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If the stator voltage and frequency of an induction motor are reduced proportionately,its
- a)locked rotor current is reduced
- b)torque developed is increased
- c)magnetising current is decreased
- d)both (a) & (b)
Correct answer is option 'D'. Can you explain this answer?
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If the stator voltage and frequency of an induction motor are reduced ...
**Explanation:**
When the stator voltage and frequency of an induction motor are reduced proportionately, the following changes occur:
**1. Locked Rotor Current is Reduced:**
- When the stator voltage and frequency are reduced proportionately, the reactance of the motor increases.
- As a result, the impedance of the motor increases and limits the flow of current through the motor.
- This reduction in current flow leads to a decrease in the locked rotor current of the motor.
- Therefore, option (a) is correct.
**2. Torque Developed is Increased:**
- The torque developed by an induction motor is directly proportional to the square of the stator voltage and inversely proportional to the stator frequency.
- When both the stator voltage and frequency are reduced proportionately, the torque developed by the motor increases.
- This is because the reduction in voltage is compensated by the reduction in frequency, resulting in a higher torque output.
- Therefore, option (b) is correct.
**3. Magnetising Current is Decreased:**
- The magnetising current of an induction motor is primarily dependent on the stator voltage.
- When the stator voltage is reduced proportionately, the magnetising current also decreases.
- This is because the reduced voltage results in a lower magnetic flux in the motor, leading to a decrease in the magnetising current.
- Therefore, option (c) is correct.
Hence, when the stator voltage and frequency of an induction motor are reduced proportionately, the locked rotor current is reduced, the torque developed is increased, and the magnetising current is decreased. Therefore, the correct answer is option (d) - both (a) and (b).
When the stator voltage and frequency of an induction motor are reduced proportionately, the following changes occur:
**1. Locked Rotor Current is Reduced:**
- When the stator voltage and frequency are reduced proportionately, the reactance of the motor increases.
- As a result, the impedance of the motor increases and limits the flow of current through the motor.
- This reduction in current flow leads to a decrease in the locked rotor current of the motor.
- Therefore, option (a) is correct.
**2. Torque Developed is Increased:**
- The torque developed by an induction motor is directly proportional to the square of the stator voltage and inversely proportional to the stator frequency.
- When both the stator voltage and frequency are reduced proportionately, the torque developed by the motor increases.
- This is because the reduction in voltage is compensated by the reduction in frequency, resulting in a higher torque output.
- Therefore, option (b) is correct.
**3. Magnetising Current is Decreased:**
- The magnetising current of an induction motor is primarily dependent on the stator voltage.
- When the stator voltage is reduced proportionately, the magnetising current also decreases.
- This is because the reduced voltage results in a lower magnetic flux in the motor, leading to a decrease in the magnetising current.
- Therefore, option (c) is correct.
Hence, when the stator voltage and frequency of an induction motor are reduced proportionately, the locked rotor current is reduced, the torque developed is increased, and the magnetising current is decreased. Therefore, the correct answer is option (d) - both (a) and (b).
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If the stator voltage and frequency of an induction motor are reduced proportionately,itsa)locked rotor current is reducedb)torque developed is increasedc)magnetising current is decreasedd)both (a) (b)Correct answer is option 'D'. Can you explain this answer?
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