Purchase Solution

# A 20 kW, 500 V d.c. shunt wound motor draws a current of 45 A when running at full load

Not what you're looking for?

6. (i) A 20 kW, 500 V d.c. shunt wound motor draws a current of 45 A when running at full load with a speed of 600 rev min-1. On no load, the current drawn from the supply is 5 A. If the armature resistance is 0.3 ohms and the shunt field resistance is 220 ohms, calculate the armature current, speed and efficiency of the motor when the torque falls to half of its full load value, assuming that the flux per pole does not change.

(Hint: don't forget that all armature current is supplying torque. One must decide at some points what is the armature current producing
torque and at others, to determine generator emfs, the total armature current).

(ii) State what you would expect to happen to the speed if a resistance is inserted into the field circuit.

(iii) If a resistance of 50 ??is inserted in series with the shunt field, calculate the armature current required to maintain half full-load
torque. Calculate also the speed of the motor when supplying this torque.

##### Solution Summary

The expert examines shunt wound motor drawing a current of 45A running at full load. What you would expect to happen to the speed if a resistance is inserted into the field circuit is determined.

##### The Moon

Test your knowledge of moon phases and movement.

##### Introduction to Nanotechnology/Nanomaterials

This quiz is for any area of science. Test yourself to see what knowledge of nanotechnology you have. This content will also make you familiar with basic concepts of nanotechnology.