The PWM control of DC motor varies
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
Ward-Leonard system of system of speed control is not recommended for constant speed operation.
Mark the wrong option. Which of the following cause and effect behaviour in speed control is correct when field resistance is increased.
When field resistance is increased, emf actually decreases, not increases due to fall in flux.
At a very low speed, increase in field resistance will
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.
Small DC motors have best speed control by
For the small dc motors it is difficult to vary the speed using their field control.
To implement armature voltage control, it must be ensured that
It must be separately excited mahcine to implement the armature voltage control.
Armature voltage control works for speeds _____ base speed and field resistance control works well for speed _____ base speed.
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 speed for a shunt motor
The torque limit of the shunt motor remains constant till the base speed.
A laboratory group was working with a set of 3-hp shunt DC motor. But there was a mistake that it was fused with a 0.3A fuse instead 3A fuse. Then it was started
Due to the wrong usage of the fuse wire, it could not sustain the current and in few seconds it was blown off.
Run-away for large DC machine is avoided by using
The runaway in large machine is avoided by using compensating winding.