Steve, Either use two sets of matched MOSFETs and an opamp for each set to drive them to the desired channel resistance, controlled by the single input potbox, or find controllers that accept an input control *voltage* instead of resistance, so you can do the trick with just an opamp. BTW, for a SepEx motor controller setup it is always good safety to drop the contactor as soon as field current disappears.
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 Steve Powers Sent: Tuesday, January 28, 2014 6:14 PM To: [email protected] Subject: Re: [EVDL] ETV-1 Prototype up for sale on e-bay Looks like the ETV-1 got a lot of press this week and will sell. Several people have bid on it on e-bay. I hope the winner is a collector. In hindsight, I know know (10 years later) how I could have fixed the controller problem. The car would have been fine if I had been able to rig up a decent 108V SepEx controller. Today, it is irrelevant because the car has been fitted with a AC motor, probably higher voltage. For the benefit of others stuck with a >84V system and need a SepEx controller, there are options. Easiest is Kelly Controller. They will actually make one based on your supplied set of field parameters. But, you may not know what you need. In that case, you can use two controllers. For the Armature, use something like a Curtis 1231C. For the field, you don't need that big of a controller. But, get something rated for the voltage of your pack. Now, build a "black box" to go between your throttle and the inputs of those two controllers. Start the field at full (knowing full is not full battery voltage, it is probably 30% of full battery voltage) and probably keep it flat line at full until about 50% throttle. Then, at 50% throttle start ramping it down to maybe 1/2 or 1/3 full by the time you hit 100% throttle. At the same time, start the armature at 0% and gradually ramp it up to 100% at about 50% throttle. Then, hold it at 100% throttle as the field ramps down. That would actually work. I did something similar but I only used two discrete stages on the field so I didn't get the best speed control. Building that black box wouldn't be that difficult. You take in one variable resistor (0-5k) and you output two different 0-5k type resistance values. The trick is that they have to be continuous. You can't just use a series of contactors and flip through the field settings. The motor would attempt to spin out of control during the transitions of 0 field current (unless you also drop out the armature BEFORE you drop out the field). You would also have to reengage the field BEFORE reengaging the armature. This is no small task if you are trying to build a multistep contactor controller. Ten years later, I think the two controllers with black box between them is the best method. May prove to be some value to someone with a Soleq or TeVan in need of a controller. Just because it isn't on the market doesn't mean it can't be done with off the shelf parts. Steve -- View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/ETV-1-Proto type-up-for-sale-on-e-bay-tp4667626p4667693.html Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com. _______________________________________________ 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)
