Insulation Resistance Test Standard For Motor

Historically many field electricians use the somewhat arbitrary standard of 1 megohm per kv.

Insulation resistance test standard for motor.

Hands down without a doubt one of the most universally searched topics on ec m s website from a historical perspective is insulation resistance testing as a result some of our most popular evergreen articles like understanding insulation resistance testing continue to top the charts when it comes to most popular content. A rated line to line voltage for three phase ac machines line to ground voltage for single phase machines and rated direct voltage for dc machines or field windings. Ground insulation test of a motor. Set the voltage.

Figure 4 typical record of insulation resistance of a mill motor. For 11kv equipment mi. At a the insulation resistance decreases due to aging and dust accumulation. Based upon equipment rating.

One meg ohm rule for ir value for equipment. Since 80 of electrical maintenance and testing. For a three phase motor insulation resistance is usually measured between each motor winding or phase and between each motor phase and motor frame earth using an insulation tester or megger. Values based on ieee std 43 2013.

Z 5 date of test r eading in megohms the graph below shows an example of the insulation resistance readings on an electric motor. For a 440v motor minimum ir between phase and ground 440 1000 1 1 44 megohm example 2. Curve a shows test values as measured. Dc voltage of 500 or 1000 v is applied between the windings and the ground of the motor.

As per ie rules 1956. Insulation resistance test insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. Figure 3 typical scale on the megger insulation tester. The measurement of insulation resistance is carried out by means of a megohmmeter high resistance range ohmmeter this is how the test works.

Curve b shows same values corrected to 20 c see page 22 giving a definite downward trend toward an unsafe condition. Ansi neta mts 2015 table 100 11 insulation resistance test values rotating machinery for one minute at 40 c. Minimum insulation resistance ir value is depend upon rated line voltage of equipment. Minimum ir in megohm kv 1 example 1.

1k v 1 mω minimum 1kv 1 mω 1kv. The international electrical testing association neta specification maintenance testing specifications for electrical power distribution equipment and. B kv is the rated machine terminal to terminal voltage. At a pressure of 1000 v applied between each live conductor and earth for a period of one minute the insulation resistance of hv installations shall be at least 1 mega ohm or as specified by the bureau of indian standards.

During the measurement and immediately afterwards some of the terminals carry dangerous voltages and must not be touched. A if the insulation resistance of a new cleaned or repaired motor that has been stored for some time is less then 10 mω the reason might be that the windings are humid and.