Use a multimeter to measure the ohm level. If normal, use a megger to show a short circuit.
As we all know, submersible pumps are prone to water intrusion due to wear of seals during use. The degree of insulation will be reduced when water enters.
It is not possible to use a megger to measure the insulation of a submersible pump that is filled with water. Because the voltage of the megger is relatively high, such as 500Ⅴ, 1000Ⅴ, 1500Ⅴ, 2000Ⅴ, etc., sometimes the submersible pump only receives water, but the insulation level is reduced, and the insulation is not damaged. If you use a megger to measure the insulation at this time, it is very likely to cause insulation breakdown to ground, between phases, and between turns.
The voltage of the meter used is very low, and the submersible pump used to measure the incoming water is well insulated. At this time, the submersible pump can be opened for drying. At the same time, the sealing elements must be replaced.
After drying, a 500V megger can be used to test the insulation.
Shake slowly first and then measure at a speed of 120 revolutions per minute. (The insulation between ground and phase should be above 0.5 megohm before use.
The reason is very simple. The potential of the multimeter is small and the measuring unit of the megohmmeter is too large. The megohmmeter is also called a megohmmeter. In terms of megohms, the resistance of the water pump is not that large. In the megohms unit, it can be ignored at all, so see It's a short circuit, but it can't be detected.
1: You want to measure the insulation resistance
2: Ordinary multimeters can only measure the on-off resistance of the water pump coil, but cannot measure the insulation resistance of the shell.
3: Insulation resistance needs to be measured with a megger.
4: The essential difference between the two is that the working voltage is different
The hand-operated generator inside the megohmmeter generates 500v or 1000v voltage to measure the insulation breakdown voltage.
The working voltage of an ordinary multimeter is 9V
It is normal to use a multimeter to measure the water pump ground short circuit problem because the main function of the multimeter is to measure continuity, and it is not suitable for measuring insulation resistance, because the multimeter measures a low voltage of up to 9V while the common voltage is very large, ranging from several thousand ohms to tens of megohms. The measured current is almost zero so it cannot be measured accurately. The megometer generally uses 5oov to measure the insulation resistance (low-voltage circuits, electrical appliances) more accurately.
The multimeter can only measure the resistance value of several thousand ohms. For the insulation resistance, it should be several megohms. The multimeter can only test the insulation resistance under low DC voltage. The megohmmeter will use a voltage higher than normal use to test. Many Under normal circumstances, low voltage will not cause leakage, and high voltage will show leakage. To detect the quality of electromechanical equipment, a megohmmeter is a special instrument.
