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Discussion Starter #1
Hello all! I've been lurking here a year or so absorbing all I can from the vast store of information here. Thank you, what a great forum. I'm ready to do some serious thinking about a conversion project. The vehicle is a 1987 Plymouth Sundance, which has the overriding attraction that I own it, know its foibles, and like it.

I keep veering toward the DC sepex motor. I like engine braking, so regen is attractive to me, because of the familiar feel. So I'm looking hard at the Kostov 11" sepex, good for 168 volts, equipped with interpoles, and probably too darn big to go in the Sundance, but that's just a detail...

I have concluded there are no sepex controllers out there that can realize the potential of this motor. I'm thinking of dual controllers. A big one for the armature, like a brushed PM with regen, and a baby one for the field. Then build a microcontroller interface to accept input from the pilot's foot and coordinate the controllers. Dumb? Let me have it, please.
 

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Are you looking at purchasing an 11" Kostov SepEx or do you have an 11" Kostov and you think its SepEx? I have two 11" Kostov Series Motors with interpoles and neither are SepEx. They could be used for Regen if a controller was available without having to deal with over seas and very slow companies. Your actually better off without the regen as you really don't need it. It would be good for helping stop the vehicle but with good disk brakes you'd be better off. The cost and complexity of doing regen on a series motor along with the fact that only one company really builds a controller that will allow regen with a series motor with interpoles. Not the best in terms of needing good close at hand customer support and availability of reasonable priced parts. A 9" would more than likely suit your needs just fine with a good series motor controller. Don't mess with dual controllers to try to make a SepEx run. If you must go sepex you can use the Kelly Controller but the controller is not a super high end one and will give marginal performance. Yes it will do regen but your better off with a good controller and a good series motor instead. I have been on the same page as you with regen with DC but after driving my 9" motor in my Ghia you really do not need regen. Really.

Pete :)
 

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Discussion Starter #3
Pete, thanks for your response. No, I don't have a motor, I'm looking at the Kostov-motors.com website, from which I posted the performance chart and drawing.

The price listed is $2,000 USD, which seems fair considering the motor specs. What have you concluded about the quality of Kostov?

Dan
 
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I like the Kostov but the new Kostov HV motors would be better. The Warp 11 would be better but the price is through the roof. My two Kostov motors are fine but the rpm range is not so high but then it's a large motor. My motor is good for 4500 rpm or so. I'd keep it a bit less. High torque so no need for real high rpm's. The new HV motors are better in the RPM range too and can handle higher voltages and you can advance the brushes. I am not sure if the Kostov SepEx motors are higher rpm or HV. I'd stick with a decent 9" or 11". 9" motors are far more common. I have a GE 9" and it runs real nice. My GE was purchased used and is still in excellent condition. I replaced the brushes and bearings. One bearing needed replaced. Good used parts are available. You could get a whole setup including adaptor and controller for under 2K. Have a look around. You will find a decent motor that has been in an EV. Forklift motors are fine if you find the right ones and find it in good condition. Your best off finding a good use EV and part it out. They are around and more of them than you might think. Don't just buy the first so called deal that surfaces. Be sure of what you want first. Know the type of car you want to convert and then go hunt for a setup that will work. You may need a different adaptor. If you go with the Kostov and you decide on an S-10 Pickup I have an adaptor that will fit for cheap and is in good condition.


Pete :)
 

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The regen issue would also depend on the terrain where you are driving. If you have a lot of hills then it may be useful to regen to save the service brakes when decending long slopes as well as making up some of the energy getting up there in the first place.

However, regen slows you down and that means that you have to use energy to maintain speed.

I thought regen might help my build as my commute is on either side of a big hill. Now I think regen will cost me in speed, and free speed at that.
Even in my ICE car, once I have crested the hill I can drop into neutral and almost coast all the last 10 miles into work were it not for a couple of roundabouts in the way.
 

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Discussion Starter #6
Pete and Woods, thank you both. Actually, Pete, I already own the car I want to convert. I wish I could take you up on the offer of an S-10 trans adaptor, though.

Woods, the hill thing is the exact reason why I want regen braking. I don't expect to regain any large amount of energy, but it sure is more comfortable to me to have a steady retardation available on a long downhill without riding the brakes. Like you, I coast like a maniac. But the terrain here in western Colorado USA has been cleverly designed with sharp turns in the middle and bottom of all the good coasting runs. When I must slow, I'd rather charge the battery than drag the brakes.

Pete, where I live, fork lift boneyards are unheard of. It ain't the middle of nowhere, although you can see it from here. But your advice to keep my eyes open is well taken.

Dan
 

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However, regen slows you down and that means that you have to use energy to maintain speed.
Hi Wood,

I don't get it. If you're maintaining speed you are either motoring (like on the flat) or generating (like on the downhill). But never both at the same time. And with regeneration capable systems, you just use regen when you want to.

