Electronics > Beginners
Brymen BM235 10A fuse silently destroyed by a switched off UPS leakage current..
hgg:
Its a crappy UPS.
I will use a mains switch for now and I will buy a better UPS with proper isolation.
What is the worst case scenario if the RCD had not tripped?
IanB:
--- Quote from: hgg on March 05, 2019, 06:18:38 pm ---Its a crappy UPS.
I will use a mains switch for now and I will buy a better UPS with proper isolation.
--- End quote ---
I'm not sure why you think a UPS is meant to provide isolation. A UPS is not an isolating device, it is a backup power device. A UPS is meant to be installed and operating 24 hours a day to protect critical equipment that is not meant to be have its power interrupted.
You are using a the UPS in a manner not intended. I do not see why a more expensive UPS will be any different. A good UPS should not even have an on/off switch, since that leaves open the possibility of accidentally interrupting the power to the protected devices.
malagas_on_fire:
The idea of mains switch is to use between the UPS and the Loads you want to disconnect, instead of turning off the UPS. Besides the battery if SLAB or AGM needs maintenace charge to avoid wear over the time
Johnny B Good:
--- Quote from: hgg on March 05, 2019, 05:51:58 pm ---UPS OFF
Ground - Live : 230V
Ground - Neutral : 230V
Live - Neutral : 0V
I've connected an incandescent bulb between live and ground and the house RCD tripped.
The UPS does not isolate mains when switched off but it cannot also power anything from
live to neutral. I have two devices connected. A 3D printer power supply which is earthed
and the Raspberry Pi with its power adapter which is not earthed. The Raspberry power
ON LED switches on and fades off every 5 seconds, only when one of its USB ports is connected
to the grounded 3D printer. So it looks like its a kind of grounding issue.
I think I will include a main power switch as well.
--- End quote ---
That sounds suspiciously like a Y cap issue with the wallwart providing 'half live' leakage current that slowly charges a smoothing cap on the RPi's 5 or 3.3 v rail until there's enough to trigger an on board voltage regulator (buck switching type?) into life to provide a pulse to drive the LED which then discharges the smoothing cap and the cycle repeats over and over (the classic relaxation oscillator effect).
With most (likely all) line interactive UPSes, only the Live output is switched from the incoming mains across to the inverter output. The earth and neutral remain connected with the neutral side of the inverter output bonded to the incoming neutral (which is crossbonded in the mains supply wiring to the earth either at the consumer unit or even as far back as the sub-station (or pole transformer or whatever).
There's normally a 'disable switch' on a UPS so that when the protected load(s) are switched off, you can still keep the battery pack float charged without risking a pointless discharge of the battery in the event of an outage during times when backup power isn't being called for (and also when you want to move the UPS from one location to another or even put it into temporary storage or transport it across town or county from one location to another - longer term storage requires removal/disconnection of the battery pack).
Bearing the fact of the single pole changeover switching in the UPS, it's extremely important that you don't reverse the Live and Neutral connection to the mains supply. The better Line Interactive UPSes actually incorporate mains polarity connection fault detection LEDs to warn of such problems. If you have the Live/neutral reversed, this could readily account for the winking LED via the Y cap in the RPis's smpsu wallwart.
viperidae:
Could be the ups is only switching the neutral line. That would explain the voltages.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version