What exactly does the AC Hipot test verify, and why is it "destructive" yet indispensable?
The AC Hipot test applies an AC voltage significantly higher than the rated voltage for 60 seconds. It verifies that insulation can survive the worst overvoltage it may encounter in service.
Comparison with other tests:
|
Test |
What It Tells You |
Limitation |
|
IR / PI |
Insulation condition at DC low voltage |
Does not simulate AC stress distribution |
|
Tanδ / PF |
Dielectric loss |
Sensitive to moisture, not gross defects |
|
PD Measurement |
Partial discharge activity |
No pass/fail for total withstand |
|
AC Hipot |
Can it survive worst-case overvoltage? |
Cannot localize defect (pass/fail only) |
The "destructive" nature explained:
• Healthy insulation → passes with no damage (non-destructive to good insulation).
• Weak insulation → breaks down during test (intentional - better in factory than during a storm).
IEC acceptance (IEC 60060-1):
• No disruptive discharge (flashover or breakdown) during the 60-second test.