# Initial regen experiments with a Soliton 1



## Qer (May 7, 2008)

We've been a bit busy lately with exploring the nature of series wound motors running in regeneration mode. Since we know that series wound motors are fairly instable when running as generators (1/(1-x) isn't a good formula in any physics...) we've taken baby steps but earlier today we did the first successful test with a rotating motor. It's a siamese setup where one motor is powered by one controller (a Junior to be precise) and a Soliton 1 (only Soliton 1 has the capability for regen, Junior hasn't) connected to the other and loaded with some modified software and after some happy cludge'R'us the experiment actually was successful.










As you can see the motor only delivered mere 25 Amps so it's not really useful yet, but the test setup couldn't handle much more so we didn't push it. It seems the Soliton might need a few external components to make regen handle (for series wound that is, PM-motors is a different story which we haven't tried) so there's some additional contraptions to be built before we can continue to pursue useful regen, not to mention that the software currently used is a horrible cludge that has to be rewritten and made a bit more proper... 

Anyway, regen is apparently possible with the Soliton. *This is not a guarantee that we will add the feature* (we still don't know if we'll run into unsolvable problems later on) but we're at least actually looking at it. Maximum current, pack voltage, motor types, extra equipment needed etc is still to be figured out so don't hold your breath quite yet...


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## Batterypoweredtoad (Feb 5, 2008)

Lol-that's awesome! If you pull off reliable regen with a series motor you will put another positive in the DC column in the ongoing AC/DC debate.


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## Inframan (Jan 30, 2011)

Very cool  can't wait to see more progress. Do you plan on making any videos like the arcing tests?


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## rwaudio (May 22, 2008)

I think Soliton1 regen would be awesome! More so for saving the brakes than capturing much useful energy, but great no matter what.


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## Tesseract (Sep 27, 2008)

Right now we're still just tinkering with regen because while we knew that it was technically possible, we had no idea how practical it would be, especially after hearing so many horror stories about the Zapi controllers with regen blowing up the first time it is enabled.

So at this point we're just trying to answer some basic questions about regen with the series motor (aka "series generator"). So some little tidbits of info we've learned so are:

1. You need to flip the polarity of the field winding to turn the series motor into a generator, but once you do that you need only place a load across the "generator" terminals to get it to actually start putting out power.

2. The polarity of the output voltage from the series generator depends on the orientation of the residual magnetism, and that depends on the direction the motor was traveling prior to flipping the field over to generating mode.

3. So far most of the testing has been done on a WarP-9 as our dyno has two which makes it really convenient to use one as a motor and the other as a generator. I have pulled as much as 150A through the generating motor and it seems okay. I'll have to actually remove the blower to see how bad the arcing on the brushes is, but in my experience brush arcing makes a very distinctive noise and I'm not hearing it, so why stop now?

4. The series generator *is* definitely unstable, but it doesn't seem to be insurmountably unstable. For the very first test I simply used a big resistor (350W and 0.15 ohms) as a load on the generator and observed that current did, indeed, increase until the braking torque from the generator was sufficient to slow down the motor - something that might not occur until it's too late if the motor/generator is being turned by a car descending a long, steep grade! My next test - which revealed even more instability - was to load the generator with a constant current, rather than a constant resistance. I used my trusty MOSFET-based 400A/200V CC load to do this, conservatively set - or so I thought - to 100A. Unfortunately, to make a MOSFET pass a constant current you need a feedback loop (one for each MOSFET, actually) and that feedback loop then interacted with the unstable series generator to create huge oscillations that eventually *blew up* the CC load. A CC load made with bipolar transistors would be much more stable, but that leads us to our next issue...

5. The series generator doesn't put out more than a fraction of a volt until sufficiently loaded (how much is sufficient isn't yet known) but the voltage drop across an IGBT (or a bipolar transistor) is at least 0.6V so even when it is turned on the generator can't tell it is being loaded as its voltage isn't high enough to overcome the "on" voltage of the IGBT. This means there needs to be another load placed across the generator to ensure the terminal voltage exceeds 0.6V at all times.

More will follow, but for now it appears that regen with a series motor is certainly possible, but maybe not too practical given the need to flip the field polarity and ensure there is always some minimum load present to insure generation always occurs.

Oh, and most importantly, we've managed to push a peak charging current of 2A back into the 159V (actual) battery pack 

Oh, and yeah, I'll try to remember to video some of the testing next time, inframan 

So take that, AC....


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## Batterypoweredtoad (Feb 5, 2008)

Tesseract said:


> .
> 
> Oh, and most importantly, we've managed to push a peak charging current of 2A back into the 159V (actual) battery pack
> 
> ...



First 2A, then 200A, then 2!

I just find it amusing that you don't want to build an AC controller, but you do seem interested in pushing them down and taking their toys away.


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## Qer (May 7, 2008)

Batterypoweredtoad said:


> First 2A, then 200A, then 2!


