You are watching: How to megger a 3 phase motor

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The straightforward steps in ascertaining the health of a three-phase AC engine are offered below:(a) basic Inspections(b) earth Continuity and also Resistance Test(c) strength Supply Test(d) AC motor Winding continuity Test(e) AC motor Winding Resistance Test(f) Insulation Resistance Test(g) running Amps Test
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General Inspections
For the three-phase motor, execute the following:(1) inspect the figure of the motor. Inspect for burnt, damage to body or cooling pan or shaft.(2) Manually turn motor tower to examine bearing condition. Look out for smooth and complimentary shaft rotation. If column rotation is totally free and smooth, bearing is maybe in great condition, otherwise think about replacing, fix or lug out additional diagnosis.(3) just like all testing and also inspections, the motor name plate provides an useful information that will assist to ascertain the true health and wellness of the motor. Examine the surname plate thoroughly and compare values of to run amps test (see below) with name bowl valueEarth Continuity and also Resistance TestWith a multimeter, measure up the resistance in between motor framework (body) and also earth. A an excellent motor should read much less than 0.5 ohms. Any kind of value greater 0.5 ohms show trouble with the motor. Further troubleshooting maybe requiredPower it is provided TestFor three phase motors, the expected voltage for a 230/400V mechanism is 230V step to neutral and 400V in between each the the three phase supply lines. Examine that the correct voltage is applied to the motor utilizing a multimeter. For sure the terminal for power supply is in good condition. Examine the link bar for terminal (U, V, and also W). For 3 phase motors, connection type is one of two people Star (Y) or DeltaAC motor Winding continuous TestUsing a multimeter, check the continually of motor winding from phase to phase ( U come V, V to W , W come U ).Each step to step must have actually a continually if winding is OK. If any details phase stops working the continually test, your motor is probably burnt.Please see just how to recognize three phase windings for appropriate winding identification. U, V, W is a europe winding designation.AC engine Winding Resistance TestCheck the motor winding resistance or ohms analysis using a multimeter or ohmmeter because that phase to phase terminal ( U to V,V come W ,W come U ).The ohms reading for every winding must be the same (or nearly the same). Remember the the three phases have identical windings or almost so!Insulation Resistance TestInsulation resistance fail of an electric motor is one of the very first signs that the engine is around to fail. Because that a 3 phase motor, insulation resistance is commonly measured between each motor winding or phase and between every motor phase and also motor framework (earth) using an insulation tester or megger. Set the voltage setting of the insulation resistance tester come 500V. Examine from step to phase (U to V, V come W, W come U). Examine from phase to motor structure (earth) (U to E, V to E , W to E ). Minimum test worth of motor insulation resistance is 1 Meg Ohm (1 MΩ).

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See just how to measure insulation resistance of electrical MotorRunning Amps Test
With the engine running, check the full load amps (FLA) v a suitable meter or preferably a clamp top top meter and also compare v the name plate FLA. Deviations indigenous rated FLA can signify difficulties with the engine under test.