Electronics > Beginners

Brymen BM235 10A fuse silently destroyed by a switched off UPS leakage current..

(1/12) > >>

hgg:
Hi,

I have a Raspberry Pi plugged in a UPS which I switch off when not used.
Recently I've noticed that the power on led of the Raspberry blinks and fades
away every 5 seconds with the UPS switched off.

I measured ground to live and ground to neutral on the UPS output socket
and they show 229V!..   

Is this normal?
Should I throw the UPS in the bin?
When I switch on the UPS the connected devices work normally.



I've tried to measure any leakage current to ground and the BM235 showed nothing, instead it
started showing 'DIODE' when I connect the leads..   I took off the 10A fuse and it shows no continuity!
Like its damaged. I doubt that more than 10A passed from live to ground on a switched off UPS.
The fuse looks new, no explosion were heard, no sparks were seen.   :)

How is this possible ?   :-//






Thanks.

Cnoob:
You UPS may have your neutral isolated from your earth unlike true mains mine reads 247VAC between Live and Earth and 1.8VAC between Neutral and Earth which is a ghost voltage (induced Voltage).
As for anything wrong with your UPS I don't much about them but it doesn't surprise me you are reading mains level voltages between your earth live and neutral.

But your RPI is connected to your UPS by a USB connection and that's where your fault could be. leaky  capacitors seem to cause problems a lot more now.

As for your Meter, They don't have a manual on TME and my BM257 manual doesn't say anything about blown fuse indication, but I am going to take the fuse out of it and connect it inline in a circuit.

Cnoob:
I took the out the 11amp HRC fuse the meters display read zero amps or as good as damm it.
So I took the 400milli Amp HRC set the meter on milli amp range and plugged lead in Milli/micro circuit back on
still read zero current flowing.

It could be a feature of your meter or something is wrong.

hgg:
The Raspberry Pi 3 is connected to the mains output of the UPS with its own power adaptor. 
Its not connected via USB.

The fuse does not show any continuity.  Its toast.
I am at a loss how this fuse got damaged by connecting it from live to ground of the UPS !!

Cnoob:
First off then your power adaptor is at fault.
Second if you connected Live to ground/earth with your meter set and connected to measure current  (Amps) then you shorted it and that would cause the fuse to blow. But If you were measuring voltages then it would not be the cause of your 11 amp fuse to blow.

It isn't unknow that fuse just seem to go open circuit without a specific cause.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod