What is the reason for measuring the three-phase resistance balance with a multimeter
The three-phase water pump uses a megohmmeter to measure some leakage. To be precise, it should be shaken with a megohmmeter during a power outage, which means that the insulation is not good. It means that some parts of the cable or the motor are not well insulated from the shell. But there is nothing wrong with the coils of the motor itself. So you use a multimeter to measure the three-phase resistance is good. This is not a contradiction. Find and deal with poor insulation. That's it.
I just talk about the handling method in actual work. Generally, a 500-volt meter is used to measure the insulation resistance of the coil and the shell. There are three results. One is that the resistance is zero. As the saying goes, if the shell is touched, it is grounded. Yes, the motor is broken. The second is that the resistance is infinite, indicating that the motor is good. The third is that there is resistance, which means that there is a problem with the insulation. According to my experience, the insulation resistance is greater than 0.5 megohm. , can also be used, if it is lower than 0.5 megohm, it cannot be used. The second problem is that it is not possible to use a multimeter to measure the balance of three-phase resistance values. The reason is that the inter-turn short circuit of the motor coil cannot be detected. In my experience, even a good motor has different resistance values. Yes, there are some high-power motors with thick coils. The resistance you measured is zero ohms. I know it's not normal.
If you use a megohmmeter to measure the resistance between the three-phase coils when the three-phase coils are not disconnected, it means that you don't understand the common sense of the instrument at all, so don't play, if the megohmmeter is to measure the three-phase coils The resistance between the shell and the shell, the multimeter measures the resistance between the coils, if you measure the situation, it means that the heat of the water pump causes the insulation to age, and the coil winding needs to be replaced! I think you should be in the latter case.
