Transformer MCQs Part 25

Transformer MCQs Part 25

For large-sized transformers, the cores are built up to nearly circular cross-section, this is done in order to reduce

For large-sized transformers, the cores are built up to nearly circular cross-section, this is done in order to reduce:

1. Iron losses
2. Copper losses
3. Eddy current losses
4. Leakage reactance

Correct answer: 2. Copper losses

Explanation: In case of large sized transformers the cores are build up to the nearly circular cross section in order to reduce the copper losses.

See complete List of Transformer MCQs here.

Laminating transformer core results in decreased

Laminating transformer core results in decreased:

1. Hysteresis loss
2. Leakage reactance
3. Eddy current losses
4. Copper losses

Correct answer: 3. Eddy current losses

A 10 V source of internal resistance 5 Ω is connected to load of 5 Ω through a transformer. For maximum power transformer, the turns ratio of transformer should be

A 10 V source of internal resistance 5 Ω is connected to load of 5 Ω through a transformer. For maximum power transformer, the turns ratio of transformer should be:

1. 1:1
2. 1:2
3. 2:2
4. 1:4

Correct answer: 1. 1:1

Zp/Zs = (N1/N2)^2

(N1/N2)^2 = Zp/Zs

(N1/N2)^2 = 5/5

(N1/N2)^2 = 1:1

The load on transformer is 3 ∠0° Ω or 3 ∠20° Ω. The efficiency of transformer will be

The load on transformer is 3 ∠0° Ω or 3 ∠20° Ω. The efficiency of transformer will be:

1. Greater for 3 ∠0° Ω
2. Greater for 3 ∠20° Ω
3. Same of both
4. None of above

Correct answer: 1. Greater for 3 ∠0° Ω

Explanation: For both loads, the copper and core losses will be same. However, the output power for 3 ∠0° Ω will be greater.

The secondary of PT is generally designed for

The secondary of PT is generally designed for:

1. 12 V
2. 24 V
3. 120 V
4. 220 V

Correct answer: 3. 120 V

Explanation: When measuring voltage levels of 480 V or less, self-contained meter can be used, provided that full-load current stays less than 600 A. However, if the voltage level exceeds a voltage level, a transformer rated meter is employed. A transformer used with meter is termed as instrument transformer.

Potential transformers are commonly referred to as “PT” units in the electrical power industry. It should be noted that the term “voltage transformer” and its associated abbreviation VT is becoming popular as a replacement for “potential transformer” and PT.

When driving a voltmeter – which is essentially an open-circuit (very high resistance) – the PT behaves as a voltage source to the receiving instrument, sending a voltage signal to that instrument proportionately representing the power system’s voltage. Continue Reading complete article here.