301. The core of the transformer is made of good quality material like CRGO steel to minimize

- Eddy current loss
- Full load copper loss
- Hysteresis loss
- No-load coper loss

302. For a minimum weight of a transformer, the weight of iron should be

- Equal to weight of copper
- Less than the weight of copper
- Greater than the weight of copper
- Zero

303. The voltage transformation ratio of a transformer is equal to the ratio of

- Primary turns to secondary turns
- Secondary current to primary current
- Secondary induced e.m.f to primary induced e.m.f.
- Secondary terminal voltage to primary applied voltage

304. Which of the following is the most likely source of harmonics in a transformer?

- Poor insulation
- Overload
- Loose connections
- Core saturation

305. When a transformer is run at its rated voltage but at a reduced frequency, its

- Flux density remains unaffected
- Iron losses are reduced
- Core flux density is reduced
- Core flux density is increased

306. A transformer can have zero voltage regulation at a

- Laggingpower factor
- Zero power factor
- Unity power factor
- Leading power factor

307. Which of the following is not a routine test on transformers?

- Core insulation voltage test
- Impedance voltage test
- Polarity test
- Radio interference test

308. The power transformer is a constant

- Voltage device
- Current device
- Power device
- Main flux device

309. The Power transformers are designed to have maximum efficiency at

- No-load
- 70% full load
- 50% full load
- Nearly full load

310. No-load on a transformer is carried out to determine the

- Copper loss
- Magnetizing current
- Magnetizing current and loss
- Efficiency of the transformer

311. A 50 Hz transformer having equally hysteresis and eddy current losses at the rated excitation is operated at 45 Hz at 90 % of its rated voltage. Compared to the rated operating point, the core losses under this condition

- Reduced by 10 %
- Reduced by 19 %
- Reduced by 14.5 %
- Remain unchanged

312. A 10 KVA, 400 V/200V single-phase transformer with 10% impedance draws a steady short circuit line current of

- 50 A
- 150 A
- 250 A
- 350 A

313. A current transformer has double turn primary and a 100 turn secondary winding. The secondary draws current of 6 Amp and magnetizing ampere-turns is 60 Amp. What is the actual transformation ratio?

- 100.5
- 101
- 50.24
- 25.12

314. Transformer utilization factor of TUF = K signifies

- That transformer for rectifier should be 1/K times larger than that for ac source
- That transformer for rectifier should be K-1 times larger than that for ac source
- That transformer for rectifier should be 1-K times larger than that for ac source
- That transformer for rectifier should be K time larger than that for ac source

315. The parallel operation of 2 transformers with which of the following vector groups is possible?

- Yd11 and Yd1
- Yd11 and Yd6
- Dd1 and Yd1
- Dy1 andYy1

316. The exciting current in a single-phase transformer consists of

- Fundamental and odd harmonics
- Odd harmonics
- Even harmonics
- Fundamental component current

317. A transformer is operating at the no-load condition and draws an exciting current (I_{0}) of 5 A when the primary side is connected to a 120 V, 60 Hz source. By doing a wattmeter test, the iron losses are equal to 180 Watts. The reactive power absorbed by the core is

- 600 VAR
- 572 VAR
- 180 VAR
- 360 VAR

318. A transformer rated 250 kVA, 4.16 kV/480 V, 60 Hz has an impedance of 5.1%. calculate the total impedance of the transformer referred to the primary

- 69 Ω
- 0.92 Ω
- 3.52 Ω
- 0.51 Ω

319. Which test is used to determine the magnetizing impedance of a transformer?

- Short-circuit test
- Impulse test
- Load test
- Open-circuit test

320. Find the transformer tap ratios when the receiving end voltage (V_{r}) is equal to the sending end voltage (V_{s}). The high-voltage line operates at 220 kV and transmits 80 MW at 0.8 power factor and the impedance of the line is (40+j140) Ω. (Assume that t_{s}t_{r }= 1)

- 0.6
- 0.7
- 0.9
- 0.8