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ANADOLU UNIVERSITY
DEPARTMENT OF
ELECTRICAL AND ELECTRONICS ENGINEERING
EEM 311
Principles of Energy Conversion Laboratory
Fall, 2014-2015
Experiment 5 :
Three-phase Transformer Connections and
Determination of Voltage Regulation
ANADOLU UNIVERSITY
EEM311 – Experiment 5
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Purpose :
Using the three-phase transformer provided, to realize possible three-phase transformer
connections and verify rated line voltages and currents with measurements. For all possible three-phase
transformer connections, the voltage regulation will be determined.
Background and Theoretical Discussion :
Three-phase transformer banks are design either using a single three-phase transformer, which has
internal connection depending upon the application or using three single-phase transformers, which are
connected in any possible way that the application requires. As long as the redundancy is concerned,
using three singlephase transformers has some advantages. One of which is that; if one of the transformer
fails, threephase power can still be obtained by using two singlephase transformers at the cost of loosing
some fraction of the rated power.
The possible three-phase transformer connections are;




Delta Delta Δ−Δ
Wye Delta Y −Δ
Delta Wye Δ− Y
Wye-Wye Y − Y
The voltage regulation of a transformer under load condition is defined as the difference between
the noload voltage and the load voltage when the primary voltage and the frequency remain unchanged.
The voltage regulation actually gives the percent of value of required change in primary in order to keep
the secondary voltage constant. Percent regulation is given as
%V
V2 no load  V2load
100
V2 no load
Equipment List :
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DL 1013M2
Power Supply
1
DL 1031
Digital Power Measuring Unit
1
DL 1080
Three Phase Transformer
1
DL 1017R
Resistive load bank
1
DL 1017L
Inductive load bank
1
Wavetek
Hand Multimeter
ANADOLU UNIVERSITY
EEM311 – Experiment 5
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Procedure :
1- In the laboratory, you will be provided with a transformer bank of 6 single-phase transformers each
rated 190V / 70V as depicted in Figure 1. The bank with 6 transformers has a rated total power of
1000VA.







First, connect upper transformers with lower ones in series to obtain three 380V / 140V
single-phase transformers.
Next, connect 3 single-phase transformers as a three-phase Delta Wye transformer bank,
Figure 2, and connect low voltage side to R & L load bank.
In this configuration, without applying the power to the experimental setup, calculate rated
line voltages and currents. Verify your results with your T.A.
Once your calculations are correct adjust load banks so that very low secondary current will
flow, and apply rated primary voltage to the setup.
Then adjust load banks to draw rated primary current.
Record primary current and voltage and measure secondary voltage using handheld
multimeter.
Compare measurements with your calculations.
ANADOLU UNIVERSITY
EEM311 – Experiment 5
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2- Adjust primary to rated voltage and keep it at that value. Using only R load (unity power factor) and
RL load (lagging power factor) fill out the following table by loading the transformer at fractions of
rated primary current.
DELTA WYE CONNECTION
cos φ
Load
position
I
Irated
I / Irated
V2no-load
V2load
%V
1
2
3
1
(resistive)
4
1.52 A
5
6
7
1
2
3
t.b.a.
(inductive)
4
1.52 A
5
6
7
t.b.a.: to be arranged by your assistant
ANADOLU UNIVERSITY
EEM311 – Experiment 5
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3- Repeat steps 1 and 2 for Delta Delta connection.
DELTA DELTA CONNECTION
cos φ
Load
position
I
Irated
I / Irated
V2no-load
V2load
%V
1
2
3
1
(resistive)
4
1.52 A
5
6
7
1
2
3
t.b.a.
(inductive)
4
1.52 A
5
6
7
t.b.a.: to be arranged by your assistant
Important !
All groups must perform rated line voltage and current calculations and verify the correctness of
the results with T.A.s . If a group fails to calculate them correctly, that group will not be allowed to
perform the measurements. This basically means that you will fail this laboratory assignment. One way of
avoiding this trouble is that, since you have all necessary data, you make your calculations before coming
to laboratory. Then you will make your measurements and go.
Report :
1. Present your line current and voltage calculations for three-phase transformer connections and
compare them with measured results.
2. Present your percent regulation results and plot percent regulation versus loading (x axis) for both
resistive and inductive loading on the same graph. Explain the fact that under the lagging power
factor loading percent regulation is higher
3. Comment if there is any significant variations in percent regulation under same loading but
different three-phase connections.
ANADOLU UNIVERSITY
EEM311 – Experiment 5