The minimum insulation resistance of new, cleaned or repaired windings with respect to ground is 10 Megohm or more. The minimum insulation resistance, R, is calculated by multiplying the rated voltage Un, with the constant factor 0.5 Megohm/kV.
What is the minimum insulation resistance of a motor?
Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm. For example, a motor rated at 2,400 volts should have a minimum insulation resistance of 2.4 megohms.
How do you calculate insulation resistance?
How is insulation resistance calculated and tested? We should all be familiar with Ohm’s law. If we apply a voltage across a resistor and then measured the consequential current flow, we can then use the formula R=U/I, (where U=Voltage, I=Current and R=Resistance) to calculate the resistance of the insulation.
How do you find the IR value of a motor?
(4) IR Value for Electric motor:
- For rated voltage below 1KV, measured with a 500VDC Megger.
- For rated voltage above 1KV, measured with a 1000VDC Megger.
- In accordance with IEEE 43, clause 9.3, the following formula should be applied.
- Min IR Value (For Rotating Machine) =(Rated voltage (v) /1000) + 1.
What is motor insulation resistance?
Insulation Resistance (IR) is among the most common motor tests. … In an IR or megohm test the voltage applied and the total leakage current are measured between the windings and the motor frame/ground.
How do you find the insulation resistance of a 3 phase motor?
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.
How do you test for insulation in a motor circuit?
Place one meter lead on the ground terminal or wire and place the other meter lead on one of the phase wires or terminals. Press TEST on the meghometer. A very high resistance reading (generally greater than 10 megaohms) will indicate the motor insulation is good.