Motor insulation
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For a 380V motor, the insulation resistance to ground is 0.2 MΩ. Can it be used?
The general requirement is that the insulation to ground be greater than or equal to 0.5 M ohms.
It’s a bit uncertain; I’m not sure what instrument was used to measure your 0.2M ohms. As mentioned above, the general requirement is at least 0.5M, but I’ve also encountered cases where it was only 0.1M; as long as the resistance measured with a multimeter is in the range of a few hundred ohms, it can still be used.
The motor of my equipment (15 KW) has been left exposed to wind and rain outside the equipment for several years; before use, the wires were connected directly... to the ground. I’m quite worried about this – what potential hazards might there be? ?
It cannot be turned on; check whether it is damp or the insulation has aged.
It cannot be used; find out what is causing such low insulation on the motor. After drying treatment, ready for use
In most cases, this is caused by high moisture content in the motor’s wiring terminals. By removing the wiring covers and simply drying them in the sun, the resistance will definitely be greater than 2 M ohms when measured again.
1. For ordinary motors that have been used, the insulation requirement is that for a working voltage of 220V, the insulation resistance should be no less than 0.22 MΩ; for a working voltage of 380V, it should be no less than 0.38 MΩ. In other words, the resistance relative to ground should be no less than 0.22 MΩ, and the resistance between phases should be no less than 0.38 MΩ. 2. The above refers to the use of a 500V megohmmeter. 3. These data cannot be used as a standard for new motors or motors that have just been repaired.
It can’t be turned on! Use the drying method first! Dry it at 55 degrees! The resistance might be a bit higher!
First, consider what type of motor it is. Ordinary motors cannot be used as they need to be modified; this isn’t necessarily the case for submersible pumps
To test 380V motors, a 500-volt insulation resistance meter should be used; the stator windings are required to have an insulation resistance of no less than 1000 ohms per volt of operating voltage, while the rotor windings must have an insulation resistance of no less than 500 ohms per volt of operating voltage. This applies to wound-rotor motors. Therefore, for motors with a rated voltage of 380 volts, the resistance should not be lower than 0.38 MΩ; achieving this value ensures safe power supply. The testing standards require that for motors with a voltage of 500 volts or less, the resistance should be no less than 0.5 MΩ.