| Electronics > Beginners |
| Brymen BM235 10A fuse silently destroyed by a switched off UPS leakage current.. |
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| hgg:
--- Quote from: IanB on March 05, 2019, 07:02:23 pm --- . 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. --- End quote --- Exactly, especially when it has one and does nothing... It gives you a false sense of security when it just isolates between live and neutral. They should have at least put a huge sticker on it with a warning. I've just checked my UPS on my main computer which is a much more expensive unit with a pure sinewave output and when you switch it off you have proper isolation from the mains. Its off. You have to press the power off button for at least 20 seconds in order to switch it off, so you can not turn it off by accident. |
| hgg:
Johnny B Good: " 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." YES, YES! That was the problem. I reversed the mains plug on the wall and everything works fine now. No mains output when switched off and no blinking LED on the Raspberry Pi. Thank you!! They should specifically mention that this UPS needs a proper live/neutral wiring! |
| malagas_on_fire:
Normally that feature is on the manual of the UPS or in the low end model of some know brands, eg, APC surge outlets with small batteries: https://www.apc.com/kh/en/faqs/FA158817/ |
| johnkenyon:
--- Quote from: Johnny B Good on March 06, 2019, 02:06:54 am --- 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. --- End quote --- Easily retrofittable - wire a red mains neon indicator (with integral resistor) between the incoming neutral and ground., and mount it on the rear or front panel, labelled "L-N reversed" or "P-N reversed" |
| hgg:
Not a bad idea at all. I think I will do it. Problem Solved. One question remains though! When I connected the 40 watt light bulb from live to ground the RCD tripped immediately. When I connected the BM235 the fuse blew before the RCD had the chance to trip. The RCD needs less than 30mA to trip, usually 25 to 28 if its in a good condition. So the fuse blew with 230V and less than 30mA for a few milliseconds. Does this make any sense? Was the fuse faulty or is there something I do not understand? (probably.. :) ) |
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