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High Voltage Capacitor Testing.


New Member
How can I test these caps?Can I use a Megger /Insulation Tester ? Can this cap be charged by the Insulation Tester to 4000 Vdc and then read the resistance to calculate leakage current?I have a Digital Insulation tester that does AUTOMATIC DISCHARGE,will It damage the tester?OR any advise on how to perform a test on these caps.Thank you.


Well-Known Member
Most Helpful Member
have you tried using an ohmmeter, the fluke series of DVMs are good
But they apply less than 5V to the capacitor when testing leakage in the auto-ranging "Ohms" position. Mariusmul is concerned about how much leakage his capacitors have when they are charged to 4000V.


Well-Known Member
Most Helpful Member
yeah, you need a real cap leakage tester for those. i don't even think a Sencore goes up that high... if you know what you are doing, you can make a voltage multiplier to take some low current high voltage AC and put it through the multiplier to get 4kv, then connect the cap across it with a 1 meg resistor in series on the ground side. every volt across the 1 meg resistor is a microamp of leakage. since most DMMs these days are isolated to 600-1kV, you will need a voltage divider across the output of the multiplier to measure it.


New Member
Before testing a capacitor verify the cap is discharged if not discharge it through a some KOhms
resistor first and then shorting the two wires, above all do not sshort the two wires first( because
the spark may be occuring inside the cap and now your cap is probably FNG) instead between wires. That's the rule I learned at the
begining of my career long time ago...
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