Power Generation MCQs Part 30

Power Generation MCQs Part 30

An alternator alters _________ to __________

An alternator alters _________ to __________:

1. Mechanical energy, Electrical Energy
2. Electrical energy, Mechanical Energy
3. Electrical energy, Chemical energy
4. Heat energy, Electrical energy

Correct answer: 1. Mechanical energy, Electrical energy

Mechanical energy is supplied to a DC generator at rate of 90 J/s

Mechanical energy is supplied to a DC generator at rate of 90 J/s. The generator delivers 40 at 90 V. The efficiency of generator is:

1. 33784
2. 32784
3. 31784
4. 30784

Correct answer: 3. 31784

Solution:

Mass of water available = 90 * 1000 = 90000 kg/sec

————

Head = 40 m

Work done/sec = W*H = 90000 * 40 = 35316 * 10³ W = 35316 kW

This is gross plant capacity.

———————

Firm capacity = Plant efficiency * Gross plant capacity

Firm capacity = 0.9 * 35316 = 31784 kW

Certain power station has an average demand of 15 MW

Certain power station has an average demand of 15 MW. If plant capacity factor is 50% and load factor is 60%. The reserve capacity of plant is:

1. 2 MW
2. 5 MW
3. 15 MW
4. 25 MW

Correct answer: 2. 5 MW

Solution:

From formula of Plant capacity factor

Plant capacity factor = Average demand/Plant capacity

Plant capacity = Average demand/Plant capacity factor = 15/0.5 = 30 MW

——————-

Maximum demand = Average demand/Load factor = 15/0.6 = 25 MW

——————-

Reserve capacity of plant = Plant capacity – Max.demand = 30 – 25 = 5 MW

A diesel power station has fuel consumption per day = 2000 kg

A diesel power station has fuel consumption per day = 2000 kg. The units generated per day are 8000 kWh. The specific fuel consumption is:

1. 0.17%
2. 0.21%
3. 0.25%
4. 0.29%

Correct answer: 3. 0.25%

Solution:

Specific fuel consumption = 2000/8000 = 0.25