If you are using them between a DC/DC converter I actually wouldn’t put a breaker in. Any decent DC/DC power supply should be self protecting on the output side. Once they reach rated current they either (a) go into current limit and reduce the voltage until the current drops to the rated limit or (b) shut down completely and try restarting every couple of seconds or (c) shut off (the shitty ones…). If you are powering multiple small loads from the supply you should consider small fuses for each load so that one item failing doesn’t take out the supply for everything.
Mark > On Dec 28, 2018, at 11:26 AM, Jason McKemie > <[email protected]> wrote: > > Thanks everyone. I was a bit confused about the breaker curves as well. > I'm actually using these between a DC/DC converter and the devices being > powered from it. Was hoping to protect the converter in the event of a short > on one of the devices. > > On Friday, December 28, 2018, Ken Hohhof <[email protected] > <mailto:[email protected]>> wrote: > Are you talking the AC or DC voltage rating? DC rating is usually lower, > because it is harder to quench the arc when opening the circuit if the > polarity doesn’t alternate. It’s usually difficult to find breakers with a > DC rating higher than 48 volts. But a higher voltage rating is not a > problem, just may cost a little more. > > > > You also need to look at the trip curve for the family of breakers. The > Altech/Sursum DIN rail breakers I usually use are not technically DC > breakers, but they come in a bazillion different trip curves, I usually buy B > or C. There will be a graph that shows the min/max trip time for various > percent current over rating. Usually that will take care of inrush unless > you have a load that has an unusually large or long lasting inrush. So > something between 1 and 2 times expected load. Let’s face it, if the load is > 1.7 amps, you aren’t going to have a 1.7 amp breaker in your stock of > breakers, maybe you have 2 and 5 amp breakers on hand. In that case I’d > probably go with the 2 amp, because 5 amps may not offer much protection, > especially since you probably have to get to 200% of rating for it to trip > quicky. The exception is any kind of DC UPS that draws extra current when > recharging the batteries, you need to allow for that, or everything will seem > fine until the first time you are recharging the batteries after a power > outage, and the circuit breaker trips after about 30 seconds. > > > > > > From: AF <[email protected] <mailto:[email protected]>> On Behalf > Of Jason McKemie > Sent: Friday, December 28, 2018 9:37 AM > To: AnimalFarm Microwave Users Group <[email protected] > <mailto:[email protected]>> > Subject: [AFMUG] DC Breakers > > > > Do you generally size these about double the expected load? > > > > I see a lot of them rated at higher voltages than I need, will these still be > effective? > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com
-- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com
