Soapbox on regenerative braking

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

Post by acmotor »

You could always use your brakes. Image
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Post by Johny »

Your what?

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Post by bga »

Resistors... paah! (or what about those steel and ex-asbestos thingies)

"...and Chrysler still has some bugs to work out with its EV platform. Right now the regenerative braking bites right away, instead of letting the car coast, requiring constant use of the accelerator to keep moving, but Chrysler is working on it."
Jeez, you'd think that wouldn't be very hard to get right!

I think that some mode control may be desirable to that the engine braking (regen)) can be modified according to the traffic situation. Perhaps some amount of deadband to allow coasting to be achieved could be part of the settings.
In an ICE, the gear porition kind-of does this, auto gearboxes more so.

I was contemplating an analog knob that allows the mode and strength to be smoothly set.

Monitoring the brake pedal position (or hydraulic pressure?) makes good sense and is likely necessary to allow the regen to be phased out as more mechanical brake is applied so that a drive-end skid can be avoided.
This may be complicated by some brake designs, I drove a camry where the brakes activated on the slightest pedal movement. I suppose it stops the drivers riding the brake pedal.

If there is significant regenerative braking, the brake lights should be lit to reduce the chances of a rear-ender. It may be necessary to integrate this into the controller so that it's automatic.

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Post by coulomb »

acmotor wrote: You could always use your brakes. Image
Oh, I don't like using them because it wears the brake pads down.

Cue the Monty Python sketch: Cranky old lady is looking for her glasses, which are on her head. Basil tries to tell her and points to her head, but she can't seem to hear him. Eventually Basil realises that she doesn't have her hearing aid turned on, and jumps up and down telling her to TURN IT ON!. She says "I don't turn it on because it wears the batteries down!"

To finish the joke, she turns it on anyway to see what all the fuss is about. Now Basil starts to pretend to me making a long speech, gesticulating grandly but making no sound. She says "wait a minute, wait a minute, I'll turn it up..."

Well, we all know the ending.   Image

Edit: on -> turned on
Last edited by coulomb on Tue, 21 Jul 2009, 10:56, edited 1 time in total.
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Post by Squiggles »

bga wrote: Resistors... paah! (or what about those steel and ex-asbestos thingies)


If there is significant regenerative braking, the brake lights should be lit to reduce the chances of a rear-ender. It may be necessary to integrate this into the controller so that it's automatic.


10kW of brake lights should get the message across.

I still think an electric kettle full of water would be good for regen, when the trip is finished you can make yourself a nice cup of tea.

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Post by Johny »

coulomb wrote:Cue the Monty Python sketch: Cranky old lady is looking for her glasses, which are on her head. Basil tries to tell her...
Hah - technical error. Basil is the character from Fawlty Towers NOT Monty Python (silently hopes that the Basic character wasn't developed during Monty Python era).
This thread is deGENERATing.
Last edited by Johny on Tue, 21 Jul 2009, 16:50, edited 1 time in total.

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Post by weber »

Tritium_James wrote: Weber, with that setup most of the load would be dissipated as heat anyway, halogen floodlamp tubes are only something like 6 or 8% efficient at electricity -> light, the rest is heat. So you might as well just save the expense and delicate glass tubes and use a resistor element instead. Coming down the range at night you'll still get some glow happening anyway (think hotplate element)!

Speaking technically (which is what this forum is for), heat is the random motion of particles of matter (e.g. molecules, atoms electrons). What you mean is that the lamp converts only a small proportion of the energy to visible light. Infrared is no more "heat" than is visible light. All is electromagnetic radiation, and all can be called "thermal radiation" in this case because produced by a thermal process.

With the lamp, only a small proportion of the energy needs to be removed by conduction and convection. Notice that a 50 W halogen is smaller than a 5 watt ceramic resistor. Radiation power is proportional to the 4th power of the thermodynamic (i.e. "absolute") temperature. We have maybe 400 K for a ceramic resistor versus over 3000 K for an incandescent lamp filament.

