1. Sparking at the trailing edges of the brushes in a DC machine is usually prevented by fitting (a) copper gauze brushes (b) a compensating winding (c) a compound….
Sketch the load characteristics, terminal voltage/load current, of the following types of DC generator
1. (a) Sketch the load characteristics, terminal voltage/load current, of the following types of DC generator: (i) series-connected, (ii) shunt-connected and (iii) compound-connected.
(b) State one purpose for which each is used.
2. Sketch the current/torque and speed/torque characteristics of series, shunt and both types of compounded DC motors. Suggest a suitable use for each type of machine.
3.(a) What is meant by the back EMF of a DC motor?
(b) A 250 V shunt motor has field resistance of 125 _ and armature resistance of 0.25 _. (i) Find the back EMF when the motor is running and taking