We only managed to trickle a few Amps back into the pack but Tesseract managed to dump some serious current into a dummy load and generate quite some Watts pure heat from it, which I guess is perfect in Florida to counter that cold, almost Siberia-like climate they have to suffer over there...



Batterypoweredtoad said:


> I just find it amusing that you don't want to build an AC controller, but you do seem interested in pushing them down and taking their toys away.


Just because we decided we wanted to do a picnic on Mount Wycheproof doesn't mean that we're prepared to take on Mount Everest. And well, Soliton 1 was regen ready from the beginning, can as well try to see if it can be used for something too, eh? Especially since there's now quite a selection of natural timed high voltage motors on the market.

EDIT: T pointed out that my engrish probably played tricks on me again, both in interpreting a mood that didn't exist in Batterypoweredtoads post and making my reply more harsh than what it really needed to be. Apologizes for that.


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## Batterypoweredtoad (Feb 5, 2008)

Nah, no ill will on my part towards you or Tess, just a little good natured ribbing. I like the stuff you guys do and think this board and the community in general benefit from your presence. Please keep pushing and keep talking about, I like the posts. Group hug!


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## Tesseract (Sep 27, 2008)

Batterypoweredtoad said:


> First 2A, then 200A, then 2!
> 
> I just find it amusing that you don't want to build an AC controller, but you do seem interested in pushing them down and taking their toys away.


One of the biggest obstacles to actually implementing regen in the Soliton1 was how to deal with advanced timing motors. The conventional wisdom is that you can't do regen with an advanced timing motor like the ever popular WarP-9 because it'll immediately blow up in a fiery ball of plasma. Recently, though, I came up with the half-baked* justification that because regen is just like reverse, whatever current/voltage limit a WarP-9 can tolerate in reverse should be fine for regen, too. So far that does appear to be the case, so I'll keep increasing the RPM and regen current until the brushes start arcing and then we'll hard code limits into the Soliton1 well inside those parameters so regen is safe regardless of the type of motor used. 

Oh, and our reluctance to develop an AC motor controller is strictly the result of economics - even if every one of our past and future DC controller customers switched over to our hypothetical inverter it would still take several years of sales to pay back the development cost, and that's just too much risk for a small business like Evnetics. We'd be much better served developing complementary products like chargers, dc/dc converters, etc..., rather than another motor controller (it's a similar argument for why we haven't bothered to pursue a higher power DC controller, too).


* - unlike FX's late night programming (e.g. - "Archer") which is "fully baked".


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## Yabert (Feb 7, 2010)

Tesseract said:


> One of the biggest obstacles to actually implementing regen in the Soliton1 was how to deal with advanced timing motors.


+2 for the interpoles!! (+1 being the capacity to run at high voltage).


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## Tesseract (Sep 27, 2008)

Yabert said:


> +2 for the interpoles!! (+1 being the capacity to run at high voltage).


No argument from me on that, but there are overwhelmingly more advanced timing motors in use in EVs and as a "responsible controller manufacturer" I have to account for human nature, which says that people will resoundingly ignore all warnings concerning the danger of high regen currents with such motors.

Hence, should we officially implement regen in the Soliton1 code we will have to limit the maximum regen current to something that can't hurt a WarP-9, even though a WarP-11HV or a Kostov-11 could take a whole lot more.


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## FarFromStock (Mar 16, 2009)

Subscribing! 

Keep up the great work guys! These potential future enhancements just solidify my confidence that I made the right decision in chosing the Soliton and Rebirth for my conversion.

I really appreciate that you guys just won't leave well enough alone.


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## DawidvC (Feb 14, 2010)

FarFromStock said:


> I really appreciate that you guys just won't leave well enough alone.


Ditto! Keep it up!

Dawid


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## ECCM (Apr 13, 2010)

So a neutral timed Kostov 11 HV will be able to regen with Soliton 1?

I think that's a smart business decision. Offer a very important feature that's been elusive in the DC world. First, offer a true continuous 1000 A controller, a simple to use controller without having to add a bunch of components, and now regen.

I am sold. When can I purchase a Soliton 1 with regen?

Put me on a waiting list.


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## Dennis (Feb 25, 2008)

A DC motor is actually easier to get enough voltage boost to charge batteries than from the AC motor. What matters is the type of DC motor we are talking about here. A sep-ex motor can easily do regen by over exciting the field such that it causes the volts/rpm constant to go up and therefore produce a voltage output higher than what ran the motor at that speed. 

All DC motors can also by dynamically braked by placing a load resistor on the output when the controller disengages, but getting a voltage boost out of a series wound motor is not an easy task unless you load it down with a very low resistance, but you guys can figure it out at EVnetics. Don't give up on us. Competition breeds innovation. Without you we would be stuck with the Zilla that seems to be hard to get a hold of.




Yabert said:


> +2 for the interpoles!! (+1 being the capacity to run at high voltage).



