What is the reason for the balance of three-phase resistance measured with a multimeter
Three-phase water pump with megohmmeter measurement of some leakage, exactly should be the case of power outage, with megohmmeter shaking, that is to say, bad insulation. It means that the cable or the motor, some parts of the insulation is not good with the shell. But there is nothing wrong with the coil of the motor itself. So you measure the three-phase resistance with a multimeter is good. This is not a contradiction. Find the place with bad insulation and deal with it. It will be fine.
I only say that in the actual work of the processing method, in general, with a 500-volt shaking table to measure the insulation resistance of the coil and the shell, there are three kinds of results, one kind of resistance is zero, we say in common parlance that touches the shell is also grounded, the motor is bad, the second kind of resistance is infinite, indicating that the motor is good, and the third kind of situation is that there is a resistance, which indicates that there is a problem with the insulation, according to my experience, the insulation resistance is greater than 0.5 megohm case, can still be used, less than 0.5 megohm can not be used. The second problem is to use a multimeter to measure the three-phase resistance balance, is not possible, the reason is that the motor coil turns short circuit is not measured, in my experience, both is a good motor, the resistance value is not exactly the same, there are some power motor, coil is very thick, you measure the resistance value is zero ohms, which is even more unable to illustrate the problem, look at the three-phase balance can only be the motor startup and operation, and take the card table card three-phase current, you will know normal or not. Know normal or not.
If you do not disconnect the three-phase coil with megohmmeter to measure the resistance between the three-phase coil, showing that you do not understand the common sense of the instrument, or do not play, if the megohmmeter is to measure the resistance between the three-phase coil and the shell, the multimeter to measure the resistance between the coils, such as you measure the case of the pump heat caused by the insulation deterioration, the need to replace the coil windings! I think you would be in the latter situation.
