Download Experiment 2 - Single Phase Transformer

UNIVERSITI MALAYSIA PERLIS
ELECTRICAL ENGINEERING TECHNOLOGY
EMT 113/4
EXPERIMENT 2
SINGLE PHASE TRANSFORMER
– Voltage and Current Ratios
MARKS
Result &
Calculation
58
Discussion
Conclusion
Total
%
9
5
72
100
NAME
PROGRAMME
MATRIX #
GROUP
DATE
EMT113/4
Single Phase Transformer-Voltage and Current Ratios
EXPERIMENT 2
TITLE: SINGLE PHASE TRANSFORMER – VOLTAGE AND CURRENT RATIOS
OBJECTIVES
1.
2.
To familiar with voltage and current characteristics of a single phase transformer.
To be able to use the transformer turns ratio to predict the voltage and current
that will flow in the secondary winding.
EQUIPMENTS
EMC Workstation Model 8110
Single Phase Transformer Model 8341
Power Supply Model 8821
Data Acquisition Interface Model 9062.
INTRODUCTION
The windings of a standard single-phase transformer are called the primary
winding and the secondary winding. The primary winding is the power input
winding and this is the side that is connected to the ac power source. The
secondary winding is connected to the load and is physically and electrically
isolated from the primary. The voltage and current that flow in the secondary are
related to the primary voltage and current by the transformer turns ratio N1/N2 (or
Np/Ns) through a very simple relationship. The ratio of primary voltage to
secondary voltage equals N1/N2, while the ratio of the primary to secondary is
equal to the inverse of the turns ratio, N2/N1. This result in the following,
EPRI = N1
ESEC
N2
which gives:
ESEC
= EPRI
X
N2
N1
and
IPRI = N2
ISEC
N1
which gives:
ISEC
= IPRI
N1
N2
X
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
1
EMT113/4
Single Phase Transformer-Voltage and Current Ratios
PROCEDURE
CAUTION
High voltages are present in this laboratory exercise! Do not make or modify any
banana jack connections with the power on unless otherwise specified!
Figure 2-1: Single –Phase Transformer Measurements
1. Install the Power Supply, Data Acquisition Interface (DAI) and Single-Phase
Transformer modules in the EMS Workstation.
2. Make sure that the main switch of the Power Supply is set to the O (OFF)
position, and the voltage control knob is turned fully counter clock-wise (ccw). Set
the voltmeter select switch to the 4-N position.
3. Ensure that the DAI LOW POWER INPUT is connected to the main Power
Supply and set the 24V-AC power switch to the 1 (ON) position.
4.
Display the Metering application.
5. Set up the transformer circuit shown in Figure 2-1. Connect E1 and I1 as shown
and use E2 to measure the different secondary voltages.
6. Turn on the power and adjust the voltage control for the value of Es given in
Figure 2-1.
7. Measure the transformer primary current (IPRI) and all the different terminal
voltages (E1-2 to E9-6). Record your data in the sheet provided.
8. After recording the measurements, rotate the voltage control fully ccw and then
turn off the power.
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
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EMT113/4
Single Phase Transformer-Voltage and Current Ratios
Note: When measuring the various voltages, turn off the Power Supply before
modifying the connections of the DAI to the circuit.
Figure 2-2: Determining the ratio of Primary Current to Secondary Current
9. Connect I2 as shown in Figure 2-2 and note that it short-circuits secondary
winding 5-6. Turn on the power and slowly adjust the voltage control to obtain the
value of current Is given in Figure 2-2.
10. Record the values of primary voltage (EPRI) and current (IPRI) and the value of the
short-circuit secondary current (ISEC) in winding 5-6.
11. Return the voltage control to zero and turn off the power. Calculate the ratio of
primary current to secondary current. Compare the result with calculated turn
ratios N2/N1.