Now we need either Netgain or Kostov to add compensating windings to a 13" with interpoles and the motor will be golden! The ultimate DC mean machine with a much higher voltage rating.


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## Jozzer (Mar 29, 2009)

Tesseract said:


> One of the biggest obstacles to actually implementing regen in the Soliton1 was how to deal with advanced timing motors. The conventional wisdom is that you can't do regen with an advanced timing motor like the ever popular WarP-9 because it'll immediately blow up in a fiery ball of plasma. Recently, though, I came up with the half-baked* justification that because regen is just like reverse, whatever current/voltage limit a WarP-9 can tolerate in reverse should be fine for regen, too. So far that does appear to be the case, so I'll keep increasing the RPM and regen current until the brushes start arcing and then we'll hard code limits into the Soliton1 well inside those parameters so regen is safe regardless of the type of motor used.


 That's certainly the way it works with PM motors and regen, and due to the reletivly short and low loads gained by REGEN this works out quite well even on aggressivly timed motors. We do however have problems on the track, where the brushes are already running at peak. A little REGEN soon throws the balance when your near the edge already..
Steve


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## Yabert (Feb 7, 2010)

Dennis said:


> Now we need either Netgain or Kostov to add compensating windings to a 13" with interpoles and the motor will be golden! The ultimate DC mean machine with a much higher voltage rating.


Take one: http://kostov-motors.com/tractionmo...esdcmotorsforelectricvehicles/k13directdrive/


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## Salty9 (Jul 13, 2009)

Googling for DC motor regen I found this article by Otmar: http://www.cafeelectric.com/curtis/regen/index.html


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## Tesseract (Sep 27, 2008)

ECCM said:


> So a neutral timed Kostov 11 HV will be able to regen with Soliton 1?


The whole idea behind our tinkering is to see if we can *safely* do regen with *advanced timing* motors, and not just neutral timed ones like the Kostov's. I outlined the reasons why I feel this is important in a previous post.



ECCM said:


> I think that's a smart business decision. Offer a very important feature that's been elusive in the DC world. First, offer a true continuous 1000 A controller, a simple to use controller without having to add a bunch of components, and now regen.


Right now we are just tinkering with regen and sharing our results, not really declaring it to be an upcoming feature. I mean, we have a long way to go (and a lot of IGBTs to blow!) before we can feel safe adding regen to the code.

Also, regen with the series motor is kind of kludgy because it needs a reversing contactor which might get actuated hundreds of time on every drive if used for regen, rather than just a couple of times if used strictly for reverse.

Anyway, the upshot of all this is that we are mainly just having some fun, not unlike Otmar did many years ago when he kludged a Curtis into doing regen; you may notice that Otmar never did include regen braking into the Zilla controllers... (and I can kind of see why he made that decision  )

(yes, Salty9, Otmar's work is well known to those of us "in the biz")


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## Tesseract (Sep 27, 2008)

Dennis said:


> ...but getting a voltage boost out of a series wound motor is not an easy task unless you load it down with a very low resistance, but you guys can figure it out at EVnetics. Don't give up on us. Competition breeds innovation. Without you we would be stuck with the Zilla that seems to be hard to get a hold of....


Heh... well, I'd say our tinkering is more the result of me and Qer being incorrigible tinkerers rather from us feeling pressured by competition.

That said, you are correct that it takes an awfully low load resistance to get the series motor to regenerate (and, apparently, to keep it regenerating). I'm going to see if a constant current sink made with bipolar transistors can act as that load (something that can take up to 200V of Vce while passing a constant 1A - so 200W of dissipation) first, then I'm going to try tickling the field with constant current power supply to see if that works reliably. 

Anyway, now that I know we can do regen with the Soliton1, I'll do a less cobbled-together setup next time I get a chance to monopolize the dyno and video some of the testing.

(and keep those technical comments coming - we're more or less swinging at the pinata with blindfolds on right now).


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## Qer (May 7, 2008)

ECCM said:


> When can I purchase a Soliton 1 with regen?


That I wonder too...


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> (and keep those technical comments coming - we're more or less swinging at the pinata with blindfolds on right now).


I've been thinking about this problem too, and have a possible scheme to make regen stable, but on a compound wound motor rather than straight series. Maybe I would call it semi-SepEx because the second set of coils would either strapped directly to the battery or run through a low power controller. Now you have a stable generating voltage that actually decreases when you draw more current. The series coils give you plenty of inductance to keep the Soliton happy.
You could probably include software traps to keep regen from being enabled on a straight series motor. 
Gerhard
PS I will start a thread soon to show some interesting characteristics of such a motor, including a flattened power curve. G.


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## Tesseract (Sep 27, 2008)

GerhardRP said:


> I've been thinking about this problem too, and have a possible scheme to make regen stable...


