A 4 pole d.c motor takes a 50 A armature current. The armature has lap-connected 480 conductors. The flux per pole is 20 mWb. Calculate the gross torque developed by the armature of the motor.

A 4 pole d.c motor takes a 50 A armature current. The armature has lap-connected 480 conductors. The flux per pole is 20 mWb. Calculate the gross torque developed by the armature of the motor.

Right Answer is: 76.32 N-m

SOLUTION

Number of Poles P = 4

Number of parallel Path A = 4  (In Lap wound the number of brush required by this winding is always equal to the number of poles.)

Total number of armature conductor Z = 480

Flux per Pole Φ = 20 mWb = 20 x 10-3 Wb,

Armature current Ia = 50 A

$\begin{array}{l}{T_a} = 0.159\Phi {I_a}\dfrac{{PZ}}{A}\\\\ = 0.159 \times 20 \times {10^{ – 3}} \times 50\dfrac{{4 \times 480}}{4}\\\\{T_a} = 76.32{\text{ N – m}}\end{array}$

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