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Insulation Resistance (IR) Test (3 Phase Induction Motor) : Published On July 1, 2020

This document describes how to perform an insulation resistance test on a 3-phase induction motor. The test involves measuring the resistance between motor windings using a megger tester to check the health of the motor insulation. The procedure involves disconnecting power, isolating each winding, applying 500V DC, and measuring the resistance which should ideally be infinity but practically in the gigohm range for good insulation. Values below 10 megohms indicate low insulation resistance risking overheating and short circuits.

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Jawad Khan
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709 views9 pages

Insulation Resistance (IR) Test (3 Phase Induction Motor) : Published On July 1, 2020

This document describes how to perform an insulation resistance test on a 3-phase induction motor. The test involves measuring the resistance between motor windings using a megger tester to check the health of the motor insulation. The procedure involves disconnecting power, isolating each winding, applying 500V DC, and measuring the resistance which should ideally be infinity but practically in the gigohm range for good insulation. Values below 10 megohms indicate low insulation resistance risking overheating and short circuits.

Uploaded by

Jawad Khan
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Insulation Resistance (IR) Test ( 3 Phase

Induction Motor)
 Published on July 1, 2020 Jawad Khan

Insulation Resistance test of 3 Phase Induction Motor

Squirrel Cage Induction motor for industrial Purposes.

IR For Motors:
It’s a nondestructive test which is used to check the health of
motor by measuring the insulation Resistance between the
windings using Megger (Tester ).
Tester:
 Megger (Mega Ohm Meter, it’s a high resistance range ohm
meter which is used to get the Ohmic value of the insulation
under the DC voltage of great stability .

Applicable standard:

IEEE STANDARD 43-200/43-2013

TEST Procedure:
1)     Disconnect the motor from power supply using main
breaker

2)     Use do not operate tag to avoid injury

3)     Open the motor terminal box


4)     Check for current using the tester/Ground motor terminals /
short motor terminals for safety purpose to avoid getting shock

5)     Remove the links / nuts to isolate the windings from each


other
6)     Windings ends may be six or three depends on the
manufactures
7)     After isolation of windings now we have to measure the
insulation resistance between the windings by using megger

8)     select 500 VDC for 3 phase motors


9)     After connection and apply voltage for 10 seconds (or until
readings becomes stable 10 seconds are enough mostly)

10)  Note the values


11)  Repeat the test for between all the three windings ( total
number of phases 3 )

Result:
Ideally The ohmic value should be infinity which is not possible
practically
The practical values should be in Giga Ohms, like
3GΩ,3.5GΩ,5GΩ,6GΩ where 6GΩ or above means the
insulation of the windings are very very good.
Also these values can be in MΩs

Below 10MΩ the motor will burn as the insulation Resistance


will be very low, will become hot and short circuit.

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