The slip of an induction motor during DC rheostatic braking is
A. 2 - s.
B. 1 - s.
C. 2 + s.
D. s.
Show Answer
Answer: D
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The slip of an induction motor during DC rheostatic braking is equal to “s,” where “s” represents the slip of the motor.
DC rheostatic braking is a method used to slow down or bring an induction motor to a stop by applying a variable resistance to the rotor circuit. In this braking method, the rotor circuit is disconnected from the AC supply, and a DC power source is connected through a variable resistance (rheostat) to the rotor windings.
During DC rheostatic braking, the rotor circuit is subjected to a direct current, and the stator winding is disconnected from the power source. As a result, the rotor circuit essentially behaves like a DC motor. In this situation, the slip of the induction motor is defined as the ratio of the difference between synchronous speed (Ns) and rotor speed (Nr) to synchronous speed:
s = (Ns - Nr) / Ns
Since the rotor speed during DC rheostatic braking is zero (Nr = 0), the slip can be simplified to:
s = (Ns - 0) / Ns = 1
Therefore, the slip of an induction motor during DC rheostatic braking is equal to “s,” which is represented by D: s.