BEE experiment for Practical Notebook

Question

TOPIC 

To perform open circuit and short circuit test on a single phase transformer and calculate the efficiency. 

Write a procedure for the above experiment and draw observation table, circuit diagaram for the experiment. Also write theoretical and practical calculations if any. 

Answer 1

CIRCUIT DIAGRAM: 

OPEN CIRCUIT:

PROCEDURE: 

Open circuit test: 

1. Connections are made as per the circuit diagram. 

2. Ensure that variac is set to zero output voltage position before starting the experiment. 

3. Switch ON the supply. Now apply the rated voltage to the Primary winding by using Variac. 

4. The readings of the Voltmeter, ammeter and wattmeter are noted down in Tabular form. 

5. Then Variac is set to zero output position and switch OFF the supply.

 6. Calculate R_o and X_o from the readings. 

Short Circuit Test: 

1. Connections are made as per the circuit diagram. 

2. Ensure that variac is set to zero output voltage position before starting the experiment. 

3. Switch ON the supply. Now apply the rated Current to the Primary winding by using Variac. 

4. The readings of the Voltmeter, ammeter and wattmeter are noted down in Tabular form. 

5. Then Variac is set to zero output position and switch OFF the supply. 

6. Calculate R_o1 and X_o1 from the readings.

OBSERVATIONS: 

S.NO	Voc (Volts)	Ioc (Amps)	Woc(watts)
1

OPEN CIRCUIT TEST:

S.NO	Vsc (Volts)	Isc (Amps)	Wsc(watts)
1

MODEL CALCULATIONS: 

Find the equivalent circuit parameters R₀, X₀, R₀₁, R₀₂, X₀₁ and X₀₂ from the O. C. and S. C. test results and draw the equivalent circuit referred to L. V. side as well as H. V. side.

Let the transformer be the step-down transformer

Calculations to find efficiency and

regulation For example at 1/2 full load 

Cupper losses = W_sc x (1/2)² watts, where W_SC = full – load cupper 

losses Constant losses = W₀ watts 

Output = 1/2 KVA x cos \(\phi\) [cos \(\phi\) may be assumed] 

Input = output + Cu. Loss + constant loss

Efficiency at different loads and P.f’s

\(cos\,\phi = 0.8\)

Regulation: From open circuit and Short circuit test

‘+’ for lagging power factors 

- For leading power factor