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It is desired to measure parameters of 230 V 115 V, 2 kVA, single-phase transformer. The following wattmeters are available in a laboratory:
W1 : 250V, 10 A, Low Power Factor
W2 : 250 V, 5 A Low Power Factor
W3 : 150 V, 10 A, High Power Factor
W4 : 150 V, 5 A, High Power Factor
The wattmeters used in open circuit test and short circuit test of the transformer will respectively be
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- W1 and W2
- W2 and W4
- W1 and W4
- W2 and W3
Correct Option: D
Open Circuit Test.
On L.V. side, rated voltage applied = 115 V
On L.V. side, current = 2 to 10% of rated current
| = | × | = 0.869 A | ||
| 100 | 115 |
A Since power consumed is less, so low power factor is used.
From available wattmeter,
W2 : 250 V, 5A. LPF used
Short Circuit Test
On H.V. side, rated current applied
| = | = 8.69A | |
| 230 |
A and, applied voltage = 5 to 15% of rated Voltage.
| = | × 230 = 23V | |
| 100 |
Hight power is consumed, so H.P.F used. From available wattmeter, W3: 150 V, 10A. HDF
Hence answer is W2 and W3.
