A 480 V, 50 Hz, 4 pole three-phase induction motor rated at 20 kW has a rated power factor of 0.78 at a rated speed of 1440 rpm. The mechanical loss at this rated the condition is given as 0.9 kW. The total copper losses and core losses are given as 1.4 kW and 0.5 kW.

(a) Calculate the rated rotor slip.

(b) Calculate the total input real power and reactive power under rated conditions.

P= (kW)

Q = (kVAr)

(c) If the excitation voltage is increased from 13.8 kV to 15 kV, calculate the new real and reactive power delivered to the grid if the torque angle is found to remain at 8.15 ⁰