Soapbox on regenerative braking

Technical discussion on converting internal combustion to electric
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Johny
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Soapbox on regenerative braking

Post by Johny » Tue, 16 Jun 2009, 15:30

Gow864 wrote: I suppose that you've all seen these AC induction would the 18hp push a Barina along? Image

In a nutshell - no. Torque starts dropping off at 750RPM so its an 8 pole motor. I make it a 6.25kW. That's enough to maintain 75k/h on flat and level. I guess with a gearbox it could be enough for a city car runabout.
All this of course is just my opinion.

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Soapbox on regenerative braking

Post by acmotor » Tue, 16 Jun 2009, 16:52

Neville, Yes it is all DC (or is that AC) in some way or another !!!!
Good job there bringing us together again !
We are all in the same boat (just some boats still have oars) Image
Come on guys lighten up. They are all EVs. We just need to recognise their relative strengths and weaknesses.

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Soapbox on regenerative braking

Post by Richo » Tue, 16 Jun 2009, 18:39

Peace my Brothers Image


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Soapbox on regenerative braking

Post by Nevilleh » Fri, 19 Jun 2009, 13:08

Yes, this thread started with regen!
I read the stuff in the link someone posted earlier, written by the Zilla man and he certainly went into it very thoroughly. The problem of arcing at the brushes due to either field/armature current imbalance or changes in the brush timing was something I didn't know about before.
The principle of putting a small current pulse through the thing to get the field excited is pretty obvious though, but I need to read some more to understand how he was using the Curtis controller. I would've thought that leaving the controller shut off and putting the generated current into a boost converter charging the battery would do the trick.
Interesting that he claimed an "8% to 15%" improvement in range. That's like adding 8% to 15% more battery capacity. Say 10% average. So if I have $10,000 worth of batteries, I could spend another $1000 either on regen or just batteries. If I can do regen for less than $1000, I am ahead!

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Soapbox on regenerative braking

Post by Goombi » Fri, 19 Jun 2009, 13:45

I don't belive Curtis and Series motor will deliver REGEN anyhow.
The information is not correct

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Soapbox on regenerative braking

Post by antiscab » Fri, 19 Jun 2009, 21:45

Goombi wrote: I don't belive Curtis and Series motor will deliver REGEN anyhow.
The information is not correct


a stock curtis 1231C wont do regen (and many other things) you are correct.
Otmar was fixing curtis controllers long before he starting making the zillas. Otmar modified the curtis (and the surrounding system) to do regen.

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Post by acmotor » Sat, 20 Jun 2009, 08:39

Sorry, it must be said... Claytons regen.
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Post by zeva » Sat, 20 Jun 2009, 09:16

Well I think everyone agrees that commutated motors have a limited lifespan and will only be around while they offer a significant cost and/or simplicity advantage. Despite my original rant, I would quite like to have regen on my next EV. Mostly to save wear on my brakes, in truth!

So I guess those of us involved with EV R&D should be doing our best to bring the price of induction and PMSM/BLDC technologies down. Rod Dilkes has been testing a nice BLDC kit (similar size to the Azure Dynamics AC24) which seems promising, though from memory it's still around the $8K mark for motor & controller.

I see Kelly has a 144V 250A BLDC controller now for a very reasonable $1K, but that's still only half the power of the old ubiquitous Curtis 1231 DC controllers.. So a bit underwhelming for a road-going car.

Plenty of cheap industrial AC induction motors around, though they're usually too big & heavy to fit in compact FWD engine bays. Maybe we could contract a manufacturer to build something more appropriate for EVs (e.g more compact, lighter housing, higher RPM rating, possibly water cooled?).

I purchased a few AT90PWM3 micros recently and look forward to having a play with them. These little chips have 6x PWM out, i.e able to drive three half bridges with adjustable dead time, so are well suited to induction or BLDC motor control. Worst case it'll be an interesting learning experience, best case maybe one day I'll be able to build an AC/BLDC EV controller!
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Soapbox on regenerative braking

Post by Squiggles » Sat, 20 Jun 2009, 14:48

There is some really interesting PICs from Microchip as well.
Like dsPIC33FJ64MC506

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Soapbox on regenerative braking

Post by coulomb » Sat, 20 Jun 2009, 15:56

zeva wrote: Well I think everyone agrees that commutated motors have a limited lifespan and will only be around while they offer a significant cost and/or simplicity advantage.
Ok, but I think that DC will be around for a while yet.
So I guess those of us involved with EV R&D should be doing our best to bring the price of induction and PMSM/BLDC technologies down.
I've never understood why separately excited DC isn't more popular. Is it that the motors are less common? A quick look through the EV Album indicates that they are mostly European conversions. Kelly make controllers for them, so it can't be a lack of controllers.

