Determine the rotor input and induction torque in a 400 V, 50 Hz, 4-pole, Y-connected induction motor operating at 2% slip with 240W power being lost in it’s rotor winding.

Determine the  rotor input and induction torque in a 400 V, 50 Hz, 4-pole, Y-connected induction motor operating at 2% slip with 240W power being lost in it’s rotor winding.

Solution:

Here,

V_L = 400v, f= 50Hz, P = 4, s = 2% = 0.02,

Rotor Cu Loss, P_cr = 240W

N_S = 120f/P = 120*50/4 = 1500rpm

Nr = N_S (1-s) = 1500(1-0.02) = 1470rpm

We know, P_cr / P_m= s /(1-s).

P_m = P_cr (1-s)/s = 240(1-0.02)/0.02 = 11760Watt

Induction torque, τ_ind = 9.55*P_m/N_r = 9.55*11760/1470 = 76.4Nm (Ans)

 Rotor input, P₂ = P_cr /s = 11760/0.02 = 12000Watt. (Ans)

 

EEE Job Math-5

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