What procedure does plugging refer to in the context of 3-phase induction motors__________?
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Answer: D. interchanging two supply phases for quick stopping
Explanation
Plugging temporarily reverses the stator rotating magnetic field direction relative to the rotor. Interchanging any two supply phases alters the phase sequence and creates an immediate braking torque. This rapid reversal brings the motor shaft to a swift stop during emergency shutdown procedures. Plugging is a dynamic braking technique that relies on electrical phase reversal for quick stopping. During plugging, the motor draws extremely high currents and generates severe internal mechanical stress. Braking contactors must disconnect the supply instantly as the motor reaches zero speed to prevent reversal.
Industrial machine tools and industrial hoists utilize plugging for rapid emergency braking operations. Operators must ensure mechanical components can handle the severe deceleration forces caused by plugging. Alternative braking methods like DC injection are often preferred to reduce thermal stress on windings. Option a describes direct on line starting rather than an emergency electrical braking method. Option b describes cogging caused by spatial harmonics rather than an intentional braking procedure. Option c describes overloading the motor mechanically rather than performing phase reversal.
- Subject
- Engineering
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- Electrical Engineering
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- —
- Difficulty
- medium
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