It seems to me that separately excited motors offer the economy of DC, yet with reasonably easy regen. Is it the arcing at the commutators? Maybe that you need to tell the controller about the field characteristics... but surely that's a bit of research and/or experimentation, and plugging in a few numbers into the controller somehow?
Plenty of cheap industrial AC induction motors around, though they're usually too big & heavy to fit in compact FWD engine bays.
I don't know about that. There are plenty of circa 7.5 kW 132 frame motors around, I think. But we need the technology for rewiring for lower voltage, so we can take advantage of the low voltage controllers out there: Kelly, and hopefully soon Tritium. The controllers are where the AC bottleneck is, I feel. Over AU$10K for a 100 kW controller isn't going to attract too many conversions. Even the 50 kW controllers are expensive, or difficult to scrounge.
Maybe we could contract a manufacturer to build something more appropriate for EVs (e.g more compact, lighter housing, higher RPM rating, possibly water cooled?).
I don't think we need water cooled. Lower voltage windings and balanced for 6000 RPM are all we really need, unless we want permanent magnets. I suspect that local manufacturers might not be set up for PM. PM seems to offer two main advantages: higher efficiency and less torque (hence power) drop off at higher speed.
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Soapbox on regenerative braking

Post by Goombi » Sat, 20 Jun 2009, 16:43

REGEN or not REGEN

DC separated traction motor. The difference from series motor is to use controllers to control and adjust the field coil and the armature coil separately, and the motor still have perfect mechanical property and speed regulation performance.. By increasing the controller’s set, it can realize the follow function: 1) To set speed limit running 2) To prevent backward slipping when uphill 3) To recycle energy using the regenerative braking principle when downhill and deceleration.

With every Regen type Motor includes a programmer for Controller I am unable to copy the pdf file here. Buying the Regen Unit will come setup with standard calibration. You can adjust to personal preferences The only diference between Regen and series motor is the price around $300-500 aud More. Go to my website amd log on Regen Also how to make EV in 3 days Go to "Ideas."

Anyone interested in the PDF Programmer file send me your email
Last edited by Goombi on Sat, 20 Jun 2009, 06:52, edited 1 time in total.

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Soapbox on regenerative braking

Post by Nevilleh » Sat, 20 Jun 2009, 17:02

Suppose I disconnect the motor from the controller when I want to do regen, connect it to a boost converter (maybe a changeover contactor)and stick a current pulse through it to generate enough field for it to start generating. The boost converter o/p has a voltage higher than the battery - say # of cells x 3.6 - and it is fed to the battery with a variable current control. The motor should keep generating as long as the converter draws enough current from it to keep enough field going.
In general terms, why wouldn't that work?
Keeping the field and armature currents the same ie they're in series, should not cause any problems with brush timing and hence arcing.
Controlling the converter o/p current would vary the degree of braking.

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Soapbox on regenerative braking

Post by Squiggles » Sat, 20 Jun 2009, 17:36

Series motor regeneration.
There seems to be three issues with using a series motor for regen.
1. Field winding has to be reversed with respect to motor.
2. A voltage boost principle has to be employed.
3. Some excitation current may be needed to start generation, there is a remote possibility that residual magnetic flux may be sufficient.


Sepex motors,
It appears that in general sepex motors have lower ratings for physical size compared to series motors. This is probably because the field currents are lower. To get the equivalent output the field has to have the same current as the rotor, this means that controllers have to have two high power drive stages which of course adds cost.
They certainly provide advantages in terms of speed control and regen.

Kostov lists sepex motors on their website. Unlike their series motor range very little is provided in terms of specification.

In my opinion sepex DC is likely to be a superior option to series DC for EV if the kit was available at appropriate kW/Nm ratings and $s (appologies to Goombi, one supplier is not enough to support an industry, two many eggs one basket :) ). Ultimately AC or BLDC is likely to be the best, it is only economics that prevents this at the moment.

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Post by Nevilleh » Sat, 20 Jun 2009, 18:05

Not sure why you say the field winding has to be reversed?
If the motor is being driven CW, it is producing a back emf to counter the applied voltage ie the same polarity, isn't it? So if I remove the drive voltage, surely that back emf which is the generated voltage stays the same?

Interesting to calculate the energy!

= 1/2 mv^2 so for a 1500 kg vehicle at 27.8 m/s, E = 1.16 Mj.
If I absorb that at a rate of say 10 seconds to come to a complete halt, I get 116 Kw! My boost converter is going to have to be pretty big....

I wonder if it would be possible to switch the controller off and just connect a big load resistor to the motor? As long as the current kept flowing, it would still generate, wouldn't it? The resistor could absorb 100 Kw for 10 seconds - I think!
No energy saving, but saves your brake pads.

