Friends, today in this article we will learn about the testing of windings. I am going to give you information about all this in a very good way. So let’s start.
Winding Test
Mainly the following types of tests are done to test the windings-
Ground Test
This test is also called earth test. In this test it is seen whether the winding or any part of it is touching the body or not. On touching, the supply enters the structure of the motor and this can be fatal. For this the entire winding is tested. One wire of the testing lamp is connected to any one of the three connections of the motor winding and the other wire is connected to the body or frame of the motor. If the lamp lights up then it is understood that the winding is grounded and if the lamp does not light up then it is understood that there is no earthing in the winding.
If there is a ground fault in the motor, then the star connections of the three phase windings are separated. In this way, the three phase A, B and C windings are separated. Each phase winding is earthed in such a way that if there is no earthing, the lamp does not light but if there is earthing, the lamp lights up. If the connection in the motor is in delta, then all the pairs of its phases are separated so that the winding of each phase is tested.
If it is known that the ground fault is in A phase, then all the joints of the A phase winding are separated. In A phase, all the coils are grounded with a test lamp from the beginning. By doing this, the coil which is grounded and needs to be repaired is identified. After repairing it, it is grounded again. After the fault is rectified, all the connections are restored as they were.
Apart from this, if the insulation is removed or torn while inserting the coil in the slots, the insulation of the wire gets lost and the coil gets earthed. In such a situation, the stripped wire is insulated by applying insulation etc. at this place. Special care is taken while inserting the coil in the slot.
Open Circuit Test
Open means to be open. The test lamp does not light when the coil of the winding is open. In this, both ends of the coil are tested. This open circuit fault occurs due to breakage of a coil turn, separation or looseness of group connection or breakage due to looseness of phase connection. Test lamps are installed on any two ends of the three ends of the motor. There is no fault if the bulb lights up, but this test is done further if the bulb does not light up. If the motor is connected in star, then if the lamp does not light up by connecting the star point and any of the three phases A, B, C, then that phase is open. In a delta connected motor, the windings of all the three phases are separated and a lamp is installed on both ends of A phase. This is an open circuit fault when the lamp does not light up.
Short Circuit Test
A growler is used for this test. It is an inner growler, which is U-shaped. It is a type of electromagnet. This growler is placed on the coil slot. A low range ammeter is installed in series with it. On giving low voltage supply, the growler is rotated on the slots of the entire stator. The ammeter shows the same reading at all places. Hence, the coil is short on the slot where the reading is higher.
What did you learn today :-
Now you must have known about testing of winding and you must have got the answer to all these questions very well.
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