# Noob with sepex fixation



## Guest (Oct 10, 2010)

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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## Dan Hawkins (Jan 3, 2010)

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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## Guest (Oct 10, 2010)

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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## Woodsmith (Jun 5, 2008)

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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## Dan Hawkins (Jan 3, 2010)

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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## major (Apr 4, 2008)

Woodsmith said:


> 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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## Guest (Oct 10, 2010)

Thanks Major I was going to respond, now I don't have to do that.


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## Dan Hawkins (Jan 3, 2010)

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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## Dan Hawkins (Jan 3, 2010)

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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## major (Apr 4, 2008)

Dan Hawkins said:


> 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.



Dan Hawkins said:


> 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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## Woodsmith (Jun 5, 2008)

major said:


> 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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## Dan Hawkins (Jan 3, 2010)

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. 


major said:


> ... 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.
> 
> ...


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? 

Dan


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## major (Apr 4, 2008)

Dan Hawkins said:


> 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?


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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## GerhardRP (Nov 17, 2009)

major said:


> 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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## Dan Hawkins (Jan 3, 2010)

major said:


> 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


Yah. What he said! 

Dan


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## Tesseract (Sep 27, 2008)

major said:


> 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. 




GerhardRP said:


> 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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## major (Apr 4, 2008)

Tesseract said:


> 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 

maj


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## Dan Hawkins (Jan 3, 2010)

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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## DavidDymaxion (Dec 1, 2008)

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...  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



Dan Hawkins said:


> 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?
> ...


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## major (Apr 4, 2008)

Dan Hawkins said:


> 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?


No, most don't. I have seen it available as an option where the system would require tight speed regulation. But vehicles just run in torque control and let the human be the speed regulator


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## Dan Hawkins (Jan 3, 2010)

Hi Major,

I get that the right foot is a torque demander. But how does a sepex controller sort out whether a mashed pedal is because the driver (a) wants to lay rubber across the intersection when the light turns, or (b) wants that last 5 mph of top speed? 

The field strength needs to be different between these two situations, yes? It seems like the main variable here is motor speed, and the resulting back EMF. Oh, my head. 

Dan


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## samborambo (Aug 27, 2008)

Dan Hawkins said:


> 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?


Yes.

For a fixed field strength, all motors have a torque constant, Kt and a BEMF constant, Kv. Kt is the linear relationship between armature current and torque. Kv is the linear relationship between BEMF (the voltage developed by the motor as it rotates) and speed. 

Such motors having a fixed field are BLDC (since it has permanent magnets, the field is fixed), wound rotor synchronous AC with constant rotor current or a sepex with constant field current. 

Having a variable field strength means that Kt and Kv are no longer constant. For instance, increasing the field strength reduces Kt but increases Kv. This has a few advantages. You can now boost the BEMF at lower speed to reduce the amount of current required to produce the same torque. Conversely, you can reduce the BEMF to increase the current/torque available at higher RPM but I think you'd be restricted to how fast your commutator may run stably. Also the efficiency should increase at lower speed with a BEMF boost since there's less current going through the main controller, meaning less I2R losses in the MOSFET/IGBT and passive devices.

For you field control device, you could use a small micro like an 8 bit PIC or AVR powering a 25A/250V MOSFET through an isolated gate driver. Even an Arduino board may be powerful enough and would provide a shortcut for sorting out some of the sensor, control and PWM issues. I would design it so that the field control device receives the throttle signal and then controls the armature controller. I can imagine there would be a fair few PID regulators and a couple of other tunable parameters to contend with but it wouldn't be insurmountable. I suggest you study a bit more on the motor theory to get a handle on what the control scheme needs to do.

It would be quite an interesting project to create a sepex "add-on" device. Start it as an open source project and you may get the support of other engineers chipping in on design and programming. 

Sam.


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## major (Apr 4, 2008)

Dan Hawkins said:


> I get that the right foot is a torque demander. But how does a sepex controller sort out whether a mashed pedal is because the driver (a) wants to lay rubber across the intersection when the light turns, or (b) wants that last 5 mph of top speed?


Hi Dan,

Answer is that the controller does not have to know speed when in torque mode. A command (via the go pedal) to increase torque is independent of speed, up to the maximum limits of the system, which is 100% voltage to the armature and minimum field current considering the armature current at the instant, hence the required field map. Obviously the field controller has to communicate with the armature controller to accomplish all this. And all the while, it has to limit armature current.

