I have been following this for several days. The concern about a DC high current circuit breaker is the maximum interrupting current at the operating voltage. If a fault or a turn off happens under load there will be an arc. The speed the contacts open, possibly a magnetic arc deflector all determine if the arc will maintain or be broken. If it is maintained the circuit is still closed by plasma inside the breaker. If the short circuit current of you battery system is less than the maximum interrupting current the breaker, preferably less than half, and the nominal voltage is under the breakers rating it is properly applied. Unlike a relay, there is a lot of opening and closing force in a circuit breaker and they are designed to protect the circuit even if they are destroyed. Always remember Murphy's Law: A fuse will only protect something only if the fuse costs more than what it protects. David Kerzel
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of J Bills Sent: Wednesday, June 26, 2013 6:10 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Airpax ALM-250 safe on 160V system? to add to this (since I've been there) - That circuit breaker works fine for my 156v DC system, but your AC system is very different and looks like it would be producing higher peaks than I what I put through it. i should say, I have the JLE-1-1-53-B4-250 But I did email Airpax (which is really Sensata Technologies) to make sure it could handle what I was putting through it, since nominally I'm under the 160 but we all know that in reality, a nominal 156v pack of AGMs can see voltages up in the 170+ range. They said the rating is a standard one and that it should be fine for another 10% or so as long as there isn't an overly high short circuit current at the peak voltage. In my case, as best as I can tell I'm probably fine, and the contacts shouldn't be in danger of welding. just kind of restating what lee was explaining but using my setup. If you run the numbers as best you can and are still in doubt, you could email the tech support at Sensata - I found them very knowledgeable and responsive, which is great when you don't know all the specs and limits. because they do! On Tue, Jun 25, 2013 at 10:26 AM, Lee Hart <[email protected]> wrote: > Mike Scott wrote: > >> I'd like to use this breaker I have, but now have 50 LiFePo calls >> instead of the 12 12V gels. Is it time to break out the spare breaker >> and wire them in series? >> >> The rating says "Max 160V", but charging will go above that. >> > > The circuit breaker's 160v rating isn't absolute. The complete rating > would be something like "can safely interrupt 160vdc at 10,000 amps > with a resistive load ONE TIME". > > Sometimes the manufacturer gives a set of curves, showing the safe > interrupting voltage at different currents, and with different kinds > of loads. If the current is lower, the voltage it can safety interrupt > goes up. If the load is worse (inductive), then it goes down. In your > case, I doubt that the load will be inductive. Both the batteries and > the charger will appear as capacitive loads. > > Assuming that your circuit breaker is built similar to others that > *do* have these full ratings, I would expect it to behave something like this: > > 160vdc at 10,000 amps resistive > 250vdc at 1,000 amps resistive > 350vdc at 100 amps resistive > > Thus, you can probably use it at 250vdc in a circuit that can't > produce a fault current over 1000 amps. A worst-case failure in your > charger is unlikely to be able to draw this much current, so it should be safe. > > The more serious question is: If the charger does fail (shorted output > capacitor or rectifier), it may draw 100 amps, which is NOT enough to > trip that breaker! So it is important to have a fuse in the charger > output so something WILL blow to stop the current. Otherwise, you can > get one heck of a fire if the charger fails and the batteries dump > 160vdc at 100 amps back into it! > -- > For every complex problem, there is a solution that is simple, > obvious, and wrong. -- H.L. Mencken > -- > Lee A. Hart, > http://www.sunrise-ev.com/**LeesEVs.htm<http://www.sunrise-ev.com/Lees > EVs.htm> > > ______________________________**_________________ > UNSUBSCRIBE: > http://www.evdl.org/help/**index.html#usub<http://www.evdl.org/help/in > dex.html#usub> > http://lists.evdl.org/**listinfo.cgi/ev-evdl.org<http://lists.evdl.org > /listinfo.cgi/ev-evdl.org> For EV drag racing discussion, please use > NEDRA (http://groups.yahoo.com/* *group/NEDRA > <http://groups.yahoo.com/group/NEDRA>) > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130626/5985da1c /attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
