Transformer winding resistance measurements are obtained by passing a known DC current through the winding under test and measuring the voltage drop across each terminal ( Ohm's Law). Regardless of the configuration, the resistance measurements are normally made phase-to-phase and the readings are compared with each other to determine if they are acceptable. Winding resistance in transformers will change due to shorted turns, loose connections, or deteriorating contacts in tap changers. Measuring the resistance of transformer windings assures that each circuit is wired properly and that all connections are tight. The main purpose of this test is to check for gross differences between windings and for opens in the connections. Winding resistance measurements are an important diagnostic tool for assessing possible damage to transformers resulting from poor design, assembly, handling, unfavorable environments, overloading or poor maintenance. (ii) Insulation value obtained less than 1Mohm is dangerous for the motor to operate.This guide provides an introduction to transformer winding resistance test methods and procedures. (i) Motor has to be isolated from its source of supply before conducting test (vi) Now compare the reading for all three winding and look for any imbalance. Convert them to actual reading with the given measuring chart. (iv) On connected motor (star/ delta), connect the test clip to two of the supply terminals (RY, BY) and press the operating button. (iii) Connect the test lead terminal marked resistance/ inductance.
(ii) Set the function switch to resistance for taking motor winding resistance and put function switch to inductance for taking inductance of each winding. The insulation value in mohm is indicated in the blue scale. (ii) Connect one test lead to suitable point on the machine frame and other lead to one of the supply terminal. (i) Now connect the test leads to the terminal marked insulation 500v (iii) The needle should deflect more than 70% to indicate good battery (i) Select the function switch to battery (iii) Measuring and comparing the inductance of stator winding and the effect of rotor position on electric motor.
(ii) Measuring and comparing the resistance of stator winding of an electric motor. It is therefore the purpose of the Electric Motor Checker is : They should be equal or any between the values should be within acceptable tolerance limits. s of each phase are measured and compared with each other. Note :The Resistance/inductance value being measured/compared should be same or at least the variation between them must be inside the permissible tolerance-limit. Measurement and comparison of the inductance between the three phases of the stator-winding.Measurement and comparison of the resistance between the three phases of the stator-winding.Insulation measurement with respect to ground.We can identify an electrical defect in it by carrying out : Here we will talk about 3 phase equipments only. But, before carrying out the tests, we should have knowledge of at least its basic fundamentals.
This test may be carried out even if the phase winding is intact (not removed). You can take the reading at any convenient spot on the i/p supply of the motor. You can do it by just switching-off the input supply breaker also. It is not mandatory to remove the input cable. To ensure this, the supply input for the motor has to be cut-off prior starting the tests. This Electric Motor Checker can, however, only be used for a motor which is stationary. Electric Motor Checker is a very useful test equipment that can be used for detecting an electrical-fault (for example – short-circuit, open-circuit, damage of insulating material …… and many more) in case of motors/other 03 phase equipments in the fastest and easiest way.
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