IEC 61010, Touch currents related to burns at higher frequencies (cl. 6.3, A.3)

Benjamin Weber

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Dear community,

I am working on touch current measurement acc. IEC 61010 cl. 6.3 and the corresponding annex A.3. The maximum limit value is 500 mA in SFC. THis means, that the maximum power for the actual current measuring resistor R2 in figure A.3 can be as high as 125 W! That is quite a lot. Considering, that the inductance shall be "low", there are not very much components that can be used. Most resistors with this power rating and that are low-/non-inductive are really big and need even bigger heat sinks.

In IEC 60990, annex G.1.2 this high power value is also mentioned, so I am not completely wrong about that. Is there anybody out there, who has experience regarding the following questions:
  1. IEC 61010 only says "high frequencies". Is there any border, whre high frequencies start in this context? If this value is rather low, the other resistor R1 had to be chosen with caution as well.
  2. What are actual touch currents at these high frequencies that occur in the real world? I am thinking about working with a lower value, so that the measuring circuit can built with components with lower power specifications.
  3. We are planning to get accreditation for IEC 61010: Do you think it is possible to exclude the HF touch currents for electrical burns from the accreditation scope or would this mean, that we cannot test acc. 61010 at all? In my opinion this test is only appplicable for devices, that actually are able to delver such high currents at accessible parts. And I think, this would be only a a asmall amount of the devices we are aiming at (mostly IVDs and similar).
I would be really really happy, if anybody could help me here!
 
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