Hi Justin, My guess is that the minimum voltage requirement is because a circuit breaker needs a minimum amount of power to move the mechanism. You are correct that voltage has nothing to do with initiating the trip event, but it probably has a lot to do with completing it. Assuming that it is a thermal CB, the over current you caused was enough to make the bi-metal strip bend part-way but then the breaker is probably designed to increase in resistance slightly and heat the strip more abruptly to force the contacts open. Sean On Mon, Sep 10, 2012 at 5:25 AM, Justin Richards wrote: > Just did some additional testing as I figured the device is probably > no good anyway but found that at 2A it takes approx 80 secs to fail. > > It does get hot and does smell but does still trip. > > What else has surprised me is at the rated current of 1A it drops 1.5 > volts and at 2 A it drops 3 amps. Tested a standard barrel type 15A > glass fuse and it drops approx 0 volts at 2 amps. > > I have left it on with 1A and by the datasheet it should run > indefinitely. Will see how it goes. > > The datasheet also states a minimum of 12V DC but this seems strange > as the breaker will never see such a volt drop while it is in the > un-tripped state. > > Why is there a need for a minimum voltage. > > > > On 10 September 2012 17:04, Justin Richards w= rote: >> Purchased 1A circuit breakers to install at a remote solar powered >> WIFI access point. >> >> Received from RS a ABB S201MC1 type C 10kA single pole stock number 539= -1553. >> >> The catalog quotes Max operating voltage 440Vac, 60Vdc. >> >> There has been some discussion amongst peers that there are DC and AC >> type circuit breakers. >> >> I accepted this and looking for a suitable part discovered some have a >> AC and DC rating others just have a AC rating. >> >> Curious, I hooked this up to a bench power supply expecting it to trip >> at approx 1A, but nothing until approx 7A where it got hot and finally >> tripped. The CB now has a distinct burnt smell. >> >> Remember back to my electronics education I remember asking about >> fuses and being told that it is the current that trips them. I >> commented on the fact that I have seen 240v X amp fuses used in >> vehicles for example. I was told the 240V was simply what it was >> rated at which made sense because they dont really have 240 across >> them until they have done the job they were designed for. >> >> A discussion on the PICLIST recently, encouraged me to install CB's >> and further helped explain the ins and out of CB. >> >> I noted that the volts reading on the bench supply was low and went up >> to about 6v before the CB tripped. And expect the volt drop across >> the CB would have been even lower but the current was well over 1A. I >> set it to 2A and left it for a few seconds as they are designed for >> high inrush currents. >> >> But 7A for perhaps 10 secs and a burnt smell doesnt really seem to me >> that the CB is doing its job. >> >> They were the only CB's I could find in the catalog that went as low >> as 1A, had a DC voltage rating and offered DIN rail mouting. >> >> It appears that these are not designed for DC even though there is no >> indication to that effect. >> >> The tripping curve from >> http://www.clrwtr.com/PDF/ABB-Controls/ABB-S200-Miniature-Circuit-Breake= rs.pdf >> indicates that the type C may trip from 5 - 18 times the rated current >> for up to 1 sec. The tripping curve then extends further indicating >> lower trip currents for longer periods of time for example twice the >> tripping current for approx 50 secs. >> >> This fits with my experiment but I was not expecting the CB to give >> off the horrible smell. >> >> Anyone experimented wit these. >> >> Cheers Justin > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .