In the foundry I worked in they showed me how to test a three phase motor with a ohm meter well I now work for a company and they say you can not properly test a three phase motor with an ohm meter that a motor megger must be used to properly test a three phase motor and they used it by going from the … Ideally the test should be done phase to ground and phase to phase but, of course, phase to phase is not possible if you only have 3 wires from the motor. With the other test tip, touch the motor grounding screw. For a three-phase motor, the isolation resistance can usually be measured between each motor winding or phase and between each motor stage and motor frame (earth) by an insulation tester or Megger 4. - reversing the motor is possible but does require access to enough winding leads to reverse the electrical phase between the run and start windings. Note that unlike a three phase motor, a single phase motor usually … When we do on-site PI testing, we do it at the MC. If the megs are low, then we un-terminate the motor. Reverse side of card (at right) is used to record the test data. Hand crank for a minute. You can do a winding balance check by comparing the 3 phase … Curve A shows test values as measured; Curve B shows same values corrected to 20°C (see page 22), giving a definite downward trend toward an unsafe condition. This article looks at these systems and the ways to test them. (Some units may also incorporate a hand generator to produce high voltage levels. To megger test a 3-phase motor with a 1000volt megger tester: Switch off the circuit breaker. Turn the handle and look for reading between 20 and 30 megohms. Test the motor circuit by placing one of the Megger tests leads on any of the cables. Figure 3–Typical scale on the Megger … PI test (polarization index) is very effective for trending. Megger trending is common practice in the motor industry. Check for ground continuity, a terminal box bolt. Many simple "across the line" single-phase and 3-phase motors (used in household appliances and industry respectively) can be checked simply by changing the range of the ohm meter to the lowest offered (R X 1), zeroing the meter again, and measuring the resistance between the leads of the motor. The Megger applies a … This way we test the cables also. A three-phase system consists of three single phase AC supplies sharing its return path. Remove the motor circuit using a flat screwdriver. But before starting turn off all power sources to machine then disconnect the 3- phase motor lines ONLY from the drive. But the Megger provides a much higher voltage rather than the ohm meter’s typical three-volt test voltage derived from an internal battery. There isn't a lot that can be done other than to reduce the voltage applied to the motor. For a 480v motor, the test voltage should be 1000v and expect a reading of better than 2M Ohms. Others are designed to accept an input from a high-voltage source.) It is usually done only on the large key motors. With one probe still connected to ground, connect the other test probe to a motor terminal. Set the voltage level of the insulation resistance tester to 500V. I found … BY Triple Phase Training; POSTED IN Latest News WITH 0 COMMENTS; PERMALINK; VIDEO POST TYPE Connect one megger test probe to ground. Figure 4–Typical record of insulation resistance of a mill motor. Servo Motor (3phase 220vac) testing: Below are some basic principles for testing servo motor circuits with meter or megohm meter. This procedure will show you how to test for shorts in windings, cables or opens. Visit ITI Main Site; Contact Us; 01 Dec 2017. Figure 4–Typical record of insulation resistance of a mill motor testing, we on-site! Then disconnect the 3- phase motor lines only from the drive Us 01... A high-voltage source. test for shorts in windings, cables or opens then! 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