We seem to have a good handle on the stability problem caused by the dual right-half-plane zeros (one for the boost converter, one for the series generator) but the real issue is that the motor won't regenerate with just the controller connected - there needs to be an additional load across the motor at all times. I thought that the saturation voltage of the IGBTs might be the problem, but that wouldn't explain why regeneration stops when I take away the 0.15 ohm load despite the terminal voltage being well above Vce[sat] (ie - even as high as 12V, so ~80A was flowing through the resistor!)

Today or tomorrow I'm going to see if a bipolar current sink pulling a mere 1A through the motor whenever it is in regen mode - regardless of terminal voltage - will solve the problem as that would be a much more elegant solution than using a huge resistor as the load. I will also try feeding just the field windings with an isolated CC power supply to see if that works. Whichever one is less expensive/more reliable to implement wins.



GerhardRP said:


> but on a compound wound motor rather than straight series. Maybe I would call it semi-SepEx because the second set of coils would either strapped directly to the battery or run through a low power controller.


Adding another winding takes all the challenge out of it, Gerhard... It also doesn't help the motors already in existence. 



GerhardRP said:


> You could probably include software traps to keep regen from being enabled on a straight series motor.


But that's the whole point of this thread...  - getting regen to work with a "straight" series motor (advanced or neutral timed, interpoled or not, etc.).


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## jackbauer (Jan 12, 2008)

Tesseract , I'm guessing your familliar with this article and associated videos?

http://electricmobile.ru/regenarative-braking-on-series-dc-motor/

.......the motor is question is neutrally timed.


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## Tesseract (Sep 27, 2008)

jackbauer said:


> Tesseract , I'm guessing your familliar with this article and associated videos?
> 
> http://electricmobile.ru/regenarative-braking-on-series-dc-motor/
> 
> .......the motor is question is neutrally timed.


Yep, I remember that thread. His approach is to basically turn a series motor into a sepex. The big problem here is that field excitation is fixed and there is no means of limiting armature current, once (if?) armature voltage exceeds pack voltage.

If I use external excitation of the field instead of a resistive or CC load to maintain regeneration it will only be a few amps at most, so field current will be, at most, just a few more amps than armature current, so commutation will occur more or less the same as usual.


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## coryrc (Aug 5, 2008)

Tesseract said:


> Also, regen with the series motor is kind of kludgy because it needs a reversing contactor which might get actuated hundreds of time on every drive if used for regen, rather than just a couple of times if used strictly for reverse.


Only if you don't have synchronous rectification


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## Tesseract (Sep 27, 2008)

coryrc said:


> Only if you don't have synchronous rectification


Not sure what you mean by this... you must reverse the polarity of the field relative to the armature to make the series motor regenerate and synchronous rectification doesn't factor into this at all.


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## Dennis (Feb 25, 2008)

Yabert said:


> Take one: http://kostov-motors.com/tractionmotors/kostovevmotors(ac-dc)/seriesdcmotorsforelectricvehicles/k13directdrive/



I am sure the motor has interpoles, but I do not think it has compensating windings as well. Compensating windings would be embedded into the faces of the stator poles like this:










Notice the copper buss bars running through the stator parallel to each other. That is the compensating windings and to the right of the stator pole you see the interpole.


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## coryrc (Aug 5, 2008)

Tesseract said:


> Not sure what you mean by this... you must reverse the polarity of the field relative to the armature to make the series motor regenerate and synchronous rectification doesn't factor into this at all.


Oops, I remembered that wrong and tried to make a joke... oh well.


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## Tesseract (Sep 27, 2008)

coryrc said:


> Oops, I remembered that wrong and tried to make a joke... oh well.


Ah, I think I can just about get it now... *rimshot*


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## Agust Sigurdsson (Oct 25, 2009)

jackbauer said:


> Tesseract , I'm guessing your familliar with this article and associated videos?
> 
> http://electricmobile.ru/regenarative-braking-on-series-dc-motor/
> 
> .......the motor is question is neutrally timed.


Hi.
What this russian guy does to obtain regen is to feed excitation current from the 12V battery in some controlled manner to the stator windings and separate the armature current from the stator current. As far as I can evaluate this concept I find it nothing short of brilliant. In effect he turns a series motor into sepex when he wants to regen. 
If we replace the battery with a controllable isolated DC/DC converter running off the main battery pack I believe that we have a good concept to start with. The DC/DC converter should be designed to deliver quite a lot of amperes but at a low voltage so the total wattage used would be low.
I do not have the facilities to test this concept out but for those who have it all it would not take more than hooking together some high current diodes and a bench power supply (or a 12V battery plus some suitable resistors) to get a proof of concept. Designing the DC/DC converter should be trivial as soon as we know how much current and voltage it should deliver.

Any comments ?


Agust


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## Tesseract (Sep 27, 2008)

Agust Sigurdsson said:


> Hi.
> What this russian guy does to obtain regen is to feed excitation current from the 12V battery in some controlled manner to the stator windings and separate the armature current from the stator current. As far as I can evaluate this concept I find it nothing short of brilliant. In effect he turns a series motor into sepex when he wants to regen.


