# Efficiency in Single-Phase Transformer - MCQs with Answers

## Efficiency in Single-Phase Transformer - MCQs with Answers

Q1. For maximum efficiency in a transformer

a. Core losses = 2 * copper losses
b. Core losses = copper losses / 2
c. Core losses = copper losses
d. Core losses = copper losses ∧ 2

ANSWER: c. Core losses = copper losses

Q2. If the power factor of a transformer is increases, then its efficiency will

a. Increases
b. Decreases
c. Remains constant
d. Not related to each other

Q3. When a transformer is supplied by full load at 0.8 p.f. lagging its copper losses is given by Pcu. if it is supplied by half load then copper losses will be

a. Pcu.
b. 2Pcu.
c. Pcu / 2.
d. Pcu / 4.

Q4. A 600 kVA transformer has iron losses of 400 kW and copper losses of 500 kW. Its kVA rating for maximum efficiency is given by

a. 537 kVA
b. 548 kVA
c. 555 kVA
d. 585 kVA

Q5. In a 20 kVA, 2200 / 220 volts transformer iron and copper losses are 300 and 400 watts respectively. Its efficiency at half load and unity power factor is

a. 95.11%
b. 96.15%
c. 97.77%
d. 98%

Q6. A 500 kVA single phase transformer has 90% efficiency at both half load and full load at unity power factor. Then iron losses will be

a. 12.55 KW
b. 13.55 kW
c. 16.55 kW
d. 18.55 Kw

#### Discussion

• RE: Efficiency in Single-Phase Transformer - MCQs with Answers -Malleshwari ponnam (06/11/20)
• My answer is 18.55...because we know the output Nd the efficiency by this we can find the input
Like this
90=500/90...._Eq1
By solving above equation we get
• RE: Efficiency in Single-Phase Transformer - MCQs with Answers -Malleshwari ponnam (06/11/20)
• My answer is 18.85...because we know the output Nd the efficiency by this we can find the input
Like this
90=500/90...._Eq1
By solving above equation we get