help5

Question

Answer 1

5.3)

The purpose of capacitor in a single phase capacitor motor:

Single phase induction motor is not the self starting so, to make it self start we can use capacitor.

Capacitor also provides high starting torque to run the motor.

The capacitor is used to make a single-phase motor rotate in one direction only by supplying a phase shift voltage to a starting winding on the motor.

Answer 2

5.5.1)

Feeder is defined as lines, which connect the distribution station and distributor.

Distributor is defined as a common bus bar, which connect the service main and feeder.

The most two types of feeders used in transmission system are,

1) Radial distribution system.

2) Primary Loop distribution system.

Answer 3

5.2)

Buchholz relay is a gas operated relay used for the protection for oil immersed transformer against all internal faults

A Buchholz relay is used to detect:

1) Loss of oil

2) Presence of gas generated by minor inter winding faults

3) Catastrophic insulation breakdown

Initially, a loss of oil initiates an alarm. If the oil loss continues, then the relay will initiate disconnection of the transformer. The presence of gas initiates an alarm. Catastrophic insulation breakdown initiates the disconnection of the transformer.

Answer 4

5.4)

Silica gel crystals are commonly used in the breather of a transformer.

Silica gel breathers provide an economic and efficient means of controlling the level of moisture entering the conservator tank during the breathing process.

Answer 5

(5.1)

Step 1:

A 230 V DC supply is connected across 300 in series to a unknown resistor R.

The Voltmeter connected across 300 resistor has internal resistance of 300 and reads 30 V.

Let be the unknown resistance.

Draw a circuit using above specifications.

Redraw the circuit replacing the voltmeter with its equivalent internal resistance.

Voltage in a parallel network is same.

Current through is

Since and are equal, current flowing through the voltmeter is 0.1 A.

Current in the series network is same, hence current flowing in the circuit is equal to the sum of the currents flowing in the parallel network.

Hence total current flowing in the circuit is .

Step 2:

Total resistance of the network is .

Calculate the equivalent resistance of the circuit.

and are parallel then .

Equivalent resistance is .

Substitute and in .

The value of unknown resistance .

Solution:

The value of unknown resistance .