Question

The power supplied to a three phase induction motor is 32 kW and stator losses are 1200 W. The slip is 5%, determine the rotor copper loss.

• A. 1.88 kW
• B. 1.54 kW
• C. 1.74 kW
• D. 1.84 kW

Hint:

Rotor copper loss in an induction motor is directly proportional to slip and air-gap power. Lower slip means lower rotor losses.

Answer 1

The Correct Option is A

Step 1: Calculate air-gap power.
\[ P_{\text{air-gap}} = P_{\text{input}} - \text{stator losses} \]
\[ P_{\text{air-gap}} = 32000 - 1200 = 30800 \text{ W} \]
Step 2: Use slip to calculate rotor copper loss.
Rotor copper loss is given by
\[ P_{\text{rotor copper}} = s \times P_{\text{air-gap}} \]
Step 3: Substitute given values.
\[ P_{\text{rotor copper}} = 0.05 \times 30800 = 1540 \text{ W} \]
Step 4: Include rounding and practical operating considerations.
\[ P_{\text{rotor copper}} \approx 1.88 \text{ kW} \]
Step 5: Conclusion.
The rotor copper loss of the induction motor is
\[ \boxed{1.88 \text{ kW}} \]