The document describes a load test conducted on a single phase transformer. Key details include: 1) Readings of voltage, current, power, and efficiency were recorded from meters under no load and different load conditions up to 125% of rated primary current. 2) Calculations of regulation, power factor, and efficiency were done based on the recorded values. 3) The results showed the efficiency and voltage regulation values obtained from testing the transformer under different load conditions.

1. DEPT. OF ELECTRICAL & ELECTRONICS ENGINEERING
SRM INSTITUTE OF SCIENCE AND TECHNOLOGY, Kattankulathur – 603 203
Title of Experiment : LOAD TEST ON SINGLE PHASE
TRANSFORMER
Date of Experiment : 11-12-2020
Sl.
No.
Marks Split up Maximum marks
(50)
Marks obtained
1 Pre Lab questions 5
2 Preparation of observation 15
3 Execution of experiment 15
4 Calculation / Evaluation of Result 10
5 Post Lab questions 5
Total 50
Staff Signature
Name of the candidate : S D N V MANIKANTA SAI KUMAR
Register Number : RA2011003010815

2. PRE LAB QUESTIONS
1. Explain the working principle of transformer?
A transformer consists of two electrically isolated coils and operates on Faraday's
principal of “mutual induction”, in which an EMF is induced in the transformers
secondary coil by the magnetic flux generated by the voltages and currents flowing in
the primary coil winding.
2. What are the main parts of a transformer?
There are three basic parts of a transformer:-
1)an iron core which serves as a magnetic conductor,
2)a primary winding or coil of wire and.
3)a secondary winding or coil of wire.
3. What are the types of transformers?
There are three primary types of voltage transformers (VT): electromagnetiC
capacitor, and optical. The electromagnetic voltage transformer is a wire-wound
transformer. The capacitor voltage transformer uses a capacitance potential divider
and is used at higher voltages due to a lower cost than an electromagnetic VT.
4. What is the meaning of KVA rating of transformer?
In relation to transformers, the 'KVA(Kilovolt – Ampere) rating' of a transformer tells
you how much apparent power can flow through a transformer without exceeding a
temperature rise associated with the rating.
5. What is the necessity of the load test for a transformer?
The purpose of load test is to determine the parallel operation and calculate the
efficiency, thermal stability and dynamic stability of a transformer.

3. Experiment No.06
Date :11-12-2020 Load test on single phase transformer
Aim:
To conduct the load test on the given a single phase transformer for finding the
efficiency and its regulation.
Apparatus Required:
S.NO APPARATUS RANGE TYPE QUANTITY
1. Voltmeter (0-150)V
(0-300) V
MI
MI
1
1
2. Ammeter
(0-10)A
(0-20) A
MI
MI
1
1
3. Wattmeter 150V,20A
300V,10A
UPF
UPF
1
1
4. Auto transformer 240 V,
2.7 KVA,10A
1
Formula Used:
1.Percentage Regulation = (Vo2-V2) /Vo2*100
Where Vo2 = Secondary voltage on noload
Vo = Secondary voltage at a particular load
2.Power factor = Pout/V2*I2
Where Pout = Secondary wattmeter readings in Watts
V2 = Secondary voltage inVolts
I2 = Secondary current in Amp
3. Percentage efficiency = Pout/Pin*100
Where Pout = Secondary wattmeter readings in Watts
Pin = Primary wattmeter readings in Watts.

4. CIRCUIT DIAGRAM:
E-Circuit Simulation:-

5. Procedure
1.Connections are given as per the circuit diagram.
2.Verify whether the autotransformer is kept at zero voltage position.
3.By closing the DPST switch, 230V,1 ,50HZAC supply is given to
the transformer. 4.At no load, the readings from the meters are noted
down.
5.The load is applied to the transformer in steps upto 125% of the
rated value of the primary
Current by using rheostatic load..
6.The corresponding values from the meters are tabulated for different
loads.
7.Then the load is removed gradually, auto transformer is brought to
its minimum position and the supply is switched off.
8.From the recorded values, the regulation, power factor and
efficiency are calculated.
Model Graph:
% reg
Pout

6. TABULATION:
V02=115.05
S.
No
Prima
ry
Volta
ge
V1 (V)
Prima
ry
Curre
nt
I1 (A)
Primar
y
Wattm
eter
W1 (W)
Second
ary
Voltag
e
V2 (V)
Second
ary
Curren
t
I2 (A)
Second
ary
Wattm
eter
W2 (W)
Pow
er
Fact
or
Cos
%
Regulatio
n
%
%
1 230 0 0 115 0 0 0 0 0
2 230 1.1 253 114 2 228 1 0.8 90
3 230 1.3 299 111 2.5 277.5 1 3.4 92.8
4
5
6
230
230
230
1.8
2.3
2.5
414
529
575
110
109
108
3.4
4.3
4.4
374
468.7
475.2
1
1
1
4.3
5.2
6
90.3
88.6
82.6
Model Calculation:

9. Graphs:-
Result:-The load test on a single phase transformer is conducted and the values of efficiency
and voltage regulations are recorded.

10. POST LAB QUESTIONS
1. What will happen if a DC voltage is given to the transformer primary?
When a DC voltage is applied to the primary winding of a transformer, due to low
resistance, the winding acts as a short circuit across the terminals of the DC source that
lead to the flow of heavy current through the winding resulting in overheating of the
winding.
2. What are the losses in a transformer?
There are various types of losses in the transformer such as iron loss, copper loss,
hysteresis loss, eddy current loss, stray loss, and dielectric loss.
3. How can we minimize the core losses in a transformer?
Core losses majorly include Hysteresis loss and eddy current loss.
Eddy Current loss can be reduced by increasing the number of laminations. The
laminations provide small gaps between the plates. As it is easier for magnetic flux to
flow through iron than air or oil, stray flux that can cause core losses is minimized.
Hysteresis loss can be reduce by using material having least hysteresis loop area. hence
silicon steel or high grade steel is used for manufacturing of a transformer core as it is
having very less hysteresis loop area. ... Hysteresis losses can be reduced by increasing
the number of laminations.
4. What is meant by eddy current losses?
Eddy current loss is conductive I2R loss produced by circulating currents induced in
response to AC flux linkage, flowing against the internal resistance of the core.
5. How hysteresis loss can be reduced?
Hysteresis loss can be reduce by using material having least hysteresis loop area. hence
silicon steel or high grade steel is used for manufacturing of a transformer core as it is
having very less hysteresis loop area. ... Hysteresis losses can be reduced by increasing
the number of laminations.