Now even without speed feedback from the controller, good SepEx controllers are able to limit speed by monitoring the voltage, current and field current. So the ones I used for the IUVs would have a valet mode and reverse speed limit much slower than normal forward travel. But this is approximate. It worked very well. But for applications like a process control where precise speed regulation is needed, then a feedback is required.

I mentioned in the response to Tess because I envision tuning to be simpler having a speed sensor. But I don't think it is needed for EV operation. However, if it was already there, it may come in handy 

major


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## Dan Hawkins (Jan 3, 2010)

samborambo said:


> For you field control device, you could use a small micro like an 8 bit PIC or AVR powering a 25A/250V MOSFET through an isolated gate driver. Even an Arduino board may be powerful enough and would provide a shortcut for sorting out some of the sensor, control and PWM issues. I would design it so that the field control device receives the throttle signal and then controls the armature controller. I can imagine there would be a fair few PID regulators and a couple of other tunable parameters to contend with but it wouldn't be insurmountable. I suggest you study a bit more on the motor theory to get a handle on what the control scheme needs to do.
> 
> It would be quite an interesting project to create a sepex "add-on" device. Start it as an open source project and you may get the support of other engineers chipping in on design and programming.
> Sam.


Yes Sam, it would be. I'm more inclined to make the "add-on" micro board function as an administrator between two off-the-shelf controllers, rather than reinvent a field controller. 

This "add-on" would accept inputs from the driver, armature current, field current, motor speed, and ?? It would generate two 0-5v PWM outputs to operate the controllers through their throttle pot connections. 

Some may tear their hair at this notion. But, there is presently NO controller capable of matching the Kostov 11 HV sepex motor that is on the market right now, begging for a ride. 

This is a DIY community, after all.


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## pm_dawn (Sep 14, 2009)

Hi !

What about this one:
http://www.coopercontrols.co.uk/components/evd90.htm

I know its not 500A but atleast it is 400A Peak.
It was used in the G-Vans

Best Regards
/Per


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## major (Apr 4, 2008)

pm_dawn said:


> What about this one:
> http://www.coopercontrols.co.uk/components/evd90.htm
> 
> I know its not 500A but atleast it is 400A Peak.
> It was used in the G-Vans


Hi /Per,

Dan's planned voltage is below the minimum for that unit. It appears quite large and no rating or price is given. It does show that such products have been made. I wonder why Kostov makes a motor when there is no available controller for it  Maybe Kostov knows of one.

Regards,

major


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## Dan Hawkins (Jan 3, 2010)

major said:


> Hi Dan,
> Answer is that the controller does not have to know speed when in torque mode. A command (via the go pedal) to increase torque is independent of speed, up to the maximum limits of the system, which is 100% voltage to the armature and minimum field current considering the armature current at the instant, hence the required field map. Obviously the field controller has to communicate with the armature controller to accomplish all this. And all the while, it has to limit armature current.
> 
> Now even without speed feedback from the controller, good SepEx controllers are able to limit speed by monitoring the voltage, current and field current.
> major


Major, I had quite a bit of trouble with the above, but I think a light is dawning. By monitoring the voltage applied to the armature versus the current it accepts, the back EMF can be known, and therefore the speed. 

Am I getting warm? 

Dan


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## Dan Hawkins (Jan 3, 2010)

pm_dawn said:


> Hi !
> What about this one:
> http://www.coopercontrols.co.uk/components/evd90.htm
> 
> ...


Hi Per,

Thanks for pointing this one out. It's probably not useful to me as its two bushel volume would take up a lot of space in my car. But it's good to know that such a controller has been built (and evidently still is available - but not sure from the website linked). 

Dan


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## major (Apr 4, 2008)

Dan Hawkins said:


> Major, I had quite a bit of trouble with the above, but I think a light is dawning. By monitoring the voltage applied to the armature versus the current it accepts, the back EMF can be known, and therefore the speed.
> 
> Am I getting warm?


Hi Dan,

No, you (or the controller) don't need to know the speed. That is the beauty of torque control. Regardless of speed, you want more torque, command it. It does not matter what the speed is.

