In an induction motor the slip will be negative whena)stator magnetic ...
Negative slip indicates that the motor is running above synchronous speed. This can happen only when it is driven by a prime mover. This motor becomes an induction generator. For it to generate, it must be connected to a power supply, from where it can draw magnetising current.
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In an induction motor the slip will be negative whena)stator magnetic ...
Explanation:
In an induction motor, the slip refers to the difference between the synchronous speed of the rotating magnetic field in the stator and the actual speed of the rotor. It is expressed as a percentage of the synchronous speed.
The synchronous speed is determined by the frequency of the power supply and the number of poles in the motor. It represents the speed at which the rotating magnetic field in the stator would rotate if there were no slip.
Slip Calculation:
The slip is calculated using the formula:
Slip = (Ns - Nr) / Ns * 100
Where:
Ns = synchronous speed
Nr = rotor speed
Slip and Direction of Rotation:
When the rotor of an induction motor rotates at a speed less than the synchronous speed and in the direction of rotation of the stator field, the slip is positive. This means that the rotor is lagging behind the rotating magnetic field in the stator.
On the other hand, when the rotor rotates at a speed more than the synchronous speed and in the direction of rotation of the stator field, the slip is negative. This means that the rotor is running faster than the rotating magnetic field in the stator.
Explanation of Correct Answer:
In the given options, option 'C' states that the slip will be negative when the rotor rotates at a speed more than the synchronous speed and in the direction of rotation of the stator field. This is the correct answer.
When the slip is negative, it indicates that the rotor is running faster than the rotating magnetic field in the stator. This situation is not possible in an induction motor under normal operating conditions. It would require an external force or some abnormal condition to cause the rotor to run faster than the synchronous speed.
Therefore, in a properly functioning induction motor, the slip is always positive or zero. A negative slip is not possible, which is why option 'C' is the correct answer.
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