Actually, the field (stator) current is *not* controlled - it depends only on the total circuit resistance and battery voltage. Worse to me is that the armature (rotor) current is not controlled, so regen current will be unpredictable once armature voltage exceeds battery pack voltage.

Not trying to diminish the guy's efforts, mind you, just pointing out some of the problems I see with that particular approach.



Agust Sigurdsson said:


> If we replace the battery with a controllable isolated DC/DC converter running off the main battery pack I believe that we have a good concept to start with.


Yeah - I sort of already mentioned this as an alternative approach... It may well prove to be the most practical, if not the least expensive, way to enable regen with a series motor, but I'd like to test the simpler methods more thoroughly, first.


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## jackbauer (Jan 12, 2008)

If you look on some of his videos , he has a pot on the gearstick which he uses to adjust regen current. On his website he is selling a box for i think $100 that has a heatsink by the look of it. I'd guess its some sort of dc dc as August suggested?


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## Russco (Dec 23, 2008)

jackbauer said:


> If you look on some of his videos , he has a pot on the gearstick which he uses to adjust regen current. On his website he is selling a box for i think $100 that has a heatsink by the look of it. I'd guess its some sort of dc dc as August suggested?


So what's the B*D with series motor regen? 

I was doing regen. with the series Prestolite motor in 1982.

Easy as pie...I purchased a Trojan 200 AH LA cell for $25. Connected this 2 volt volt cell thru a Ford type solenoid to the motor field in the same polarity as motoring.

For regen, just close the Ford solenoid thru a switch on the gearshift, which will provide 2 volts across the 0.01 ohm series field = 200 amps. When the armature voltage = greater than the battery voltage, the armature current reverses, passing thru the controller C-E diode and charges the batteries, slowing the car = real regenerative braking with a series motor.

So simple...best done by splitting the pack in two halves and paralleling the halves for regen.

I also had a dynamic braking system which used 30 feet of 0.125" stainless steel wire as a resistor connected across the armature via a contactor. Place the 2 volts across the field and the armature voltage across the resistor = lotsa current = slows down vehicle.

The regenerative or dynamic braking could lock the rear wheels if I was stupid enough to place the car in first gear with the clutch in, coast downhill to 35 MPH, then release the clutch = instant stop!

Ah, the things I did in my youth.

So, nothing new re: regenerative braking. Been there, done that. 

Russ Kaufmann

RUSSCO Engineering


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## Tesseract (Sep 27, 2008)

Russco said:


> So what's the B*D with series motor regen?
> 
> I was doing regen. with the series Prestolite motor in 1982.
> 
> ...


This results in an unpredictable and unregulated amount of braking torque proportional to the difference in armature voltage vs. battery pack voltage. In other words, braking is strongest at high RPMs, tapering off to nothing as the vehicle slows down. If the difference in Varm and Vbatt is high enough then you might lock up drive wheels or destroy the "freewheeling" diode from excess current, etc.

I'm trying to maintain a constant current from the motor during regeneration by using a boost converter to step up Varm to just barely overcome that of Vbatt. Charging current will always be equal to or less than regen current, there should be no arcing from the brushes even if they are advanced and you don't have to worry about the wheels locking up violently just because you happen to be engaging regen at a really high motor RPM. It won't be nearly as versatile as regen with an AC system, but it will be a whole lot better than energizing the field and praying all of the salient parameters are within certain limits


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> This results in an unpredictable and unregulated amount of braking torque proportional to the difference in armature voltage vs. battery pack voltage. In other words, braking is strongest at high RPMs, tapering off to nothing as the vehicle slows down. If the difference in Varm and Vbatt is high enough then you might lock up drive wheels or destroy the "freewheeling" diode from excess current, etc.
> 
> I'm trying to maintain a constant current from the motor during regeneration by using a boost converter to step up Varm to just barely overcome that of Vbatt. Charging current will always be equal to or less than regen current, there should be no arcing from the brushes even if they are advanced and you don't have to worry about the wheels locking up violently just because you happen to be engaging regen at a really high motor RPM. It won't be nearly as versatile as regen with an AC system, but it will be a whole lot better than energizing the field and praying all of the salient parameters are within certain limits


Perhaps try Rusco's approach, but put the external current through only one pair of field coils, with the other pair still in series with the armature. This would reduce the generated voltage as the current increases. You can still use the boost converter.
Gerhard


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## Tesseract (Sep 27, 2008)

GerhardRP said:


> Perhaps try Rusco's approach, but put the external current through only one pair of field coils, with the other pair still in series with the armature. This would reduce the generated voltage as the current increases. You can still use the boost converter.
> Gerhard


Good idea except that the Warp-9 and Kostov-9 both have a single set of field terminals.... At this point what I really need to determine is how much of a load - or excitation - I need to supply to the motor to allow the boost converter to work. Right now the controller simply refuses to regenerate without the load (haven't tried external excitation of the field yet) and even stops regenerating if the load is taken away, despite the terminal voltage exceeding the IGBT Vce[sat].


