Abstract The aim of this report is to investigate and test a transformer and check if it is good to use by doing the following tests continuity test, insulation test, polarity test, open circuit test, close circuit test and voltage regulation test "Load Test". The results of the transformer testing were satisfied and the testing was done successfully. For future improvement testing there should be all the details available in the transformer, using a transformer with very low core, iron and copper losses and using better equipments. In the end the aim and the objectives of this report were achieved.
Table of Contents Abstract... 1 Introduction... 3 Objectives... 3 Transformer Testing... 4 Continuity Test... 5 Insulation Test... 5 Polarity Test... 6 Open Circuit Test... 7 Close Circuit Test... 7 Voltage Regulation Test... 9 Discussion... 10 Conclusion... 10 Table of Figures Figure 1 Continuity Test... 5 Figure 2 Insulation Test... 5 Figure 3 Polarity Test... 6 Figure 4 Open Circuit Test... 7 Figure 5 Close Circuit Test... 8 Figure 6 Voltage Regulation Test... 9 Table of Tables Table 1 Continuity Test Results... 5 Table 2 Insulation Test Results... 5 Table 3 Polarity Test Results... 6 Table 4 Open Circuit Test Results... 7 Table 5 Close Circuit Test Results... 8 Table 6 Voltage Regulation Test Results... 9 2 P a g e
Introduction A transformer is a fixed electrical device that transfers energy by inductive coupling between its winding circuits. An unstable current in the primary winding creates an unreliable magnetic flux in the transformer's core and thus a changeable magnetic flux through the secondary winding. This changeable magnetic flux induces a varying electromotive force (emf) or voltage in the secondary winding. The aim of this report is to do a plenty of tests in the transformers to make sure that it's ready and good to use for safe work environment. Objectives The steps to check a transformer: Choosing a transformer with available information in it like: 1. Is it step up or down transformer? 2. Does it show the value of the primary and secondary, voltage and current value? If not it should not be used or it should be measured. Taking the results from the transformer. 3 P a g e
Transformer Testing There are six type of transformer testing that required in this testing: Continuity Test. Insulation Test. Polarity Test. Open Circuit Test. Close Circuit Test. Voltage Regulation Test. "Load Test". 4 P a g e
Continuity Test Continuity test is used to check if the coil is good or not. If it good the resistance value should be low. Figure 1 Continuity Test Continuity Test Values Primary Secondary Resistance 13ohm 0.223ohm Table 1 Continuity Test Results Insulation Test Insulation test is used to check the insulation of the coil and its job to check if the wires are touching each over or not. If wires are not touching each other the value of the resistance should be as highest as it could be. The value of the resistance was about 11Gohm. Figure 2 Insulation Test Insulation Test Values Primary to Coil Coil to Secondary Secondary to Primary Resistance 11Gohm 11Gohm 11Gohm Table 2 Insulation Test Results 5 P a g e
Polarity Test Polarity test is used to check the polarity of the coil. In polarity test the measuring will determined which the beginning is and which the end in the primary and secondary wires is. If the testing or measuring where from the primary top peak to secondary top peak the voltage should be high, otherwise if the testing was from the primary peak to the secondary ending the voltage should be low. The value of top peak to top peak equal 28.2V and the value of top peak to bottom peak equal to 22.3V which improve the theory of the polarity test. Figure 3 Polarity Test Polarity Test Values primary top peak to secondary top peak primary top peak to secondary bottom peak Voltage 28.2V 22.3V Table 3 Polarity Test Results 6 P a g e
Open Circuit Test Open circuit test used to check the core and the iron loss in the transformer and to determine the no load impedance in the excitation branch of a transformer. In the measuring part by using the wattmeter which will shows the power loss in the circuit from the core and the iron loss. The reason for the core and the iron loss is attributed to eddy current loss and the hysteresis. The open circuit results, the current was about 0.14A, the voltage was about 240V and the power loss was about 9.3Watts. Figure 4 Open Circuit Test Open Circuit Test Primary Values Voltage 240V Current 0.14A Power 9.3W Table 4 Open Circuit Test Results 7 P a g e
Close Circuit Test Close circuit test used to check the copper loss in the transformer and to determine the series branch parameters of the equivalent circuit of a Real transformer. To find the copper lose the power should be found from this formula. The Voltage value was 9.3V, the current value was 0.221A and the power value is 2.1W. Figure 5 Close Circuit Test Close Circuit Test Secondary Values Voltage 9.3V Current 0.221A Power 2.1W Table 5 Close Circuit Test Results 8 P a g e
Voltage Regulation Test Voltage regulation test used to find the efficiency and the voltage regulator of the transformer. Efficiency can be found by using this formula, the efficiency should be closer to 100 so the transformer can be good to use. To found the voltage regulation this formula should be used. Figure 6 Voltage Regulation Test Voltage Regulation Test Values Power Out 35.26W Power In 44W Voltage Load 23V Voltage W/Load 23.64V Efficiency 80.1% Voltage Regulation 2.71% Table 6 Voltage Regulation Test Results 9 P a g e
Discussion What is the purpose of polarity testing? 1) The purpose of polarity testing is to know the start and the end of secondary or primary transformer. 2) To ensure that the color code is correct throughout the whole circuit. 3) To avoid connecting the live wire to earth. How can the PF be determined during the short circuit test? The PF can be determined during short circuit test by using wattmeter, because wattmeter can shows the value of power in it by connecting it to the transformer in open or close circuit tests. The wattmeter will show the value of core, iron and copper loss depending in which circuit is using. How to improve transformer testing? 1) Choosing a better transformer that contain all details about voltage, current and power. Also it should show if it s step down or up transformer. 2) Choosing a transformer that has as low as possible core, iron and copper losses. 3) Using better equipment that can handle high voltage and does it affects in the results and it should be very precise equipments. Conclusion In conclusion the transformer circuit testing was design to show the results of the transformer in each way and without making any shorts to damage the transformer. The objectives of this report were done successfully by choosing a step down transformer and taking all the required results from it. In the end the aim of this report was achieved and the experiment testing and results were obtained and satisfied. 10 P a g e