What matters here is not what stimulates the human eye, but what is reflected by polished aluminium and transmitted by polycarbonate.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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Post by acmotor »

I'm not certain which is more relevant to Ev's. The Faulty Towers (as I recall it) skit or the physics lecture on heat lamps.   Image

It is warming to see that the light shines at visible wavelengths when the topic dangles near weber's fav. topic. Image

BTW, professor, is there a wavelength of electromagnetic radiation that is not reflected by polished aluminium ? I've never given it much thought. (along with lots of other things Image )
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Post by coulomb »

Johny wrote: Hah - technical error. Basic is the character from Fawlty Towers NOT Monty Python

Bzzzzt: majot brain short circuit there. Sorry!   Image

Of course, I could be nasty and point out that the character's name is Basil Fawlty, as in "Basil's in the ratatoutille!".

But that would be needlessly vindictive, something we don't do here   Image
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Damn keyboard - thump, thump!

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Bugger the cream is overdone..
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Post by Goombi »

ACmotor   what is the best motor speed for AC Motor 2980rpm? for EV?

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Post by woody »

Goombi wrote: ACmotor   what is the best motor speed for AC Motor 2980rpm? for EV?
I know I'm not acmotor, but I'm going to answer anyway :-)

Short answer - assuming barina/swift/charade:

with an EV, you want a controller capable of 3-5 times the nominal motor power. E.g. 15kW motor -> 45-75kW peak controller.

with a gearbox, you probably want a 15kW nominal 2 pole motor (~2700-3600rpm nominal) with winding voltage 1/2 to 2/3 of your controller max voltage. (e.g. Weber + Coulomb's MX-5)

direct drive, probably 11kW nominal 4 pole motor (~1300-1800rpm) with nominal voltage 1/2 to 2/3 of your controller max voltage. (e.g. a4x4kiwi, red suzi except their motor voltage is approx equal to max controller voltage)

Really short answer:
It depends on what your goals are.

Long answer:
ac motors have an even number of poles, usually 2 or 4.
Industrial motors generally have a nameplate which will list the nominal RPM, Torque, Voltage for a given frequency.
In Australia the frequency is 50Hz, so the nominal RPM is just under 3000rpm for 2 pole motors, and just under 1500rpm for 4 pole motors. The reason the rpm is under is that the induction motor works by the squirrel cage rotating slower than the stator magnetism, which induces a current and opposing magnetism which gives the torque.
In other places the frequency is 60Hz, so 3600rpm for 2 pole, 1800 rpm for 4 pole.

In australia the normal 3 phase voltage is 400-415 volts, so an australian motor normally can be connected at that voltage.

Driving an electric motor (AC or DC) has an optimum ratio of V/Hz which for australian supply is usually 400/50 = 8 V/Hz. (VF Ratio).

Using an AC controller (Variable Frequency Drive / VFD) gives the motor a frequency to match its speed, at any voltage up to the VFD maximum voltage, so the motor can deliver maximum torque up to the speed that you run out of volts, i.e. a 415V/50Hz motor with a 415V VFD will only give maximum torque up to 50Hz which is ~1400rpm (4 pole) or ~2800rpm (2 pole).

It is also possible to order or rewind a motor for a lower voltage, e.g. 240V. This means that your VF ratio is lower (4.8), so you can maintain torque up to a higher frequency (87Hz) with a 415V controller, which gives you higher torque + power from the same motor. You need to deliver a correspondingly higher current however. The RPM would be ~2400rpm (4 pole) ~4800rpm (2 pole).

AC motors like DC motors are conservatively rated, usually can do about 3 times their rated torque for a few minutes, so a 15kW can do about 45kW. Using a 240V 15kW motor with a 55kW 415V controller, say 75kW peak.

cheers,
Woody
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Post by Tritium_James »

Goombi wrote: ACmotor   what is the best motor speed for AC Motor 2980rpm? for EV?
I'm not acmotor either, but I'm going to have a go too!

The best motor speed is up to the maximum that your gearbox can take, because this will provide the best power density out of the motor. Power = torque * speed. Motor size/weight/cost is about proportional to torque. So if you spin it faster, you can get more power for your size/weight/cost.

So the sweet spot is about 6-7000 rpm, because this is what automotive gearboxes and drivelines are designed to take. Lower, and you aren't using the full available range. Higher, and you need a specialised gearbox like we have in the Porsche.

As an example of what pushing things gets you, that setup is getting 150kW out of a motor that weighs ~50kg and is 250mm diameter / 350mm long. The downside is it's running up to 12000rpm, and you can't do that with a normal gearbox - well, not for long, anyway.

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Post by Goombi »

James I cannot possibly entertain my manufacturer with 6-7k speed motors. Wheather is sweet or sour. But i understand your drive-- here i go again please gentleman try a little ecconomy sensible speeds and longer drives.I am more inclined to follow Woodies message.. Its possible --gentle enough and performance acceptable and ecconomicaly viable..It makes sense Good one woody-- Thank you both for your input

If i am going to bring in AC Systems on the market i will need precisely very correct information to make the system work well and sucesfully.The whole baboodle should be close to 3000 USD and that will be a great improvement on current AC systems   and can get the motors converted to any configuration. All i need is a correct guideline and information.
Cheers
Last edited by Goombi on Wed, 22 Jul 2009, 13:05, edited 1 time in total.

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Post by acmotor »

Hi I am acmotor. Image

This is a bit off topic but here goes...
TJ's comment on power density is good. It targets a performance market.
Woody's is good. It targets a functional market and points out the voltage range issue. I agree with all that was said, I think. (these guys know more than me anyway, I just play with EVs ! Image )


Me ? I would like to see no more than twice the nominal revs of a 4 pole motor used for 60kmph (so 3000RPM) cruise.

I am convinced that a 2 pole motor is not good power to weight in any circumstance.

Lower voltage, at least 4 pole and increased frequency produce the better power to weight by far.
If the ACpropulsions motor was 8pole and twice the frequency and half the voltage then it would be the same size (it is 4 pole now isn't it TJ ? ). Then it would have 6000RPM max revs and be so so so much more useable. Particularly as a direct drop in for an ICE or direct drive to a shorter diff.

Goombi, I for one don't have a neat solution for AC if the target is below US$3000. One day !
BTW, I don't think market works that way. There will always be people who will buy the best offering, and people who will buy the cheapest offering. Image

You ask for the correct guideline. Sorry, I don't have one. Only suggestions. I firmly believe in losing the (changeable)gearbox and clutch. Image

That probably didn't help a single bit. Oh well. Image
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edit: d'oh hit post button too early. See the next one!
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Post by woody »

Goombi, if you can get an ac motor/ controller combo which is about 15kW continuous and 50kW peak and peak is at about 4500 rpm, you'll have a great "goombi style" kit to suit most vehicles.

I'm torn between acmotor's "chuck the gearbox for efficiency" and weber/coulomb keeping it for performance and fun.    
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Post by Tritium_James »

The power density argument also affects price. More power dense = less materials = lower price (in higher volumes).

If the ACP motor was modified to they spec you say, that would be fantastic. About the same size, half the speed, twice the torque, and useable with conventional automotive parts at 6000rpm. But then it would be running at 800Hz. I can't see it being too efficient at that operating point.

acmotor, your 'ideal' motor I agree with entirely. 4 pole, 3000rpm at 60 (maybe 65) km/h. This is only double the 'normal' frequency, so losses shouldn't be too bad. Then for highway use you push it to 6000rpm, which gets you to 120 (maybe 130) km/h. So it's running at 200Hz at this point. Efficiency drops a bit, but it's a simple elegant system.

So Goombi, if you're sourcing cheap AC motors, you'd want one with 4 poles, 1/4 the normal voltage, and thinner laminations than usual, to support operating without too much loss out to a nominal 100Hz, with a maximum of 200Hz. It would also need to be balanced for 6000rpm. The power rating would be up to you, it's going to depend on all the usual things - size/weight of the car, desired performance, if you're keeping changeable gears, etc, etc.

That's my 2c, anyway!

