To determine the efficiency and losses of a given transformer accurately under full load condition.

Aim

To determine the efficiency and losses of a given transformer accurately under full load condition.

Apparatus Required:

Transformer Specifications:

Two identical 1- ɸ Transformers

Transformer Rating :(in KVA) ____________

Winding Details:

LV (in Volts): ________________________

LV side current:______________________

HV (in Volts): ________________________

HV side Current:______________________

Type(Shell/Core):______________________

1 - ɸ Auto transformer Specifications:

Input Voltage (in Volts):_________________

Output Voltage (in Volts): _______________

frequency (in Hz):____________________

Current rating (in Amp):_____________

Circuit Diagram:

Procedure:-

Open circuit test:

1. Make the connections as per the circuit diagram.
2. The secondary winding terminals of the two transformers are connected in series with polarities in phase opposition which can checked by means of a voltmeter.
3. Before starting the experiment, check the variacs are in minimum output voltage position.
4. Increase the variac slowly, and apply rated voltage to the primary windings of 1-ɸ transformers and check the voltmeter reading connected across the secondary terminals.
5. If the voltmeter reading is Zero, continue with step 9.
6. Now close the DPST-2 switch and vary the variac-2 slowly till rated current flows in the two series-connected secondaries.
7. Note down the readings of V₁,V₂, I₁, I₂, W₁, and W₂ and enter them in a tabular column.
8. W₁ = 2P_C, W₂= 2P_SC. Losses of each transformer = (W₁+W₂)/2 Now the Variacs are brought to zero voltage position and open DPST switches.

Observation:

Model Calculations:

Losses in each transformer=(W_i+W_c)/2

% η of each transformer = (VI₁)/( VI₁ +W_i/2+W₁/2)*100

Precautions:

1. Connections must be made tight.
2. Before making or breaking the circuit, supply must be switched off.

Result:Efficiency of given Two transformers are found using Sumpner’s test.

Precautions:

1. What for this test is really intended?
2. Why to conduct the test on identical transformers?
3. What happens if the rated values of voltage and frequency of supply vary?
4. What are the advantages and disadvantages of this test?
5. Can you perform this test on 3 – Φ star/ delta transformers?
6. What is all-day efficiency?

---

---