The power input to a 3 - φ induction motor is 60 kW and stator loss is 1 kW the rotor cu loss per phase is
A. slip X 50 / 3.
B. slip X 59 / 3.
C. slip X 69 / 3.
D. 1.
Answer: B
Share your understanding of this question with the correct explanation.
The answer is B. slip x 59 / 3.
The power input to the motor is 60 kW. The stator loss is 1 kW. This means that the rotor loss is 60 kW - 1 kW = 59 kW.
The rotor loss is divided equally between the three phases. This means that the rotor loss per phase is 59 kW / 3 = 19.67 kW.
The slip is the difference between the synchronous speed and the rotor speed. The synchronous speed is the speed at which the motor would run if there were no load on it. The rotor speed is the speed at which the motor is actually running.
The slip is calculated by dividing the rotor speed by the synchronous speed. In this case, the slip is 0.03.
The rotor copper loss is proportional to the square of the slip. This means that the rotor copper loss is 0.03² x 19.67 kW = 5.9 kW.
Therefore, the rotor copper loss per phase is 5.9 kW / 3 = 1.967 kW.
Here is the calculation in detail:
Power input to motor = 60 kW
Stator loss = 1 kW
Rotor loss = 60 kW - 1 kW = 59 kW
Rotor loss per phase = 59 kW / 3 = 19.67 kW
Slip = rotor speed / synchronous speed = 0.03
Rotor copper loss = slip² x rotor loss per phase = 0.03² x 19.67 kW = 5.9 kW
Rotor copper loss per phase = 5.9 kW / 3 = 1.967 kW`