I thought regen might help my build as my commute is on either side of a big hill. Now I think regen will cost me in speed, and free speed at that.
If you have a decent system, you can set it up to give you a pure coast mode. I prefer it this way and is why I put the regen input command pot on the brake pedal. So if I remove my foot from both pedals, I just coast. I also install a regen adjustment pot on the dash which allow me to set the maximum braking torque and can turn off regen completely. This allows adjustment for various road conditions.

major
 

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Discussion Starter #9
Major,
Thank you - that is the kind of regen control I envision, there when you want it, gone when you don't. I would appreciate it if you could take a look at the attached file, which is a performance chart for the Kostov 168 volt sepex motor, as presented on the kostov-motors.com website.

I am gathering from this chart that the field current is about 2.4% of the armature current. Do I have this right? The max field shown on the chart is 12 amps, for 500 amp armature. Is there a need to energize the field beyond the 2.4% rule?

I'm also thinking that the voltage needed to achieve typical field currents is quite a bit less than, say, 144v. Depending upon the field resistance, of course.

Your comments welcome.

Dan
 

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Discussion Starter #10
And I forgot, one more question: is it even reasonable to contemplate regeneration of a 144v battery pack with a brushed DC motor with interpoles? I keep reading about commutator fireballs, etc.

Dan
 

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I am gathering from this chart that the field current is about 2.4% of the armature current. Do I have this right?
Hi Dan,

Yeah, that's the way I read it. By keeping the field current (If) proportional to armature current (Ia), they emulate series motor performance. Of course, to take advantage of the SepEx, you would vary the field current differently over portions of the operating region for speed control, usually down around the 60 minute rating and below (load wise).

The max field shown on the chart is 12 amps, for 500 amp armature. Is there a need to energize the field beyond the 2.4% rule?
Yes, at higher armature current for example. *Also, in the normal operation, you would likely control the field current such that it rarely is 2.4%Ia. The 2.4% was just a condition which the motor manufacturer chose to use to depict motor performance on that particular graph.

I'm also thinking that the voltage needed to achieve typical field currents is quite a bit less than, say, 144v.
I would imagine voltage to get those indicated field currents would be a lot less than 144.

And I forgot, one more question: is it even reasonable to contemplate regeneration of a 144v battery pack with a brushed DC motor with interpoles? I keep reading about commutator fireballs, etc.
Sure it is reasonable. That's why they use interpoles. You should be able to operate forward, reverse, motor or generator without commutation difficulty up to the allowable voltage and current limits.

I guess the tricky part is finding or building a controller for this motor :)

major
 

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Hi Wood,

I don't get it. If you're maintaining speed you are either motoring (like on the flat) or generating (like on the downhill). But never both at the same time. And with regeneration capable systems, you just use regen when you want to.
major
Ahhh, sorry, rushed post as I was getting ready to go out to work.

What I mean is that by coasting I can crest a hill at 40mph and coast down it gaining speed, up to 70+mph, then ride the rest of the smaller hills like a roller coaster without needing any more power. If I were to regen or engine brake then I would reach the bottom of the first hill slow and need to power up the next one losing any benefit gained from gravity.
So, depending on the terrain, regen may not be the most suitable thing to use.
 

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Discussion Starter #13
Hello Major,
Most of what I've picked up regarding sepex motor control has been from your posts. I think I've combed through all of 'em. Thanks for taking the time with my request.
... Of course, to take advantage of the SepEx, you would vary the field current differently over portions of the operating region for speed control, usually down around the 60 minute rating and below (load wise).

... Also, in the normal operation, you would likely control the field current such that it rarely is 2.4%Ia. The 2.4% was just a condition which the motor manufacturer chose to use to depict motor performance on that particular graph.

I guess the tricky part is finding or building a controller for this motor :)

major
Heh. Tricky indeed, and it is becoming more apparent why. It looks like a sepex controller needs to be a one-off for a specific motor, or else so flexible/programmable that it is liable to hideous errors by the user.

Just tell me the truth, is this science or art? :confused:

Dan
 

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Heh. Tricky indeed, and it is becoming more apparent why. It looks like a sepex controller needs to be a one-off for a specific motor, or else so flexible/programmable that it is liable to hideous errors by the user.

Just tell me the truth, is this science or art? :confused:
It is science. But not near as easy as mating a series motor to an oversized chopper :)

What is really needed is a SepEx motor controller with an Auto Tune feature. And I don't think that is out of the question. We just need that Tesseract and Qer team to get busy on it ;)
 

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It is science. But not near as easy as mating a series motor to an oversized chopper :)

What is really needed is a SepEx motor controller with an Auto Tune feature. And I don't think that is out of the question. We just need that Tesseract and Qer team to get busy on it ;)
Hey Tesseract,
Did you ever figure out if the interpole inductance is adequate to keep the Soliton happy?
Gerhard
 

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What is really needed is a SepEx motor controller with an Auto Tune feature. And I don't think that is out of the question. We just need that Tesseract and Qer team to get busy on it ;)
Hey maj - wouldn't auto-tune, in this case, only be able to determine the inductance and resistance of field and armature, but not the number of comm bars, etc., that also affect the behavior of the motor?

