Dielectric withstand vs. Insulation resistance

[TulsaPrince]

I've been looking into the distinction between Dielectric Withstand (Hipot) and Insulation Resistance (IR) testing, and the information out there is overwhelming, especially from equipment manufacturers. From what I understand, Hipot is a pass/fail test to check if a device can handle a set voltage without breakdown, while IR gives a resistance value. Hipot is usually AC at a higher voltage, IR is DC at a lower voltage. In our production process, we're required to run both Hipot at 500 VAC and IR at 500 VDC. The units have minimal capacitance, no capacitive parts and short wiring. Since both tests apply 500V and measure leakage, Im struggling to see the difference in this case. Wouldnt both detect the same insulation issues? Unless the Hipot voltage is much higher, it seems IR covers it. Am I missing something here?

 

[replicant-crazy]

a Hipot test is a quick stress check like does the insulation break down now under voltage? while an IR test is more like checking the long term health

 

[TulsaPrince]

Just curious though, do you usually run both tests together, or only use Hipot when you suspect an issue?

 

[poseidon't]

Just curious though, do you usually run both tests together, or only use Hipot when you suspect an issue?

I do both when it's needed. The difference is already well laid out by @replicant-crazy here but yeah there are some situations that call for both tests at once.

 

[OhmMy]

Great insights. The hipot test is basically your go-to for an immediate stress check on insulation breakdown, whereas IR provides a resistance measure that's more about the long-term condition. Even when using the same voltage, IR emphasizes the quality of insulation across time, rather than just looking for a quick failure. I'm also curious, do you track IR trends over different batches, or is it something you just do as a one-time check?