Current Limit in IEC 60601 Dielectric Strength Testing

[Riskcord]

Hi everybody,

I have a short question regarding dielectric strenght testing. The 3rd edition specifies a fail criteria for dielectric strenght in 8.8.3.b as follows:

During the test, breakdown constitutes a failure. Insulation breakdown is considered to have occurred when the current which flows as a result of the application of the test voltage rapidly increases in an uncontrolled manner, that is, the insulation does not restrict the flow of the current.

Here, no specific limit is provided for the dielectric current. I have been told by an UL engineer that in the second edition there was a specification for a limit value for the dielectric current. I havent been able to find it though.

Does anybody know anything about this? Maybe in a different standard?

Thanks guys and have a good day!

Pablo

 

[Peter Selvey]

Other IEC standards have (or had) a 100mA limit for the insulation tester (per memory, at least the IEC 60335 series), however this was never put in IEC 60601-1. So it's just strongly recommended.

The theory is that if the tester does not have enough current, when a partial breakdown occurs the voltage drops and the insulation recovers. This means the tester's current capacity (not the current limit) can affect a pass/fail result.