Anyway, the real problem with sepex is akin to that with series regen - protecting against "unwise" choices by the customer resulting in destruction of the motor and/or controller.


Hey Tesseract,
Did you ever figure out if the interpole inductance is adequate to keep the Soliton happy?
Gerhard
Nope. We don't currently have any motors at the shop with interpoles that fit on our dyno.
 

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Hey maj - wouldn't auto-tune, in this case, only be able to determine the inductance and resistance of field and armature, but not the number of comm bars, etc., that also affect the behavior of the motor?
Hi Tesser,

I am talking about an Auto-Tune sequence, or procedure, similar to that which I have used on industrial VFDs when setting them on an induction motor. The motor is connected to the controller which is connected to the appropriate power supply. The motor shaft is empty; no load has been attached to the motor. The drive (VFD) is turned on and through a user interface, handset or computer, from a menu, Auto-Tune is selected. The user then enters motor nameplate data and presses the start key.

The VFD then takes about 2 or 3 minutes and sequences through a bunch of tests which include rotation of the motor. It completes the Auto-Tune and signals the user. During this process, the VFD has adjusted parameters which it stores and uses for proper control (Flux Vector or FOC) of the motor in normal operation.

Now to manually tune a SepEx controller for a motor, I have to figure out a field map so I can manually enter certain parameters along with resistance and inductance. As you are aware, I prefer to run the motor and measure the magnetization or saturation curve, if field performance data is not available from the motor manufacturer. IIRC, you had figured out some method to approximate such data before I posted my method. Point is, there are several methods to learn what is needed. And I don't think the human being is necessarily required in the process ;)

It may need some simple user input such as basic nameplate data, but I have never had to count the comm bars to do it :) And I could see the Auto-Tune process being easier and more accurate if the motor was equipped with a RPM sensor. I am pretty sure a couple of dorks and nerds could figure out how to make a machine do it :D

maj
 

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Discussion Starter #19
It seems to me that a sepex controller would need to know the RPM of the motor, to know when to reduce the field strength. Is this so?
 

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I have an 11 inch Kostov Sepex. It is great fun. You can get some low power controllers by Kelly and Curtis (around 50 kW). If you want more power, like the series controllers have, you are on your own.

My motor was rewound, so my numbers might not match a stock Kostov. My motor gets pretty hot after 10 minutes on 48V input with the stock input fan. Since my field has R = 1 Ohm, this is about 48 Amps on the field. Things should be better once I get my electric blower hooked up helping cool the motor. It'll be even better once I get my homebrew controller v2.0 finished (version 1.0 worked great... for about an hour... :cool: I'll post that adventure soon.). I have only run on 48 to 96 V so far, but I'm seeking to go much higher. You ramp up the field current for lower rpm or more regen, and weaken the field to speed up, so in real operation you'd rarely be fixed to 2.4% field.

I agree, you don't really need regen... I agree it only adds a little to your range... But there is something so awesome about doing regen. It's a special feeling knowing you are pumping electricity into your batteries, instead of heating up your brakes. This feature seems to really impress passengers, EVers and non-EVers alike. I can get skid-the-wheels powerful regen. Regen has a couple of other benefits for me:

  • I can tow my car behind a truck, and via regen recharge at 50+ kW! That's four times the rate of a 240V plug! This is handy for quick recharges for racing, or could come in handy if I run out of charge -- any car can tow me a little ways and get me going again. I believe it is much greener to use a modern emissions controlled truck than using a typical dirty dedicated generator.
  • I have no BMS, yet the batteries stay very balanced. With 50 Amp regens, the batteries drift about 0.5 V apart in just a handful of cycles. With a small number of big shots of regen per drive (I don't know exact numbers yet, I'd guess something like 200 or 300 Amps) the batteries stay within about 0.02 V of balanced.
Cautions:

  • I have Optima Blue Tops that can handle large charging currents
  • Tow regen might blow up a low power sepex controller
Major,
Thank you - that is the kind of regen control I envision, there when you want it, gone when you don't. I would appreciate it if you could take a look at the attached file, which is a performance chart for the Kostov 168 volt sepex motor, as presented on the kostov-motors.com website.

I am gathering from this chart that the field current is about 2.4% of the armature current. Do I have this right? The max field shown on the chart is 12 amps, for 500 amp armature. Is there a need to energize the field beyond the 2.4% rule?

I'm also thinking that the voltage needed to achieve typical field currents is quite a bit less than, say, 144v. Depending upon the field resistance, of course.

Your comments welcome.

Dan
 
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