Calculate the kVAr rating of a capacitor to correct the motor power factor to 0.99 lagging.

1. An electrical installation is to be power-factor corrected. One large motor has a maximum rating of 125 kW at 0.78 power factor lagging. Calculate the kVAr rating of a capacitor to correct the motor power factor to 0.99 lagging. 2. The electrical supply company rules which decide how much we pay for our electrical energy is called the

 

(a) account (b) tariff (c) charge (d) bill

3. The demand for electrical energy is almost always much lower during the early hours of the morning than during the day. This is because

(a) of the way the off-peak tariffs are arranged

(b) power stations are shut down at night

(c) electricity costs are very much higher in the early hours of the morning

(d) most consumers are asleep and not using electricity

 

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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….

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….