Question

An ideal frictionless DC permanent magnet motor operating from a 24 V source has a no load speed of 240 radians/sec and an armature resistance of 0.2 Ohms. Compute the stall torque of the motor in Newton-meters.

Answer 1

12 N-m

Step-by-step explanation:

The dc motor is operating at 24 V that is its terminal voltage V =24 V

Armature resistance
`R_a` = 0.2 ohm

No load speed = 240 radian /sec

For motor we know that
`V=E_b+iR_a` as the motor is on no load so
`E_b=0` so
`i=(V)/(R_a)=(24)/(0.2)=120A`

Power developed in the motor
`P=Vi=120* 24=2880W`

Now we know that power = torque× angular speed

So
`2880=\tau * 240`

`\tau =(2880)/(240)=12N-m`