110V DC Floating Earth Ground Fault

[BenM_Uk]

Good morning all,

I have found this forum while searching for clues on a ground fault.

A 'ground fault' alarm came in over the weekend on the 110V charging system. We have two 110V fans currently running and I am suspecting that one is at fault but I can't turn it off yet to fault find. I say I suspect this as we have had to change them before because of low insulation resistance to earth. The motors are on a 3 wire DC system.

The measured voltage to earth on the running motors is
A - Earth 76V
AZ - Earth -44V

The output voltage is currently around 121-123V DC.

Now the strange thing for me is that when i turned on the 110V DC lights that run off the same batteries, the fault clears.

I then measured the voltage again at the motors and got the following

A - Earth -44V
AZ - Earth 76V

I am not 100% clued up on DC floating earth systems. If anyone can help educate me I'd appreciate it.

Ben

 

[BenM_Uk]

Sorted - I was drawn too much towards the motors due to past issues.

Ended up disconnecting one of the lighting circuits and all is well

 

[itsmoked]

Good on you! Thanks for coming back on the find.

Keith Cress
kcress -

http://www.flaminsystems.com