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Post by Goombi » Sat, 20 Jun 2009, 18:16

No hard feelings Squiggles.. May the best eqipment win. All Regen motors and controller go on Test bench in China before sending. I fail to comprehend , how anyone can buy a Regen Motor and off the shelf controller to match. If this chinese Regen is working and at very reasonable prices and delivery Why would anyone wish to experiment with the unknown?
But --- some mothers do have them..

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Post by Squiggles » Sat, 20 Jun 2009, 18:17

Nevilleh wrote: Not sure why you say the field winding has to be reversed?
If the motor is being driven CW, it is producing a back emf to counter the applied voltage ie the same polarity, isn't it? So if I remove the drive voltage, surely that back emf which is the generated voltage stays the same?


Only because it is commonly stated in the reading I have been doing, every working example seems to have done it.

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Post by Nevilleh » Sat, 20 Jun 2009, 18:23

Squiggles wrote:
Nevilleh wrote: Not sure why you say the field winding has to be reversed?


Only because it is commonly stated in the reading I have been doing, every working example seems to have done it.


I just tried it with a small, permanent magnet motor and the generated dc is the same polarity as the applied voltage when I spin it in the same direction. As you would expect really. Can you give me a reference to what you read where they reverse the field winding?

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Post by Squiggles » Sat, 20 Jun 2009, 18:23

Goombi wrote: No hard feelings Squiggles.. May the best eqipment win. All Regen motors and controller go on Test bench in China before sending. I fail to comprehend , how anyone can buy a Regen Motor and off the shelf controller to match. If this chinese Regen is working and at very reasonable prices and delivery Why would anyone wish to experiment with the unknown?
But --- some mothers do have them..


Don't get me wrong, I have no problem with what you are supplying, the more the merrier. There is plenty of good kit coming out of China (along with some rubbish :( ). But even if the gear you are sourcing is the very best technology available I would still be nervous if no one else is manufacturing similar stuff.

It is just my nature to experiment, invent or innovate. After all that is how progress is made.

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Post by Squiggles » Sat, 20 Jun 2009, 18:38

Nevilleh wrote: Can you give me a reference to what you read where they reverse the field winding?


They are littered through these forums, I will see if I can find some.

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Post by Squiggles » Sat, 20 Jun 2009, 18:40

Nevilleh wrote:
I just tried it with a small, permanent magnet motor and the generated dc is the same polarity as the applied voltage when I spin it in the same direction. As you would expect really. Can you give me a reference to what you read where they reverse the field winding?


The fields don't reverse in the PMs, that might have something to do with it.

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Post by Nevilleh » Sat, 20 Jun 2009, 18:44

Ah, a bit of further thought tells me that when generating, the current flow through the armature is reversed, so if the field winding is still connected the same, the magnetic field will also be reversed and that's not what we want to happen. So the field connections have to be reversed so the magnetic field direction stays the same and allows the armature current to reverse.
I should've thought it through before spouting on here!

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Post by Squiggles » Sat, 20 Jun 2009, 18:50

Yep, mind you I have no problem confusing myself.

Passed through Tauranga on the way to Whangamata from Rotorua in January. Not a bad place you got there.

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Post by Nevilleh » Sat, 20 Jun 2009, 21:28

Squiggles wrote:

Passed through Tauranga on the way to Whangamata from Rotorua in January. Not a bad place you got there.


Yes, it's pretty nice, best town in New Zealand! (Not biased or anything)

But still thinking of simple, regen braking and mainly to save brake wear rather than putting energy back into the system (viva Zeva!) I wonder what would happen if I just connected a load straight across the motor and then turned off the drive? The current flow would reverse, the field current would go through zero, would the reduction in magnetic field strength cause it to stop generating? Or would there be enough residual magnetism to get it generating the opposite way?
Might be a possibility.

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Post by Squiggles » Sat, 20 Jun 2009, 22:54

I had exactly the same thought about the field current passing through zero. An experiment might find the answer.

Drive off, braking resistance on. Precisely what is down in diesel electric locomotives. Huge fans to cool resisters, stopping 5,000,000 kgs from 80kph is probably a reasonable amount of energy to dissipate!!

I tell you what, driving around your area you need all the braking you can get. I reckon the road to Waihi might have 15km with the longest straight section about 60m! and then there are the hills. Come to think of it, you really do need regen battery charging. Your range would have to seriously limited by the terrain.

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Post by acmotor » Sun, 21 Jun 2009, 03:26

What sort of emotor do they run in diesel electric locos ? Does following their format help any ? if they deal with big regen.
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