The equivalent circuit of a single-phase induction motor is shown in the figure, where the parameters are R_{1}-R_{2}^{'}-X_{l_{2}}-X_{L_{2}}^{'}-12 Ω_{r}, X_{M}-240 Ω and s is the slip. \Lambda t no-load the motor speed can be approximated to be the synchronous speed. The no-load lagging power factor of the motor is (upto 3 decimal places).

GATE Electrical Engineering (EE) 2018 Solved Paper

Question : 46 of 65

Marks: +1, -0

The equivalent circuit of a single-phase induction motor is shown in the figure, where the parameters are

R_{1}-R_{2}^{'}-X_{l_{2}}-X_{L_{2}}^{'}-12 Ω_{r}, X_{M}-240 Ω

and s is the slip.

Λ t

no-load the motor speed can be approximated to be the synchronous speed. The no-load lagging power factor of the motor is (upto 3 decimal places).

Solution:

At synchronous speed s=0
So, the equivalent circuit will be

Z_{e q} \;\; =\;{(3+j 6)(j 120)}/{(3+j 126)}+[12+j 132]

\;\; =138.563 ∠ 83.9 Ω

Impedance angle will be p.f. angle

∴

No-load lagging p.f. of motor is

\cos (83.9)=0.106

lagging power factor

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