Multiple tests are carried out to ensure the performance of a transformer before it is delivered to the customer. The main tests used for this verification are the following:
No-load Voltage Test: the primary voltage of the transformer is applied to its input with no external load applied to the output. The objective of this test is to verify that the output voltage is close to that expected, that there is no voltage loss and that there are no abnormal vibrations.
Short Circuit Voltage Test: a known current (1-5%) is passed through the secondary winding with no load applied to the output. The objective of this test is to verify that the short-circuit current is in line with the transformer rating and that there are no abnormal overheating or vibrations.
Efficiency test: the transformer is tested under load with a known power to measure the efficiency with which it transfers energy. This test is important for determining the overall energy efficiency of the transformer and for detecting any energy loss problems.
Impedance test: is used to verify the electrical properties of the transformer. In this case, a known current is passed through the primary winding and the output voltage and the phase difference between the voltage and current are measured. The objective of this test is to determine the overall impedance of the transformer.
Earth Continuity Test: the electrical resistance between the primary winding and the earth mask of the transformer is measured to verify that the metal of the transformer is electrically connected to the earth mask.