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## Russco (Dec 23, 2008)

Tesseract said:


> This results in an unpredictable and unregulated amount of braking torque proportional to the difference in armature voltage vs. battery pack voltage. In other words, braking is strongest at high RPMs, tapering off to nothing as the vehicle slows down. If the difference in Varm and Vbatt is high enough then you might lock up drive wheels or destroy the "freewheeling" diode from excess current, etc.
> 
> Certainly, the driver, through poor driving judgment, can over-regen, leading to unsafe braking or broken components.
> 
> ...


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## GerhardRP (Nov 17, 2009)

Russco said:


> For regen, just close the Ford solenoid thru a switch on the gearshift, which will provide 2 volts across the 0.01 ohm series field = 200 amps. When the armature voltage = greater than the battery voltage, the armature current reverses, passing thru the controller C-E diode and charges the batteries, slowing the car = real regenerative braking with a series motor.
> 
> Russ Kaufmann
> 
> RUSSCO Engineering


Am I right that you left the armature and field coils still in series? If so, this configuration is stable. When the generated current increases, the field current drops. If the generated current reaches 200 Amps, the field current would be zero, so zero volts.
EDIT:There will need to be a resistor in the battery circuit to allow the field voltage to fall without shorting the battery.
Gerhard


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## Plamenator (Mar 6, 2009)

Tesseract said:


> Good idea except that the Warp-9 and Kostov-9 both have a single set of field terminals.... ].


Not quite true - both K9" 220V and K11" 250V have field switching which seems to be what you are after.
http://kostov-motors.com/tractionmo...dc)/seriesdcmotorsforelectricvehicles/k9220v/

The 4 series coils are separated 2x2 and each pair has 2 terminals.

You can go even further - a compound motor where 2 of the coils are sepex style (many turns of fine round wire) and 2 are series (few turns of big rectangular wire). Both pairs can have separate terminals. Then maybe you can use the sepex style coils for regen.


Unfortunately this deviates from Tesseract's desire to use a standard motor.


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## Plamenator (Mar 6, 2009)

Actually the motor in the above picture has 8 terminals in total (was a very custom motor ).
The last 2 are for the interpole windings.
Not very familiar with regen, but can the interpoles be used in some way during regen? If regen happens at lower voltages, they may not be needed during regen?


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## Tesseract (Sep 27, 2008)

GerhardRP said:


> Am I right that you left the armature and field coils still in series? If so, this configuration is stable. When the generated current increases, the field current drops. If the generated current reaches 200 Amps, the field current would be zero, so zero volts.
> EDIT:There will need to be a resistor in the battery circuit to allow the field voltage to fall without shorting the battery.
> Gerhard


Yep - this is stable and I can confirm that it works, but even with 50A of field excitation the open circuit voltage of a WarP-9 was only 17V at 3000 rpm. And you can't use a boost converter to step that voltage up because, as you also correctly note, the generated current opposes the field current. This just doesn't seem remotely practical, but it is quite stable.




Plamenator said:


> Not quite true - both K9" 220V and K11" 250V have field switching which seems to be what you are after...


The pair of 144V K9's that are sitting in front of me right now only have 4 terminals, so any scheme that relied on separating the paired fields and exciting just one of them wouldn't work with these motors (nor the WarP-9, Advanced DC FB series, D&D, etc...).


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> Yep - this is stable and I can confirm that it works, but even with 50A of field excitation the open circuit voltage of a WarP-9 was only 17V at 3000 rpm. And you can't use a boost converter to step that voltage up because, as you also correctly note, the generated current opposes the field current. This just doesn't seem remotely practical, but it is quite stable.


 So feed it with 500 Amps from a Soliton Jr.


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## Agust Sigurdsson (Oct 25, 2009)

Tesseract said:


> Yep - this is stable and I can confirm that it works, but even with 50A of field excitation the open circuit voltage of a WarP-9 was only 17V at 3000 rpm. And you can't use a boost converter to step that voltage up because, as you also correctly note, the generated current opposes the field current. This just doesn't seem remotely practical, but it is quite stable.




This implies that we would require over 400 Amps of excitation current if we want to generate 144 Volts (assuming that is the battery voltage). If we want regen below 3000 RPM we would have to increase the excitation current proportionally.
Designing the DC/DC converter or whatever it takes to generate the excitation current is obviously becoming an engineering challenge. 

B.t.w. does someone on this forum know the typical values of the electrical resistance and inductance of the stator alone in large series motors such as Warp-7 thru -9 ?

Agust


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## Tesseract (Sep 27, 2008)

GerhardRP said:


> So feed it with 500 Amps from a Soliton Jr.


