Why is the water pump short-circuited with a multimeter to measure ohms with a vibration table?
It is well known that submersible pumps are prone to water ingress due to wear and tear of seals during use. The degree of insulation will be reduced after water ingress.
Submersible pumps into the water can not be insulated with a shaking table. Because of the higher voltage of the swing meter, 500 Ⅴ, 1000 Ⅴ, 1500 Ⅴ, 2000 Ⅴ, etc., sometimes the submersible pump just into the water, but the degree of insulation is reduced, the insulation and not be bad. If this time with a swing meter to measure its insulation, it is likely to cause the ground, phase to phase, turn to turn insulation breakdown.
Square meter voltage is very low, measured into the water submersible pump insulation is very good, at this time you can open the submersible pump for drying treatment. At the same time to replace the sealing elements.
After drying can be used 500 Ⅴ shaking table to measure its insulation.
First slow shake and then in the speed of 120 revolutions per minute to measure, (ground insulation, phase-to-phase insulation should be 0.5 megohms or more can be used.
The reason is very simple ah, the multimeter potential is small, shaking table measurement unit is too large, shaking table and called megohm table, on megohm, the pump resistance is not so large, in megohm units, simply negligible, so it looks like a short-circuit, in fact, is not measured.
1: you want to measure insulation resistance
2: ordinary multimeter can only measure the pump coil on-off resistance, can not measure the insulation resistance to the shell, the
3: insulation resistance needs to be measured with megohmmeter.
4: the essential difference between the two is the different working voltage
Megohmmeter internal hand-cranked generator generates 500v or 1000v voltage, as the measurement of insulation breakdown voltage.
Ordinary multimeter working voltage is 9V.
Pump grounded short-circuit problem with the multimeter measurement is normal, because the main function of the multimeter is to measure the through, for the measurement of insulation resistance is not appropriate, because the multimeter measurement voltage is low up to 9V and the united edge of the electric but very large, such as a few thousand ohms to dozens of megohms to measure the current is almost zero, so it can not be measured accurately. Rocking table generally 5oov measurement (low-voltage circuits, electrical appliances) insulation resistance is more accurate.
Multimeter can only energy out of a few thousand ohms of resistance, for insulation resistance, should be in a few megohms, multimeter it can only test low DC voltage insulation resistance, megohmmeter will be higher than the normal use of the voltage to test, in many cases, the low voltage will not leakage, the voltage is high in order to show the leakage. Detect the good and bad electromechanical, megohmmeter is a special instrument.
