How do you test 3 phase motor insulation?
Phase Resistance: Take the insulation tester and set it to 500V. Take each end and place it on different permutations of L1, L2 and L3 and record each reading. Phase to Earth Resistance: Take the insulation tester, using the same setting, and check each lead from phase to the frame of the motor.
What is the acceptable Megger reading for a motor?
A minimum value of one megohm is needed for insulation resistance. The minimum resistance of 2.4 megohms should be found in the insulation of the motor.
How do you check a 3 phase motor to see if it’s bad?
Using a multimeter, check the continuity of motor winding from phase to phase ( U to V, V to W , W to U ). Each phase to phase must have a continuity if winding is OK. If any particular phase fails the continuity test, your motor is probably burnt.
How do you find the insulation resistance of a 3 phase induction motor?
- Disconnect the motor from power supply using main breaker.
- Use do not operate tag to avoid injury.
- Open the motor terminal box.
- Check for current using the tester/Ground motor terminals / short motor terminals for safety purpose to avoid getting shock.
How do you check motor insulation with a Megger?
How to Test a Three-Phase Motor With a Megger
- Turn off the power supply to the motor, usually accomplished by switching the circuit breaker. …
- Place one megger probe to the any mounting bolt on the breaker box to test for grounding continuity, then touch the other probe to a motor terminal.
Can a megger damage a motor?
Any megger with a higher voltage output than 500 volts DC should be used by an experienced technician. A high voltage for too long of a time may further weaken or fail motor windings and the winding insulation could be damaged by the testing procedure.
How do you increase the insulation resistance of a motor?
Cleaning and drying the winding will usually improve the IR. If the winding temperature is at or below the dew point, moisture may accumulate on the surface, causing low IR values. When the winding is otherwise in good condition, drying will resolve this issue.
What is the resistance of a 3 phase motor?
Most are between 3 and 2.0 ohms. There are 8ohms. A short between phases exists if you read zero.
How many ohms should a 3 phase motor read?
The reading should be between 0.3 to 2 ohms. If it is 0, there is a short. If it is over 2 ohms or infinite, there is an open. You can also dry the connector and retest to possibly get more accurate results.
How do you test a megger?
Press the test button on megger, the megger will generate current. This current flows through cable, the resistance in scale is noted which ranges between 35 to 100 Mega Ohms. Note to maintain this contact for 30 to 60 seconds. Acceptable IR for electrical cable = 1 Mega Ohm for 1000 V.
What is a good megger reading?
Anything reading between 2 megohms and 1000 megohms is usually considered a good reading, unless other problems have been noted. Anything less than 2 megohms indicates an insulation problem.
How do you test for insulation resistance?
To calculate the IR value, apply the voltage, measure the steady-state leakage current (after the dielectric absorption and charging currents have decayed to zero) and then divide the voltage by the current. If the insulation resistance meets or exceeds the required value, the test is successful.