If you think that the spike from killing the power by dropping the contactor will kill your electronics, then you can design a circuit that protects against that. Even thoug the current is high, it will not last long so while the instantaneous power might easily kill sensitive electronics, the total energy that you need to dissipate is not very high. Well-chosen Gas Discharge Tube or snubber circuits can probably take care of protecting your downstream electronics from the effect of sudden interrupted contactor. Of course, the contactor itself will not survive repeated interruptions under power, so by definition it should be a rare occasion that you drop the contactors anyway.
Regards, Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of corbin dunn Sent: Monday, February 25, 2013 7:51 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Inertia switch On Feb 25, 2013, at 3:24 PM, Lee Hart <[email protected]> wrote: >>>> Typical way to use [the inertia switch] is to wire it in the >>>> circuit that engages the pack contactor coil (so, a 12V circuit). >>>> If the switch opens after an accident, the high voltage from the >>>> pack is interrupted because the contactor(s) drop out. > > Steve Clunn<[email protected]> wrote: >>> Some controllers and most contactors aren't happy being opened under >>> load. > > Things obviously last longer when *not* asked to break high current. > However, it is sometimes necessary to do it anyway (such as in an > accident, or to stop a runaway controller). > > corbin dunn wrote: >> Really? which ones? Most should handle this okay. I know the Netgain >> brand controllers are fine. > > It isn't brand-specific; it is circumstance-specific. > > Most controller skimp on the size of their input capacitors. They depend on the battery to handle at least some of the inductive energy that "kicks" the voltage up when the controller shuts off. > > If the controller is operating at high current, and the battery suddenly goes away, the voltage on the capacitors and transistors will spike up much higher than normal. If the EV has a large design margin (like 250v parts with a 150v pack), it will survive. But if the controller has 200v parts and the pack is 144v (and at 180v because it was just charged), there is not enough safety margin and the controller can blow. > >>> I've been hooking the Inertia switch to turn off the key input to >>> controller. > >> I think that defeats the purpose of the inertia switch. > > The inertia switch is supposed to *absolutely* shut things down in case of an accident. But one possible reason for an accident can be a runaway controller! So, it is best if the inertia switch shuts everything off that it can (controller *and* contactors). Good point! I should have been more clear: I have mine wired up in exactly this way. The switch cuts off the 12v key-on input into the controller, and the 12v power into one contactor. corbin > > -- > *BE* the change that you wish to see in the world. -- Mahatma Gandhi > -- > Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.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) _______________________________________________ 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)