12. Connect I2 so that it now short-circuits secondary terminals 3-4. Turn on the
Power Supply and slowly adjust the voltage control knob for the same value of
current used in step 9. Once again, record the values of primary voltage (EPRI)
and current (IPRI) and the secondary winding current (ISEC).
13. Return the voltage control to zero and turn off the power. Again, calculate the
ratio of primary current to secondary current. Compare the result with calculated
turn ratios N2/N1.
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EMT113/4
Single Phase Transformer-Voltage and Current Ratios
Figure 2-3: Effect of Core Saturating on Exciting Current
14. Set up the transformer circuit shown in Figure 2-3. It will be used to show how
exciting current is affected when the transformer core becomes saturated. Since
the exciting current is so small, the corresponding voltage across a sense
resistor R will be used to illustrate its variation. Connect the transformer primary
terminals to Power Supply terminals 4 and 5 through sense resistor R. Connect
E1, E2 and E3 to measure the transformer voltages.
15. Turn on the power and use the output voltage control to obtain values for E2
equally spaced at about 10% intervals over the complete control knob range. At
each voltage adjustment, click the Record Data button to enter the
measurements in the Data Table. Then, record your data in a table. When all
data values have been recorded, rotate the voltage control fully ccw, and turn off
the Power Supply.
Table 2-1 Transformer Voltages Data
Interval,
%
0
Sensed Voltage
(E1), V
Primary Voltage
(E2), V
Secondary Voltage
(E3), V
10
100
16. Display the Graph screen, select E1 as the X-axis parameter and E2 as the Yaxis parameter. Click the Line Graph button to observe the curve of primary
voltage versus exciting current, represented by E1. Then copy this graph into the
graph paper provided with appropriate scale, correct axis parameters and graph
title.
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EMT113/4
Single Phase Transformer-Voltage and Current Ratios
17. Review the measured data to determine how the primary-to-secondary voltage
ratio was affected when the transformer core become saturated.
18. Ensure that the Power Supply is turned off, the voltage control is fully ccw and
remove all leads and cables.
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
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EMT113/4
Single Phase Transformer-Voltage and Current Ratios
Name:______________________________
Matric No:____________________
Date:____________________________
Course:______________________
RESULTS
Note: Your results should include:
1) Transformer primary current and the different terminal voltages.
(9 M)
Instructor’s Approval :_________________________________________ (1 M)
2) Values of primary voltage (EPRI) and current (IPRI) and the value of the short-circuit
secondary current (ISEC) in both short circuit secondary terminal 5-6 and 3-4. (6 M)
3) The ratio of primary current to secondary current for the two cases above, and
compare results with turn ratios.
(4 M)
4) Table for Transformer voltages.
(33 M)
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
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EMT113/4
Single Phase Transformer-Voltage and Current Ratios
Name:______________________________
Matric No:____________________
RESULTS
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
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EMT113/4
Single Phase Transformer-Voltage and Current Ratios
Name:______________________________
Matric No:____________________
(5 M)
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
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EMT113/4
Single Phase Transformer-Voltage and Current Ratios
Name:______________________________
Matric No:____________________
DISCUSSION
1. The transformer windings between terminals 1 and 2 and between terminals 5
and 6 each have 500 turns of wire (refer figure 2.1). The number of turns in the
winding between terminals 3 and 4 is 865. Calculate the turns ratios between the
primary and secondary windings for each case. Compare these transformer turns
ratios with the corresponding voltage ratios from your experiment. Are they
approximately the same?
(3 M)
2. What can you say about the primary and secondary winding in standard singlephase transformer?
(4 M)
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3. From graph, determine how the primary-to-secondary voltage ratio was affected
when the transformer core become saturated.
(2 M)
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OP-AMP SINEWAVE 'NON-INVERT'
output voltage input
EMT113/4
Single Phase Transformer-Voltage and Current Ratios
Name:______________________________
Matric No:____________________
CONCLUSION
Conclude what you have learned about how to evaluate the current value.
(5 M)
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