No-can-do: the source of field excitation needs to be isolated from the traction battery.



Agust Sigurdsson said:


> This implies that we would require over 400 Amps of excitation current if we want to generate 144 Volts (assuming that is the battery voltage).


It would appear that is the case. I'd hardly call my testing exhaustive, but given that I blew up my 400A constant current load in previous tests 50A was all I could manage with the junk on hand at the shop.



Agust Sigurdsson said:


> B.t.w. does someone on this forum know the typical values of the electrical resistance and inductance of the stator alone in large series motors such as Warp-7 thru -9 ?


I just have data on the WarP-9 and only for the whole motor, not just the stator. I can make the stator-only measurements this weekend. Note that the inductance is somewhat inversely proportional to current because of saturation.

EDIT: resistance of the field (stator) is 4 milliohms (0.200V drop at 50.0A); I had previously measured 7 milliohms total for the motor and 100uH (based on ripple current fraction at 400A). Once I get a measurement on the field ripple fraction I'll edit this again with the inductance.


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> No-can-do: the source of field excitation needs to be isolated from the traction battery.


I'm not sure of that. If the wireing is Soliton1 positive to armature, then field then to Controller minus. The junior shares the minus connection and the plus goes to the top of the field.
Gerhard


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## Tesseract (Sep 27, 2008)

GerhardRP said:


> I'm not sure of that. If the wireing is Soliton1 positive to armature, then field then to Controller minus. The junior shares the minus connection and the plus goes to the top of the field.
> Gerhard


Yes, that is how it must be wired to even work, but my main concern is that the anti-parallel and freewheeling diodes in Junior provide additional, and undesirable, pathways for current during _motoring_ operation. I quickly sketched your proposed scheme in TINA (a halfway decent SPICE program from TI which is a little easier to use than Linear Tech's LTSpice) to make it easier to visualize the potential gotchas.

It looks like it would only take inserting a contactor in between the field (+) and Jr to solve this problem, but you still must contend with regen only being available at relatively high RPMs, particularly if the pack voltage is high, and braking torque from regen being somewhat unpredictable (though with a known limit due to a known maximum amount of excitation current).


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## bruceme (Dec 10, 2008)

Tesseract said:


> Also, regen with the series motor is kind of kludgy because it needs a reversing contactor which might get actuated hundreds of time on every drive if used for regen, rather than just a couple of times if used strictly for reverse.


Since amps are limited by the advance, what about permanently mounting a small 30A controller in reverse, or setting up a second smaller (MOSFET?) reversed gate set (asymmetric h-bridge)? I don't really "need" regen, but I sure would like "engine breaking".

Oh, I'm curious... what's the status? Is this going to release?

-Bruce


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## Tesseract (Sep 27, 2008)

bruceme said:


> Since amps are limited by the advance, what about permanently mounting a small 30A controller in reverse


30A through the field won't get you much in the way of regeneration; you need to put at least 200A through it for this scheme to worth the added complexity



bruceme said:


> ...or setting up a second smaller (MOSFET?) reversed gate set (asymmetric h-bridge)?


You can't just reverse the polarity of current through the entire motor, you have to reverse polarity through the field while the armature is spinning in the "forward" direction for regeneration to occur; an H-bridge ain't gonna cut it. 

Unless you mean turning the series motor into a hammy-jammy SepEx motor, with a field controller that has beefy IGBTs for the forward direction and wimpy ones for the regen/reverse direction. Sure, that would work, but it would require an entirely new controller.



bruceme said:


> Oh, I'm curious... what's the status? Is this going to release?


Depends on how much more for a Soliton1 people like you would be willing to pay for it to have this feature... In the range of $0-$50 per controller I am completely disinterested; at somewhere around $100 it doesn't seem so much like a doomed folly and at $500 per I will re-prioritize what I am doing and put this first.


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## ElectriCar (Jun 15, 2008)

I'm game. It would be worth something for sure to have it for braking and range extension. I wouldn't be interested in using contactors however for switching preferring power electronics instead, no arcing, no clunking, no wear and very fast.


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## bruceme (Dec 10, 2008)

Tesseract said:


> 30A through the field won't get you much in the way of regeneration; you need to put at least 200A through it for this scheme to worth the added complexity


I think you're missing the point of it... I don't really want 100% maximum regen... I really just want something that makes it feel more like a real car. 30/50/80A; somewhere in that range is an amount that makes my car feel like when I pull off the "gas" pedal, it slows down.

I honestly don't understand all the complex field compensations, but if it's something that can be done... why not? I'm a daily commuter, for a good quality $2500 controller, it would be worth an additional $200 to me. 

Here's my math: If it can prevents 30% of my brake wear, they cost $150/set. I replace them every year (20,000 miles). That's a "brake"-even  in 4.4 years. I would spend that.

Given it doesn't blow up in any real world scenario (high/low RPM, wet snow hot or cold) or significantly ware my brushes.

