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

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what happens if the resistance in series with the shunt field of a DC motor is increased in value

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….

Calculate the synchronous speed of a 10-pole three-phase machine connected to a 50 Hz supply.

1. The generator characteristic shown in Figure 9.28 is for a   (a) shunt machine (b) series machine (c) differentially compounded machine (d) cumulatively compounded machine 2.The speed of a….

Draw a circuit diagram showing a single-phase wattmeter measuring the power in a single-phase 6.6 kV 500Acircuit by means of current and voltage transformer

1.The resistance material used for meter shunts is chosen for its very low value of   temperature coefficient of resistance. Why is this so? 2.State briefly with the aid of….