Of course there are limits. Always limits  Like if your present speed is requiring all the available torque, you won't get any more by commanding it. But that "present speed" would be different depending on the headwind or grade. So really, you do not want the control system dependent on speed, except for maybe a cruise control option.

Regards,

major


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## Dan Hawkins (Jan 3, 2010)

Major, sir, your dogged determination to set me straight is really admirable. A few posts back, Samborambo advised me to study motor theory some more. I'll take that advice. Meanwhile, here's a hypothetical conversation between my throttle foot and the controller:

Foot: Gimmie torque.
Cont: That's all I got. 
Foot: C'mon, increase the field strength, that'll help. 
Cont: Hokay, boss, increasing the field strength.
Foot: You fool, that slowed me down. Weaken the field, like I said. 
Cont: You got it.
Foot: That slowed me down too. WTF?
Cont: Like I told ya, that was all the torque I got. The field strength was already optimum. 
Foot: OK, I admit it, but how did you know that? 
Cont: I was following the field map, like Major has been trying to explain to you. 
Foot: Oh. 

Dan


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## pm_dawn (Sep 14, 2009)

Hi !

I know i have posted about this controller before:
http://www.elektrosistem.com/e/p2.htm

They have two controllers that take 120v nom. The T82 with 800A peak and the smaller T62 (not shown in page) with 600A peak.

I know this car is using the T62.
http://www.diyelectriccar.com/garage/cars/214

Best Regards
/Per


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## DavidDymaxion (Dec 1, 2008)

Maybe they figure it is a case of "build it and they will come?" It's just a case of winding the fields differently, so it's not like it's a huge stretch to offer series and sepex.

It seems like a business opportunity to make a sepex controller that integrates with an automatic transmission. The problem is cheaper and simpler if you give up on taking off from 0 rpm and idle the motor.


major said:


> ... I wonder why Kostov makes a motor when there is no available controller for it  Maybe Kostov knows of one. ...


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## Dan Hawkins (Jan 3, 2010)

pm_dawn said:


> Hi !
> 
> I know i have posted about this controller before:
> http://www.elektrosistem.com/e/p2.htm
> ...


Thank you, Per. I have emailed the company with inquiries. 

Dan


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## samborambo (Aug 27, 2008)

DavidDymaxion said:


> Maybe they figure it is a case of "build it and they will come?" It's just a case of winding the fields differently, so it's not like it's a huge stretch to offer series and sepex.
> 
> It seems like a business opportunity to make a sepex controller that integrates with an automatic transmission. The problem is cheaper and simpler if you give up on taking off from 0 rpm and idle the motor.


What's the problem with taking off at 0 rpm? Sepex can adjust the field for a torque boost at lower rpm. In fact I wouldn't bother with a gearbox at all - just a fixed reduction ratio. Sepex motors combined with a smart controller are, in theory, one of the most dynamic types of motor. Compared to a series wound motor, they have increased torque ability and better efficiency at low RPM while also have an extended power region in high RPM. Technically, the only motor type that exceeds this versatility is an AC induction motor, mainly because the commutator doesn't limit power at high speed.

Sam.


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## samborambo (Aug 27, 2008)

I think you're right about the "build it and they will come" statement. I'm thinking that a controller with the field current power stage built in that compliments a tried and proven series DC controller would be a very attractive option. Since the power stage is handling a lot lower current, design should be a lot less demanding. If it were me working out a business model, I'd offer 6 different models. 150V and 300V at 25A, 50A and 75A.

By choosing a sepex motor over a series DC, you'd have many advantages:

Increased dynamic performance - no gearbox necessary.
Improved efficiency.
No reversing contactor required.
Regenerative braking - full four quadrant control.
With a bit more logic in software, you could support compound wound (sepex + series) motors as well.

Start it as an open source project and offer to build/sell the hardware. Although there's a lot of design and progamming to be done, the hardware would be fairly cheap.

Sam.


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## DavidDymaxion (Dec 1, 2008)

Taking off at 0 rpm is not a technical problem, obviously many controllers do that. I meant as a business case, you could build a cheaper controller if you gave up takeoff from 0 rpm, and let the motor idle.

This reduces the usable rpm range of the motor, so gears make up for that.

I'd think there would be interest in a controller that was 1/2 the price, yet very robust, high current, and with regen even with the limitation of having to idle.