Market point of 1... Do with it what you can.

-Bruce


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## bruceme (Dec 10, 2008)

Here's a dirt simple idea... Let's take a lesson from Diesel-Electric Trains; dynamic breaking. Setup a totally separate circuit that dumps all the current into a cheap ceramic heater core? There's not much field math there is there? The controller should manage it to keep it from getting turned on accidentally.

Just a thought... thanks


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## piotrsko (Dec 9, 2007)

Tesseract said:


> Depends on how much more for a Soliton1 people like you would be willing to pay for it to have this feature... In the range of $0-$50 per controller I am completely disinterested; at somewhere around $100 it doesn't seem so much like a doomed folly and at $500 per I will re-prioritize what I am doing and put this first.


Does this mean for $500 you'd send me Sol1.X OS with regen?


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## Tesseract (Sep 27, 2008)

ElectriCar said:


> I'm game. It would be worth something for sure to have it for braking and range extension. I wouldn't be interested in using contactors however for switching preferring power electronics instead, no arcing, no clunking, no wear and very fast.


 In other words, you'd prefer to use a separate floating power supply to energize the field for regen braking? That requires the most expensive hardware, but less modification to the controller software.



bruceme said:


> I think you're missing the point of it... I don't really want 100% maximum regen... I really just want something that makes it feel more like a real car. 30/50/80A; somewhere in that range is an amount that makes my car feel like when I pull off the "gas" pedal, it slows down.


No, I didn't miss your point; 30A of braking current is completely unnoticeable. It certainly won't make your EV behave more like an ICE nor will it save wear on pads, rotors, etc. I feel you would need at least 100A of motor current during regen for it to be worthwhile, with 200-300A being much preferred. Anything more is too risky with an advanced motor, especially at high boost conversion ratios (ie - as RPM declines).




piotrsko said:


> Does this mean for $500 you'd send me Sol1.X OS with regen?


Maybe; depends on how we implement regen. The way ElectriCar wants to do it would require me designing some expensive hardware, but it wouldn't require as much work on the software as using contactors to flip the field polarity. The latter option requires no special hardware aside from the reversing contactors, but a whole bunch of changes to the software, and a very tedious vetting process to ensure everything works safely and reliably.


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## bruceme (Dec 10, 2008)

Hey thanks! That's good info. I hope it the capability makes it into some version some day.


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## valerun (Nov 12, 2010)

ElectriCar said:


> I'm game. It would be worth something for sure to have it for braking and range extension. I wouldn't be interested in using contactors however for switching preferring power electronics instead, no arcing, no clunking, no wear and very fast.


+1. We would pay $500 for a capability from EVnetics. Hell, even that russian guy is trying to sell his unit for $300 and I am sure you guys would make something at an entirely different quality/performance level.

V


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## piotrsko (Dec 9, 2007)

Tesseract said:


> Maybe; depends on how we implement regen. The way ElectriCar wants to do it would require me designing some expensive hardware, but it wouldn't require as much work on the software as using contactors to flip the field polarity. The latter option requires no special hardware aside from the reversing contactors, but a whole bunch of changes to the software, and a very tedious vetting process to ensure everything works safely and reliably.



OK just like when you were building the SOL1, Just let me know when and where to send the check. I can wait, especially for your stuff. If I'm early, do I get a firm price?

Which Russian guy? There are a bunch out there.


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## ElectriCar (Jun 15, 2008)

Savin' up, since a comparably priced AC option hasn't materialized in the four years I've been EV'in and isn't in the works anywhere it appears.


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## Tesseract (Sep 27, 2008)

piotrsko said:


> OK just like when you were building the SOL1, Just let me know when and where to send the check. I can wait, especially for your stuff. If I'm early, do I get a firm price?
> 
> Which Russian guy? There are a bunch out there.


Aw, thanks. I can't promise I will ever build a field controller for a series motor, but I have to admit the technical challenge of desiging a ~2-4V at 200A output power supply for it is intriguing. In contrast, doing regen with reversing contactors is kind of dull and uninspiring to me since it would be done almost entirely in software. I get to spend lots of tedious hours testing stuff, but not much actually designing stuff....

And the Russian guy is probably this dude who uses an external steering diode and a 12V battery to energize the field. Because the controller is not run in boost mode he needs to supply a huge current to the field (via the 12V battery) and the motor has to be spinning at a fairly high RPM before current will flow back to the battery pack through the switch's otherwise unused anti-parallel diode. It's probably a bit crude from a drivability standpoint - braking effect depend on RPM - but it's still a fiendishly clever bit of lateral thinking.


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## piotrsko (Dec 9, 2007)

FWIW, with the just alternator and power steering pump, I am sucking 100 amps at idle (about 16 hp), and on a 3% grade that will keep the Ranger from not increasing speed. 200 amps would be ideal.

So no regen then in the near foreseeable?


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