I don't have an inertia switch, but I have had the IGBT of my controller go short-circuit, which would cause a run-away situation, if not for the controller monitoring the current and simply dropping the contactor when it noticed that the current was above the critical threshold, so all I noticed of the IGBT failing was a short clunk in the drivetrain and the power dropping out. The controller also protected from starting again, because it monitors the controller output *before* closing contactors through a high resistance voltage divider. If the output of the controller (with the motor contactor unengaged) is not near half the pack voltage then it assumes that either the transistor or the freewheel diode is shorted, or another reason that the output is not floating, such as a defective snubber and it will not close the contactor, only throw an error code. Very useful. Thanks, Rod! 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 Lee Hart Sent: Monday, February 25, 2013 3:25 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Inertia switch >>> 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). -- *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)
