I was able to find a transformer in an old datacenter UPS which was very large. I also had some leftover 7 lamination flexible copper bus bar from the Chevy Volt battery teardown. I purchased some replacement shrinkwrap and wound it around 4.5 times. As the transformer I used had alternating E/I laminations, I separated each lamination and put it back together with all the Es on one side and Is on the other. I did not bother re-lacquer the laminations, so some laminations registered lower resistance, but most were isolated. I don't think this transformer had any shunts which Lee referred to, but I am not sure exactly what he is referring to. Pictures are available in the following links. Can someone confirm that this is the format people were expecting?
I hooked it up to test the other day and it did get warm (not that surprising), but the more surprising thing was the "click" when I put power through it. I don't have the I solidly against the E of the laminations, just a zip tie and some isolation paper which was in the transformer.. Peter mentioned a 1/8" air gap, would that refer to the distance between the I and the E laminations? Does this distance of this gap matter? What does this gap accomplish and what is the most effective way to achieve that? It is hard to believe that this will be enough to keep the controller from blowing up by running away with the current, but I guess it only needs a little inductance to prevent runaway. IMG_20141027_082635.jpg <https://docs.google.com/a/chasen.name/file/d/0ByKYdk2V0X2damJ3UU9BZG8xTzA/edit?usp=drive_web> IMG_20141027_082645.jpg <https://docs.google.com/a/chasen.name/file/d/0ByKYdk2V0X2dZmkxUGtnNDJsOHc/edit?usp=drive_web> Chris, You are correct! I was able to confirm just by setting the PWM low enough to see that the motor wouldn't continue to spin past a certain speed. Looks like I am still running the 100% original Presolite 4001 MTA. I do get it pretty hot on the highway though. What would the recommended max temperature be? Occasionally it is painful to touch. Thanks, Adam On Mon, Aug 11, 2014 at 8:37 PM, Chris Tromley <[email protected]> wrote: > On Mon, Aug 11, 2014 at 5:15 PM, Adam Chasen via EV <[email protected]> > wrote: > >> 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. > > > I can't help with the more electronical questions posed here, but a > minor point - the original Leopard motor is not series wound. It's a > compound wound. Not sure if that's pertinent to the discussion. Also, > I've never heard of anyone with an electric motor with a manual > transmission or direct drive that chooses to use the clutch. That's > generally considered an awkward work-around for a problem that should be > fixed. > > As for Cor's suggestion of using a microwave transformer core to make an > inductor, my township's municipal services yard has an area where residents > can drop off old appliances. There are almost always several discarded > microwaves there that haven't been hauled away yet. > > Chris > On Tue, Aug 12, 2014 at 12:13 PM, Peter Gabrielsson < [email protected]> wrote: > I used a laminated core about the size of of a 1-2 kVA isolation > transformer, added a 1/8" airgap and put about 3-4 turns on it. Can't > remember exactly since it was a while ago and it's burried under the > battery boxes now. > > A large microwave transformer core would be ideal. They're pretty cheap on > ebay if you don't want to go scrounging in the junk bins. > > > On Mon, Aug 11, 2014 at 2:15 PM, Adam Chasen via EV <[email protected]> > wrote: > >> 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-motor-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/b90c47b6/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) >> >> > > > -- > www.electric-lemon.com > -------------- next part -------------- An HTML attachment was scrubbed... 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