# An open circuit test is conducted on a 1100/110 V, 50 Hz single-phase transformer with instruments connected on the low voltage side of the transformer.

An open circuit test is conducted on a 1100/110 V, 50 Hz single-phase transformer with instruments connected on the low voltage side of the transformer. The voltmeter reads 110 V. The ammeter reads 2 A. The wattmeter reading is 65 W. The approximate core-loss resistance and magnetizing reactance, referred to as the low voltage side, are respectively.

### Right Answer is: 186.15 Ω, 57. 575 Ω

#### SOLUTION

Given

Vo = 110 V

Io = 2 A

Po = 65 W

Power can be expressed as

Po = VoIo Cosφ

Cosφ = Po/VoIo

Cosφ = 65/110 × 2

Cosφ = 0.295

sinφ = 0.955

The core loss component of the current can be expressed as

Iw = IoCosφ

Iw = 2 × 0.295

Iw = 0.6W

Magnetizing component of current can be expressed as

Im = Iosinφ

Im = 2 × 0.955

Im = 1.9 A

Cores loss Resistance

Ro = V/Iw = 110/0.6

Ro = 186.44 Ω

Magnetizing reactance

Xm = Vo/Im = 110/1.9

Xm =57.89 Ω

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