My car is doing this now. On 48V it is very usable as a city car. I have only done a couple of 96 V tests so far, but think lower highway speed would be doable. You could build a controller like this for around $200 to $500 that would pass 1000+ Amps. Going to 144+ V is going to cost more, but still way cheaper than a Soliton or Zilla.


samborambo said:


> What's the problem with taking off at 0 rpm? Sepex can adjust the field for a torque boost at lower rpm. In fact I wouldn't bother with a gearbox at all - just a fixed reduction ratio. Sepex motors combined with a smart controller are, in theory, one of the most dynamic types of motor. Compared to a series wound motor, they have increased torque ability and better efficiency at low RPM while also have an extended power region in high RPM. Technically, the only motor type that exceeds this versatility is an AC induction motor, mainly because the commutator doesn't limit power at high speed.
> 
> Sam.


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## samborambo (Aug 27, 2008)

DavidDymaxion said:


> Taking off at 0 rpm is not a technical problem, obviously many controllers do that. I meant as a business case, you could build a cheaper controller if you gave up takeoff from 0 rpm, and let the motor idle.
> 
> This reduces the usable rpm range of the motor, so gears make up for that.
> 
> ...


David, I must be a little slow on the uptake here or not privvy to some secret design breakthrough - how is it cheaper making a controller that can't start a motor under load at 0 rpm?

Build a 1kA+ controller for under $500? You'd be lucky to get the power stage silicon and bulk storage capacitors for that.

Sam.


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## DavidDymaxion (Dec 1, 2008)

It would be hard to do a modern style controller that cheap, but you can do it old school. Just skip using power stage silicon and capacitors. I have done it. 

For $100, use a contactor with a sepex motor. That's what I did for a while on my car. On 48 V the motor idles at 1600 rpm, and you shift to change speeds. There's is no current limit. Pop the clutch in 5th gear and you'll draw 1000+ Amps. Downshift from 5th to 2nd and you'll get hundreds of Amps of regen.

For the < $500 "deluxe" controller, add a rheostat (or a small controller) to vary the field and ability to vary motor speed from 1600 rpm to 5000 rpm -- now you don't need to shift all the time. I did this, it was great fun (it broke after an hour, I still have to fix it, but the basic concept is sound). You can draw as many Amps as your motor or batteries or cables can take. There have been multiple old timer EVers that drove their cars this way.

For < $800 you can do switching from 48 V to 96 V with some additional contactors.

There are some fine details I'm leaving out for simplicity, but that's the basic idea. I wouldn't suggest starting a car in gear from 0 rpm with this setup (although that might work with an automatic). You'd get a huge current spike, and a huge jerk that could even spin the wheels. You start the motor in neutral and slip the clutch to get going. Here's some fun proof it works: http://explodingdinosaurs.com/9electric/2009saltflats/MVI_0308burningsalt.MOV 

This is crude. The pedal position commands speed more than torque (although that could be fixed with a microcontroller). You can't just buy it. It is, however, cheap and gives you regen and gives you thousands of Amps.


samborambo said:


> David, I must be a little slow on the uptake here or not privvy to some secret design breakthrough - how is it cheaper making a controller that can't start a motor under load at 0 rpm?
> 
> Build a 1kA+ controller for under $500? You'd be lucky to get the power stage silicon and bulk storage capacitors for that.


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## samborambo (Aug 27, 2008)

DavidDymaxion said:


> It would be hard to do a modern style controller that cheap, but you can do it old school. Just skip using power stage silicon and capacitors. I have done it.
> 
> For $100, use a contactor with a sepex motor. That's what I did for a while on my car. On 48 V the motor idles at 1600 rpm, and you shift to change speeds. There's is no current limit. Pop the clutch in 5th gear and you'll draw 1000+ Amps. Downshift from 5th to 2nd and you'll get hundreds of Amps of regen.
> 
> ...


Sounds very good. I missed the reference to the main controller just being a contactor.

A further refinement in order to allow controlled on load starting would be to have a small 0-100A PWM controller on the NC side of the contactor. Ramp up the field current for better starting torque under 100A. Once the motor passes, say, 1000RPM switch over to direct current from battery to armature and just use the field current to control power via armature current & voltage feedback.

Sam.


