Electrical Engineering ⇒ Topic : Plugging
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Lalan
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Plugging :
After plugging has started, the best possible conditions occur when the motor stops, slip is unity, and the current and power factor are the same as when the motor is started with full voltage. Although the above conditions occur during a very brief period of time, they may cause disturbances in the supply and therefore, this as well as hovv- frequently plugging is required,must be considered before a decision can be made to as whether or not plugging is the best way of bringing a motor to quick halt. During the period of plugging, since the induced e.m.f. in the rotor is very high, the rotor current and thereby stator current are very high. However, braking current can be redued by inserting external resistance in the rotor circuit and as such wound rotor motors are beneficial as compared to squirrel cage rotor motors.
Plugging is advantageous employed in the case of reversing devices where braking and starting up of induction motor in reverse direction comprises stages of the same continuous process | |
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