# 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

V_{o} = 110 V

I_{o} = 2 A

P_{o} = 65 W

Power can be expressed as

P_{o} = V_{o}I_{o} Cosφ

Cosφ = P_{o}/V_{o}I_{o}

Cosφ = 65/110 × 2

**Cosφ = 0.295**

∴ **sinφ = 0.955**

The core loss component of the current can be expressed as

I_{w} = I_{o}Cosφ

I_{w} = 2 × 0.295

**I _{w} = 0.6W**

Magnetizing component of current can be expressed as

I_{m} = I_{o}sinφ

I_{m} = 2 × 0.955

I_{m} = 1.9 A

Cores loss Resistance

R_{o} = V/I_{w} = 110/0.6

**R _{o} = 186.44 Ω**

Magnetizing reactance

X_{m} = Vo/I_{m} = 110/1.9

**X _{m} =57.89**

**Ω**