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## DavidDymaxion (Dec 1, 2008)

That's a good idea.


samborambo said:


> Sounds very good. I missed the reference to the main controller just being a contactor.
> 
> A further refinement in order to allow controlled on load starting would be to have a small 0-100A PWM controller on the NC side of the contactor. Ramp up the field current for better starting torque under 100A. Once the motor passes, say, 1000RPM switch over to direct current from battery to armature and just use the field current to control power via armature current & voltage feedback.
> 
> Sam.


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## DIYguy (Sep 18, 2008)

Dan Hawkins said:


> I keep veering toward the DC sepex motor. I like engine braking, so regen is attractive to me, because of the familiar feel.


How about this one Dan...  

Ya, I know... u need a controller. Maybe we should hack an industrial DC motor drive...like some guys have been doing with the AC ones...


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## Dan Hawkins (Jan 3, 2010)

DIYguy said:


> How about this one Dan...  Ya, I know... u need a controller. Maybe we should hack an industrial DC motor drive...like some guys have been doing with the AC ones...


DIYguy, thank you. That's intriguing, I have to admit. Is this motor in your possession? Do you know the weight/dimensions? And I have no idea what an industrial DC controller would look like. Probably big and err...industrial 

One drawback I see is that the motor is wired to run at 240 VDC (armature) at 2941 RPM. I think this means that obtaining higher speed would require significant voltage from the battery pack. 

It's great that there is so much information on the data plate. Since the field coils can be connected in series or parallel, does this mean that a parallel connection would more easily allow over-energizing the field by applying higher voltage for more starting torque? I hope Major is listening in 

Dan


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## Dan Hawkins (Jan 3, 2010)

Dan Hawkins said:


> ... the motor is wired to run at 240 VDC (armature) at 2941 RPM...
> Dan


Phooey, I meant 2491 RPM like it says on the data plate 

Dan


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## DavidDymaxion (Dec 1, 2008)

Nah, just weaken the field for more rpm.


Dan Hawkins said:


> ... One drawback I see is that the motor is wired to run at 240 VDC (armature) at 2941 RPM. I think this means that obtaining higher speed would require significant voltage from the battery pack. ...


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## major (Apr 4, 2008)

Dan Hawkins said:


> Since the field coils can be connected in series or parallel, does this mean that a parallel connection would more easily allow over-energizing the field by applying higher voltage for more starting torque?


Hi Dan,

Sure, that would get you 2 to 1 over excitation. Most of the purpose SepEx motors go much higher, like 10 to 1. But that is what you put up with using a shunt motor. And how much you think it weighs?

major


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## Dan Hawkins (Jan 3, 2010)

major said:


> ... And how much you think it weighs?
> major


I'm looking at those welded-on lifting eyes and thinking...a bunch. The red warning label pasted on the motor probably says something like "Don't even think about it." 

Dan


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## DIYguy (Sep 18, 2008)

Dan Hawkins said:


> DIYguy, thank you. That's intriguing, I have to admit. Is this motor in your possession? Do you know the weight/dimensions? And I have no idea what an industrial DC controller would look like. Probably big and err...industrial


I could own it easily if I wanted. I could measure it if you want. It's probably 11" dia and 20" long...just guessing. Likely weighs 200 lbs or maybe a bit more. Industrial motor controllers tend to big and ugly...depending on hp. I think this one was driven with an AB 1395 if I'm not mistaken.



Dan Hawkins said:


> One drawback I see is that the motor is wired to run at 240 VDC (armature) at 2941 RPM. I think this means that obtaining higher speed would require significant voltage from the battery pack.





Dan Hawkins said:


> It's great that there is so much information on the data plate. Since the field coils can be connected in series or parallel, does this mean that a parallel connection would more easily allow over-energizing the field by applying higher voltage for more starting torque? I hope Major is listening in
> Dan


Ya, likely weakening the field will get higher rpm.... I'll let Major comment here. The industrial DC motor controls let you program a lot of parameters. 

It would be nice to see someone do a clean Sep-ex application. These motors (if you get the right one) have some nice characteristics.


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## DavidDymaxion (Dec 1, 2008)

These are anecdotal, but interesting to see some folks observed better performance from sepex systems with lower voltage than series systems with higher voltage:

http://www.mail-archive.com/[email protected]/msg02513.html

http://www.mail-archive.com/[email protected]/msg02671.html

http://www.mail-archive.com/[email protected]/msg02667.html


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