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Five electrical transformers tests to conduct before installation

Sarah Mead, Editor


Tags: Test & Measurement

Topics: Test & Measurement

A lot of public and industrial appliances use transformers to increase and decrease the electrical voltages, and you will be able to spot them everywhere these days. Now if a new transformer is being installed, it is necessary that it goes through some tests. These tests are done to make sure that the transformer has mechanical, electrical and thermal sustainability with the system it will be serving. Here are several different kinds of tests that must be conducted before a transformer’s installation.

Megger Test

This test is also known as Insulation resistance test and is done to gauge the quality of insulation within the transformer. The test is conducted using a high capacity megohmmeter. The results of the test may vary depending on the insulation’s temperature and cleanliness of the transformer. To pass the test, it is necessary for the transformer to show a higher resistance than what is prescribed for that specific model by international standards. For completion of the test, it is essential to measure the resistance between all the windings, and between the ground and the windings.

Oil Test

Oil tests are not just crucial during installation, but they must be conducted regularly. Regular testing of transformers is also very important to make sure that the system is running smoothly. Oil functions as an insulation and cooling provider for transformers. The oil test observes several things including, acid number, power factor, dielectric breakdown, moisture content and interfacial tension. To put it in simple words, oil tests gauge the condition of the insulation & the oil.

Turns Ratio Test

This test is run to make sure that the transformer will decrease or increase the voltage as it is required. The windings of both the coils (primary & secondary) have to follow the right specifications. The result can be calculated by dividing the number of turns of both coils. If the function of the transformer is to increase the voltages, then the primary coil must have lesser turns than the secondary coil. And if the transformer is installed to decrease the voltages, then the primary coil must have more turns than the secondary windings.

Resistance Test

Resistance testing makes sure that the wiring of the circuit is proper and all the connections and tightly joined. This is to determine if there is any resistance in the windings. If all the connections are not correctly linked, or circuit is not appropriately wired, the transformer may lose voltages. This can also lead to a short circuit and can cause severe damage. The test is usually conducted when the transformed is at the same temperature as its surroundings and is not conducting any current.

Polarity Test

This is a straightforward test and is done to make sure that all the windings in the transformer are connected in a similar fashion. The purpose of this test is to make sure that the current is flowing in one direction. Wrong connection in winding can cause the current to move in the opposite direction, which can cause severe damage to the transformer and as well as the system it is connected to. This test becomes a vital one when several transformers are connected parallel to each other.

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