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Home » Motor protection » Voltage transient in induction motor
Voltage transient in induction motor
Voltage transient occurs whenever there is a sudden change in current in an inductive device. Inductors resist a sudden current change.
V=L di/dt
In electric motors this occurs at start up when the contactors close and shut down when the contactors open. Soft starts reduce the start up transient, but, not the shutdown transient.
This also occurs with variable speed drives which switch the current rapidly and repeatedly.
Voltage transients of 2 to 5 times line voltage are common. This is a primary reason for failure of weakened motor insulation systems. Test standards require high voltage Hipot and Impulse testing of insulation systems in order to ensure that a motor can withstand these transients.
V=L di/dt
In electric motors this occurs at start up when the contactors close and shut down when the contactors open. Soft starts reduce the start up transient, but, not the shutdown transient.
This also occurs with variable speed drives which switch the current rapidly and repeatedly.
Voltage transients of 2 to 5 times line voltage are common. This is a primary reason for failure of weakened motor insulation systems. Test standards require high voltage Hipot and Impulse testing of insulation systems in order to ensure that a motor can withstand these transients.