MOPs of power socket for battery powered device

mr9000

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Hello everyone,

after many hours of searching the internet, this forum, the 60601 and even meetings with consulting firms I feel not wiser, but more confused for the isolation diagramm for our medical device. The main point of confusion is the power socket which charges the internal battery.
So we have an internal battery with up to 8.4V, which can be charged with an external PSU, which is already certified by 60601-1 and outputs 9V. We isolate any conducting surface, in our case only the screws used for mounting the enclosure. So the only point of contact with the internal electrical life is the power socket.
Internally we utilize a piezo motor needing higher voltage, we use custom built transformers for that, the transformers provide 2 mopp between <12V and 170Vp and we will isolate the encoder output from the motor with 2 mopp for 170Vp. So we isolate the high voltage and remain with the battery voltage remaining on our board.
While charging, the plug is inserted into the socket, we have enough CR/AC in this case. The plug has >2mm air clearance providing 2 MOOPs so the conducting parts cannot be reached.
We are stuck with the power socket while the device is battery powered. If we isolate the high voltage and only have 12V (8.4V battery voltage) at the power socket, which is floating and there are no possible other touchable conductive parts, do we need to isolate the power socket by air clearance/creepage distance? Is the isolation needed from conducting parts to the test finger, or is it rather between the conducting parts (plus and minus)?
I stumbled upon 8.4.2.c) and am not sure anymore, especially since it is absolutely not logical to not allow touching of the power socket while the device is internally powered.
I attach our current isolation diagram, which is still a bit wobbly. We'd like to be def-proof, but the increased air clearance and corresponding creepage distance hinder us at the moment because there is no off-the-shelf plug/socket combination where the socket provides such safety distances. The isolation diagram differentiates, if we isolate the 170Vp or try to isolate the 170Vp at the power socket (which would make the internal electrical layout a lot easier).

It would be easier if there would be any SIP/SOPs, but in our case this power socket is the only electrical connection to the outside world.
 

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