Question: Why Do You Megger A Motor?

What does a 0 reading on an ohmmeter mean?

Ohmmeter is an instrument used for measuring resistance of a component or a circuit.

Resistance is measured in ohms with no current flowing through the circuit.

It indicates zero ohms when there is no resistance between the test points.

This shows continuity of current flow in a closed circuit..

How many ohms should a motor read?

0.5 ohmsEarth Continuity and Resistance Test A good motor should read less than 0.5 ohms. Any value greater 0.5 ohms indicate trouble with the motor.

Can a Megger kill you?

The megger supplies over 500 volts, and that is enough to give a fatal shock.

What is considered a bad Megger reading?

Turn on and read the meter. 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 can I increase my Megger value?

Example-1: For 11KV, Three Phase Motor. IR Value =0.415+1=1.41 MΩ but as per IEEE43 It should be 5 MΩ….IR Value of Motor as per NETA ATS 2007. Section 7.15.1.Motor Name Plate (V)Test VoltageMin IR Value1000V1000V DC100MΩ2500V1000V DC500MΩ5000V2500V DC1000MΩ8000V2500V DC2000MΩ5 more rows•Apr 29, 2012

How much voltage does a Megger put out?

Working Principle of Megger Test 500 Volt DC is sufficient for performing test on equipment range up to 440 Volts. 1000 V to 5000 V is used for testing for high voltage electrical systems.

Can a Megger damage a motor?

Never use a megger if the motor windings are under a vacuum. … 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 does a Megger work?

Definition: The Megger is the instrument uses for measuring the resistance of the insulation. It works on the principle of comparison, i.e., the resistance of the insulation is compared with the known value of resistance. … The accuracy of the Megger is high as compared to other instruments.

How do you test to see if a motor is bad?

With a multimeter set to low ohms (usually 200), test between each winding terminal and the metal casing of the motor. If there is any reading on any of these then the motor is bad, do not use it. You may find that when it runs ungrounded that the casing becomes live at up to supply voltage.

What is a bad insulation resistance reading?

The purpose of the IR test is to check for damaged insulation, this can be mechanical damage or damage by heat, (overloaded cables), readings less than 2 Mohm indicate damaged insulation, readings of 2-50 Mohm are indicative of long circuit lengths, moisture and contamination and do not indicate the insulation quality, …

How do you read Megger results?

If the megger reads a resistance under 1 (1,000 ohms) on your meter after the initial 60-second interval, the cable has failed and the cable should be removed. If the megger reads a resistance between 1-1.25 on your meter, then the cable passes. Any reading above 1.25 is considered excellent.

Can you Megger a motor phase to phase?

You can meg from one winding to another as long as there is no connection between the two. The internal connection of the wye point on a wye connected motor will prevent testing between the windings internally connected but you could test from these three to the other windings.

What are the applications of Megger?

The device enable us to measure electrical leakage in wire, results are very reliable as we shall be passing electric current through device while we are testing. The equipment basically uses for verifying the electrical insulation level of any device such as motors, cables, generators, windings, etc.

What does Megging a motor tell you?

Megger testing measures resistance between the phase windings of the motor under test and ground. If there is an insulation breakdown, the resistance is negatively impacted and there is a departure between phases or between one measurement and a previous one and a determination of motor health is made.

What is insulation resistance of motor?

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. Ohms law is applied to calculate the resistance in megohms.

Why do we Megger a motor?

To measure the resistance in a three-phase motor, you will need a megohmmeter, otherwise known as a megger. Unlike an ohmmeter, a megger can measure high-voltage resistance values, which are generally the kinds of values you will encounter with three-phase motors.

What is the acceptable Megger reading for a motor?

The rule may be stated: 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.

What is the primary function of a Megger?

Definition: The Megger is the instrument uses for measuring the resistance of the insulation. It works on the principle of comparison, i.e., the resistance of the insulation is compared with the known value of resistance.

Is a Megger AC or DC?

Megger is an instrument used for measuring insulation resistance of a cable, but the cable that is to be tested is used in AC lines and the megger uses DC as the testing voltage.