I should have put a smiley face after my comment; it was meant to be a joke. Guess I'd better stop planning for that future career as a comedy writer. :)
Sorry for the confusion, Bill -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Cor van de Water Sent: Thursday, April 11, 2013 1:20 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Reversing Contactors Yet Again You are thinking about the coil of the contactor, which typically has an anti-parallel diode or surge suppressor to catch the high voltage kick-back when the power to the coil is interrupted - you do not want to blow the switching transistor when it tries to turn off the contactor (it might fail shorted and cause the contactor to stay on, defeating the purpose). Lee is talking about the switching arrangement of the contacts to achieve reversing of a DC motor. Since the common setup is to use two single contact units to reverse the motor, you have some choices how to wire the contacts. - you can connect the center contacts to the supply (controller) side and connect the motor leads to the NO and NC contacts, but this has the drawback that when one contactor switches faster than the other, it will short the controller. - you can connect the center contacts to the two motor leads and connect the controller between the NO and NC contacts. That way, if one contactor switches before the other, it will short the motor but not the controller. Lee remarked that if you short the armature of a running motor with magnetised field, then you get unpredictable currents, you lock up the motor and since this typically is a direct drive situation, you may cause the EV to lock the wheels, skid and get into a crash. Better to switch the field, because a collapsing field does not result in the same magnitude of problems. BTW, "SNORT" is a known word, typically referring to forceful inhaling, but it has also been used to name a tool that captures large amounts of data from wireless networks (either to try to catch sensitive information that could lead to finding security keys of a network or to defend the network by detecting unauthorized transmissions). It is a software hacking tool. http://www.snort.org/ 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 Bill Dennis Sent: Thursday, April 11, 2013 8:58 AM To: 'Electric Vehicle Discussion List' Subject: Re: [EVDL] Reversing Contactors Yet Again I always thought it was the freewheel diode that snorts the magnetic field. Bill -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Rod Hower Sent: Thursday, April 11, 2013 9:00 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Reversing Contactors Yet Again Lee Hart wrote: >> a reversing contactor typically *snorts* the field Brings back memories of Bob Rice. I kind of like the new description! ----- Original Message ---- From: Lee Hart <[email protected]> To: Electric Vehicle Discussion List <[email protected]> Sent: Wed, April 10, 2013 11:31:18 PM Subject: Re: [EVDL] Reversing Contactors Yet Again Lee Hart wrote: >> a reversing contactor typically *snorts* the field Paul Wujek wrote: > I hope you meant *shorts* or there is a term I have not heard of before. Ooh, that's a good one! Don't you just love it when the spell checker has a sense of humor. :-) -- The principal defect in a storage battery is its modesty. It does not spark, creak, groan, nor slow down under overload. It does not rotate. It works where it is, and will silently work up to the point of destruction without making any audible or visible signs of distress. -- Electrical Review, 1902 -- 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) _______________________________________________ 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)
