Test: Speed Control of DC Motors - Electrical Engineering (EE) MCQ

In PWM technique duty ratio is a linear function with respect to speed.

Ward-Leonard system of system of speed control is not recommended for constant speed operation.

When field resistance is increased, emf actually decreases, not increases due to fall in flux.

At low speed increase in armature current caused by decrease in emf, will not be enough to compensate for decrease in flux in induced torque equation.

 For the small dc motors it is difficult to vary the speed using their field control.

It must be separately excited mahcine to implement the armature voltage control.

For armature voltage control, armature current is increased so as to reduce speed below base speed. In field control flux is reduced so the speed would be above base speed.

The torque limit of the shunt motor remains constant till the base speed.

Due to the wrong usage of the fuse wire, it could not sustain the current and in few seconds it was blown off.

The runaway in large machine is avoided by using compensating winding.