Question

The armature of a 4-pole dc shunt motor has a lap winding accommodated in 60 slots, each containing 20 conductors. If the useful flux per pole is 23 mWb and the armature current is 50 A, then the torque (in N-m) developed in motor is

• A. 219.63

Answer 1

The correct option is A 219.63
$\text{Torque developed in motor}=\frac{\text{Power developed in armature}}{\left(\frac{2\pi N}{60}\right)}$
$T=\frac{E_b.I_a\times 60}{2\pi N}$

$=\frac{\varphi ZNP}{60A}\times \frac{I_a\times 60}{2\pi N}\text{[P = A, since it is lap winding]}$

$T=\frac{\varphi Z{I}_a}{2\pi }=\frac{23\times {10}^{-3}\times 60\times 20\times 50}{2\pi }=219.63N-m$