Hi Michael, If you mean whether I removed the second of the 3 legs of the "E" to make a "C" shape core, no - I had not thought of that. That would indeed open up a much bigger hole for winding than that I used. I believe that my motor cabling is 0000, seeing that I could barely fit 3 windings in the two slots of the "E" and still get the "I" back on.
Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: cwa...@proxim.com Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Michael K Johnson via EV Sent: Monday, August 11, 2014 6:47 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Protecting DC PWM Controller from lowinductance/resistancemotors Cor, How many turns did you wind? I'm assuming you removed the center portion of the EI in order to get a rectangular shape? Adam, Check http://www.geepglobal.com/locations/usa/north-carolina/ if you don't find anything high-power on craigslist. I suppose if you need more room for wire you could get two and discard the I sections as well as the center bars of the E sections and hold them together with the openings facing each other... On Mon, Aug 11, 2014 at 5:51 PM, Cor van de Water via EV <ev@lists.evdl.org> wrote: > Adam, > I added a (free) inductor by wrapping the motor wires around the core of > the biggest microwave transformer that I could find. > You can pick up old microwaves most days from Craigslist and the like > for free. I occasionally get one, disassemble it if I can't get it to > work to give to a needy friend, so I have a stash of components to fix > the next one. > Note that it is required to put a very thin spacer between the two core > halves to avoid saturation and you need something (I used a very large > hose clamp plus 1 or 2 steel wires cross-wise along the core) to keep > the two halves together and aligned. > > Cor van de Water > Chief Scientist > Proxim Wireless Corporation http://www.proxim.com > Email: cwa...@proxim.com Private: http://www.cvandewater.info > Skype: cor_van_de_water Tel: +1 408 383 7626 > > > -----Original Message----- > From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Adam Chasen via > EV > Sent: Monday, August 11, 2014 2:16 PM > To: ev@lists.evdl.org > Subject: [EVDL] Protecting DC PWM Controller from low > inductance/resistancemotors > > I recently purchased a 1980 Lectric Leopard (Renault 5 "Le Car" > http://www.evalbum.com/190) with the following specifications: > > * original Presolite 6.7"(?) series wound DC motor (presumably advanced > for > higher voltages) > > * 16kWh LiPo NMC packs in 24s4p arrangement for 90V nominal with 150A > semiconductor on each of the 4 packs > > * Curtis 1231C controller with PB-6 > > 2 weeks ago I heard a loud pop as I depressed the throttle out of a > rolling > stop/turn and my voltmeter read 0. Seemed like my semiconductor fuses > did > the job and all 4 were popped ($100 worth of fuses mind you). > Unfortunately in my distressed mindset I bypassed the fuse on one pack > and > the car lurched a few inches as soon as I flipped my breaker and then > stopped (I know, bad call). > > I disassembled the Curtis controller and discovered 2 "gently" blown > mosfets and 1 "catastrophic" mosfet failure. I ordered replacement > mosfets > IXTH50N20. One trace on the power board looks like it overheated and > there > appears to be some damage (a resistor?) on the control board. There is > possibly damage to a trace in an internal layer, but not sure if it is a > 2 > layer board and some surface heating caused some damage. > > I have since swapped the Curtis out for a 750A Logisystems which I am > aware > are plagued with (similar?) issues. These failures appear to be due to > low > resistance/low inductance motors causing a overcurrent condition. The > logisystems doesn't provide for a 1.5kHz during startup. That is a bit > concerning as that was the "workaround" for the Curtis. > > I have since measured the motor side of the controller with an inrush > current sensor and measured 645A max even with being very careful to > slowly > depress the throttle. > > My concern centers around this happening again, especially on my larger > 1989 BWM 535i with a directly coupled FB1-4001a motor. There are a few > proposed solutions I read about and a few I came up with on my own which > I > am soliciting opinions on. > > A big unknown to me is how much resistance or inductance needs to be > introduced to prevent this kind of inrush/runaway. > > One solution is to use the clutch in the Leopard to ensure there is no > starting load on the motor. I still measured inrushes of >300A with no > load! That will not work for my directly coupled 1989 BMW. I am curious > if > Lee Hart (with his Leopard) and others with series wound DC motors drive > using the clutch. I have since modified my shifting behavior to much > higher > RPMs after reading some about his driving style. > > Another is to control the current with a large inductor. There was a lot > of > talk, but no pictures of these inductors. I am not sure how much > inductance > is necessary to help, but haven't done much research into this. There > was > some mention of using surplus transformers with insulated layers, but > wasn't able to get a good picture in my head of size and process. > Someone > mentioned a 30 lbs choke on an older PMC, but that also doesn't provide > me > a good picture in my head other than it will likely be bigger than any > non-power system transformer I have ever seen. Where can I get one (or > the > materials for) of these inductors and how much will the cost? > > There are two other passive electronic components which can control > current > I didn't see mentioned. > > * Resistors > > * Thermistor > > I am not sure about the practicality of using a thermistor for this > purpose. It would appear the PTC thermistor would effectively be a > self-resetting fuse. Ideally I could find a thermistor which would only > increase in resistance to the point where the motor still received > current, > but provided some restriction. It appears they are mostly sold as > "switches" due to their non-linear response. I am also unsure if the > response time will be of any use. I would much prefer something more > linear. > > Using an NTC thermistor (or bank of them) would provide a tiny > resistance > to start with but would "close" very quickly. My guess is that it would > not > provide the necessary protection. > > Introducing a fixed resistor would introduce a loss in the system which > is > not desirable, but it could be as simple as just the resistance of the > feed > wire. The thought would be to reduce the size of the cable (or a portion > of > the cable) to the point where it begins acting as a resistor (i.e. > heating > element) as high currents pass through it. I am not an EE, so I don't > understand exactly the nuances of high currents through wire. It would > seem > cables do not have a linear resistance. Once again, I am unsure of how > practical this is or what resistance is necessary. > > There is also an option for a combination of these two passive > components > which would slow down the NTC. The motor could be connected to the > controller with two connections, one which adds a resistance and the > other > which is limited by a few large NTC inrush preventers. The current would > prefer the resistance path until the NTCs "close." This may provide > additional time to make the NTCs useful. > > One active method is to use the overcurrent protection mechanism in the > Open Revolt controller and prevent/take over the mosfet gate signal if a > hall sensor detects current that is too high: > > http://ecomodder.com/forum/showthread.php/paul-sabrinas-cheap-diy-144v-m > otor-controller-6404-161.html#post108442 > > While I would prefer to use a passive process, I am leaning toward the > active method. > > Thanks for all of the good information on this list, especially to Lee > Hart > for this issue in particular. > > Adam > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140811/b90c > 47b6/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) > _______________________________________________ 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)
