THREE PHASE INDUCTION MOTOR
1. If the frequency of 3-phase supply to the stator of a 3-phase induction motor is increased, then synchronous speed 1. Increased ✓ 2. Decreased 3. Remain unchanged 4. None of the above Synchronous speed of the 3 phase induction motor is Ns = 120f/p From the above equation, it is clear that the synchronous speed is directly proportional to the applied frequency. I.e Ns ∝ f Hence by increasing the frequency, the synchronous speed of the 3 phase induction motor can be increased. 2. A 3 phase induction motor is essentially a 1. Constant speed motor ✓ 2. Variable speed motor 3. Very costly 4. Easily maintainable The induction motor is not a perfectly constant speed motor . At no load, the rotor lags behind the stator flux only a small amount since the only torque required is that needed to overcome small no-load losses. Hence it rotates at almost the...