I was wondering about digital isolators. I have some temperature sensors installed inside the windings of a 6.6kV motor. I would like for my system to not be completely destroyed in case of a short.
For instance, the Si86xxT isolators from Silicon Labs. They offer 5kVrms isolation for up to 1 second.
But how about clearance between the uncoated pads/leads? According to this calculator I have seen used in other answers, about 33mm of clearance between the pins is needed. But the wide body package of the Si86xxT devices do not even offer half that (~7.5mm).
How do you protect your device for longer than 1 second? I had thought about fuses on both input lines but this does not sound ideal, you can't be sure the fuses would blow fast enough.
How can they claim such a high isolation voltage if the clearance is not large enough?
Best Answer
Take a look at UL60950 norm.
There's a table that answers your question.
Clearance depends also on the pollution class of the environment where your board will work in.
There are 3 classes, where 3 is the most polluted environment.