This is an insulation test of motor windings, commonly referred to as megging, to megger, or to meg a motor. We are testing the motor’s insulation, more specifically between the motor windings and the motor casing. … Using a megohmmeter properly will test any motor insulation.
Why do you meg a motor?
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 a good megohm reading for 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.
What is a bad Megger reading on a motor?
If the motor is kept in a place with high humidity, a periodical inspection is necessary.
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A general rule-of-thumb is 10 Megohm or more.
| Insulation resistance value | Insulation level |
|---|---|
| 2 Megohm or less | Bad |
| 2-5 Megohm | Critical |
| 5-10 Megohm | Abnormal |
| 10-50 Megohm | Good |
Can you meg a motor?
Well, if we’re nit-picking, technically speaking, you can’t ‘Megger’ a motor. Megger is a registered trademark, not a verb, but we get it – old habits die hard.
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 Meg out a 3 phase motor?
- 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. …
- Crank the handle for about a minute, and notice the resistance reading.
How much resistance should a motor have?
Earth 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.
How do you know if a 3 phase motor is bad?
Using Ohm meter: Disconnect all power from machine. Check all three wires singly T1,T2,T3 (all three phases) to the ground wire. Readings should be infinite. If its zero or reads any continuity at all, then a problem exists with either the motor or cable .
What is a bad Meg reading?
When a motor reads 0 ohms this is a dead short or “grounded”, “Fried”. . We used a rule of thumb of anything under 20 megohms was bad. after that it was questionable until after 50 meg. When are readings went towards infinity we knew it to be good.
What does a reading of 0 ohms mean?
Ohms is a measurement of resistance so “zero ohms” means no resistance. All conductors offer some resistance, so technically, there is no such thing as zero ohms.
What should a 480V motor Meg?
IEEE recommends that for motor starting that the operational voltage, expressed as a meg-ohm value doubled plus 1000 is the minimum meg value for starting. For a 480V motor that would mean . 480Meg x 2= . 960 Meg + 1000, so a minimum ground resistance for starting a 480V is 1.960 Meg or round up to 2 meg-ohms.
How do I know if my electric motor is bad?
How to Check an Electric Motor If It Is Bad
- Small fan motors last a long time due to few moving parts. …
- Ball bearings in motors can wear out without lubrication. …
- Power saw motors have brushes that wear out. …
- Test for direct shorts in the motor’s power windings in induction (non-brush type) motors. …
- Examine the relay and contacts on relay-start induction motors.
How do you test if a motor is down to earth?
Touch the meter’s second probe to one of the motor’s wire terminals. Read the meter. The meter should read infinite. If not, then the motor’s windings are shorted to ground.
What does a high ohm reading mean?
Higher numbers indicate a higher resistance rating, which means more energy will be required to integrate the component in a circuit. When you test a resistor, capacitor, or another electronic component, the ohmmeter will display a number indicating its resistance.