Basic Electrical Engineering

1. Maharashtra Institute of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE :Efficiency & Regulation of single phase Transformer.
EXPERIMENT NO.13 : MIT(T)/ETC/Basic Electrical Engineering /Manual No.1
FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electrical Engineering Location Part I Page 58
Aim: Efficiency & Regulation of single phase Transformer.
Apparatus: 1.AC Ammeter (0-5A) 2.AC Ammeter (0-10A) 3.AC Voltmeter (0-300V) 4.AC
Voltmeter (0-150V) 5. Wattmeter 5A, 250V
Theory:
Efficiency
In a practical transformer we have seen mainly two types of major losses namely core and copper
losses occur. These losses are wasted as heat and temperature of the transformer rises. Therefore
output power of the transformer will be always less than the input power drawn by the primary
from the source and efficiency is defined as
Efficiency=
Output power KW
Output power KW +Losses
Efficiency=
Output power KW
Output power KW +Core Loss+Copper Loss
Regulation
The output voltage in a transformer will not be maintained constant from no load to the full load
condition, for a fixed input voltage in the primary. This is because there will be internal voltage drop in
the series leakage impedance of the transformer the magnitude of which will depend upon the degree
of loading as well as on the power factor of the load. The voltage regulation is the percentage of
voltage difference between no load and full load voltages of a transformer with respect to its full load
voltage.
Regulation=
E2−V2
V2
X100
Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable

2. Maharashtra Institute of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : Efficiency & Regulation of single phase Transformer.
EXPERIMENT NO.13 : MIT(T)/ETC/Basic Electrical Engineering /Manual No.1
FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electrical Engineering Location Part I Page 59
The knowledge of regulation gives us idea about change in the magnitude of the secondary voltage
from no load to full load condition at a given power factor. This can be determined experimentally by
direct loading of the transformer. To do this, primary is energized with rated voltage and the secondary
terminal voltage is recorded in absence of any load and also in presence of full load.
Circuit Diagram
Procedure:
1. Connections are made as per circuit diagram. Primary side voltage is adjusted at rated value (115V)
by a variac on no load.
2. By varying lamp load in suitable steps, readings are taken for all meters from no load to full load.
The primary rated voltage is kept constant throughout the test using variac.
3. Various observations are recorded in tabular form, as given below.
Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable

3. Maharashtra Institute of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : Efficiency & Regulation of single phase Transformer.
EXPERIMENT NO.13 : MIT(T)/ETC/Basic Electrical Engineering /Manual No.1
FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electrical Engineering Location Part I Page 60
Observation table:
Sr .
No
Primary side Secondary side Calculations
V1
(Volt)
I1
(Amp)
W1
(Watts)
V2
(Volt)
I2
(Amp)
O/P = V2 x
I2 (Watts)
%η =
(V2 x I2) /
W1
%Regn
=
[(E2 – V2) / E2]
x 100
1
2
3
4
5
6
Sample Calculations:
Output power = V2I2COSΦ2
% Efficiency (%η) = ---------------- x 100 = ------------------ x 100
Input power W1
As load is resistive (COSΦ = 1) Being lamp load. Calculate for sr. no. 2 observation. Regulation –
under no load condition (i.e. when secondary circuit is open and I2 = 0). The voltmeter reading
secondary side gives no-load secondary terminal voltage (E2).
Regulation=
E2−V2
V2
X100
Where V2 = voltage at full load
Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable

4. Maharashtra Institute of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : Efficiency & Regulation of single phase Transformer.
EXPERIMENT NO.13 : MIT(T)/ETC/Basic Electrical Engineering /Manual No.1
FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electrical Engineering Location Part I Page 61
Graph: The result obtained, curves are plotted for efficiency and regulation against output power.
Conclusion: The efficiency and regulation at any desired load can be found from the graphs. This
method is suitable for a small capacity transformer. For a large transformer, we have to use the indirect
method e. g. by performing the O.C. and S.C. test on transformer.
Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable