack jamming, single phasing of motor etc.

Thus locked rotor present can be attracted anytime depending on when the rotor is being halted or stalled when the beginning current is only taken throughout the motor starting.

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Locked rotor present should not persist for a lengthy time rather it may result in insulation failure due to overheating or may bring about buring that stator / rotor.

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