So a while ago i got my hands on a old sewing machine sadly the foot pedal blew up on me and i also noticed that the machine made my fingers tingle (more on that in this old post here: https://sh.itjust.works/post/35395330 ).
After that i didnt touch the thing for a while but now i needed to sew something so i got myself a new motor and pedal for it online.
The motor fits neat to the machine and the pedal works. But after the last time i was a bit afraid to just touch it, decided to better do a voltage check first.
So i grabbed a Multi meter and connected one side to main earth, and the other side to the metal body of the machine.
And apparently there are 30-32V AC on the metal body of the machine :( Then i tested the current and it was 4.1uA.
I did the same thing for the motor spindle an and the results where even worse >.< 173V AC on the spindle and 43uA when i short it to main earth over the multi meter.
Now my question is:
Is this normal?
Is it maybe just some parasitic currents from the Motor windings acting as antenna and inducting voltage into the metal body of the machine?
Will it kill me if i touch it?
Should i ground the machine to earth using a second plug?
Should i isolate the motor from the metal machine body?
Here are some more pictures from my measurements and measurement setup:
What would speak against the second plug solution (besides it beeing anoying)?
It's just safer, makes it impossible for the chassis to be un-grounded while the machine is powered. Doesn't really matter if you're the only one using the machine and trust yourself to always remember to check if it's pluged in.
I think this is rather unlikely to happen, but I should mention it:
There's also some potential to create objectionable current, since neutral is already bonded to earth. And if the PE is pluged into a into a different outlet (or somehow else has a diffrent path to earth), you create parallel paths. There would be small diffreneces between those paths in resistance (and voltage). That means a tiny current can circulate between them, instead of going through the intended ground path.
Those currents should be small, simillar to what you already measured, but they create unpredictability (edit: worded this wrong, they don't create unpredictability but rather are a sign of it, the unpredictability is caused by the closed loop to ground). If a real fault happens it could make the fault current split changing how a breaker responds. Also, if you have audio equipment, and the objectionable current path goes through it's ground path you could get some noise/humming