21. What is the difference between MCB & MCCB, Where it can be used?

MCB is miniature circuit breaker which is thermal operated and use for short circuit protection in small current rating circuit. MCCB moulded case circuit breaker and is thermal operated for over load current and magnetic operation for instant trip in short circuit condition.under voltage and under frequency may be inbuilt. Normally it is used where normal current is more than 100A.

22. Let an electric train is driven by a dc series motor that faces a constant power load. It is running at rated speed and rated voltage. In order to bring down the speed to 0.25 p.u. the supply voltage has to be brought down to ......

0.5p.u.

23. Can we improve power factor by connecting static capacitors in parallel with the load operating at lagging power factor?

Yes

24. Explain Demand Factor?

It is defined as the ratio of actual maximum demand made by the load to the rating of the connected load.

25. Explain the term real power in ac circuits?

It is the product of voltage, current and power factor i.e. P = V I cos j and basic unit of real power is watt. i.e. Expressed as W or kW.

26. Transformer losses have two sources..........and magnetic loss

copper loss

27. Name two types of earthing you are familiar?

Equipment earthing and system earthing

30. Where should the lighting arrestor be placed in distribution lines?

Near distribution transformers and out going feeders of 11kv and incomming feeder of 33kv and near power transformers in sub-stations.

31. Is it possible to start up a 36w or 40w 220V AC/DC tube light without the help of Coil or Choke?

It is not possible without the help of electric coil or choke. Because, the coil or choke ionize the particles in the tube light. In normal voltage it is not possible to ionize the particle.

32. Why the capacitor works doesnâ€™t work on DC?

The capacitor normally gives an infinite resistance to DC component. But, it allows AC power component to pass through the devices. These resistances of the capacitor blocks work of DC component.

33. In the ...... Stability there is a large duration phenomenon with small disturbance

Static

34. .......Stability refers to artificial stability

Dynamic

35. A big amount of Copper loss is a disadvantages of low power factor - Agree

Yes

The ratio of Average load and the Maximum demand in a given period of time in a power plant is known as load factor.

Q.1- 11  Q.12 - 20  Q. 21 - 36 Q. 37 - 50  Q. 51 - 65   Q. 66 - 78   Q. 79 - 87   Q. 88 - 100

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