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Post by acmotor »

I understand the thinking TJ, but AC150 runs at 400Hz now. Even if it lost a bit more at 800Hz it would not equal the loss of a gearbox ?

My experiment with 200Hz on a 50Hz motor showed that the overall efficiency remained essentially the same on a garden variety motor. The AC150 is just a garden variety 400Hz motor ( Image ).
Actual loss watts increased... yes an issue with heat possibly. But not everyone would use a 150kW motor at 150kW for long anyway.
How long do you hold your ICE at 6000 RPM ?

My impression was that the 400Hz was a sign of the times i.e. what was reasonable as a controller 15 years ago when the AC150 was first built ? After all 400Hz motors have been around for zonks. There are even specific web sites.... http://www.400hertz.net/company.htm

Only toying with thoughts here.
I guess Goombi's question on revs is a bit of a key to the success of a motor ?
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Post by Goombi »

Thank you all i am glad i got you interested in a line of thought to best design a roadmap for a standard AC Motor and controller support.
I have not heard of performance details --what speed at pick up at start up-- how fast to 3000rpm =60km/h speed (seconds?)
How can a 15 kw ac go to 95Km/h with gearbox support5th (gear) at no more then 2500-2700rpm.
What battery voltage will one need to use --(120volt) 800amp total--
And an estimate how far will this ACEV travel.
We also have the 2 pole and 4 pole preference.
Yhere is a need to decide which is the best performing combination and which is just a little better- faster More --(ELEGANT) then DC Image System
If we could agree on a patern within a reasonable 3000rpm range
weather its 2 pole -4 pole 10 Kw or 15 kw motor and what ever Hz will be required then i can see a picture for providing acessible AC power plant. in regard of someone buying the most expensive and best it's not always the case. As soon as i have some kind of a image of what is needed i will provide you with pictures and details,
In AC case only the motor and controller will be offered.
As far as i know chinese controllers makers they always do a complete job with full wiring-- but i doubt they will provide WATERCOOLING.
Not forgetting to produce a sensible powerplant without overheating moving up to 95 km/h and NOT going measly 20 km in distance. 50+KM is my meanest estimate.
So far this can be achieved with current 2800rpm dc series power
So we have to use a AC system as upgrade and betterment not for its ELEGANT looks but to introduce -more efficient less complicated plant.
Basically we need a standatd one or 2 prototypes One good for small to medium vehiclen and one for performance
Please make your individual submissins every idea is valuable
Back tomorrow Cheers



Image Image
Last edited by Goombi on Wed, 22 Jul 2009, 20:50, edited 1 time in total.

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Post by coulomb »

Goombi wrote: How can a 15 kw ac go to 95Km/h with gearbox support5th (gear) at no more then 2500-2700rpm.
It probably can't - not continuously, if it's a controller-motor package. Because then 15 kW continuous really means 15 kW continuous. When we talk of an industrial motor at 15 kW, we overvoltage it, and it becomes at least 20 kW continuous, possibly more.

If you are thinking of low voltage (120 VDC), then overvoltaging seems unlikely - but at any rate you leave those details to the manufacturers. So for a Charade/Barina at 95 km/h, 15 kW continuous is a bit low, probably 18 kW is the minimum.

For reasonable puckup, you would want at least some 30 kW peak (others may have more precise ideas; I've only considered performance vehicles so far).
What battery voltage will one need to use --(120volt) 800amp total--
My understanding is that a lot of the Chinese manufacturers are going to 320 VDC to 360 VDC. This isn't necessarily more expensive - you just need more batteries/cells in series, and they can be smaller Ah.
And an estimate how far will this ACEV travel.
Perhaps 15% further than the same DC vehicle would travel. Say 10% more for the regen (5% more than a DC with regen), and 5% for efficiency. Of course, it depends hugely on the batteries: what type, how many, and how much drain they see.
We also have the 2 pole and 4 pole preference.
I would say leave that to the manufacturer - but specify that you want low revving (if you do - I see no problem with 6000 rpm as long as it is designed for it (well balanced). It's not like it will be screaming like a petrol engine).

For a higher performance option, I'd say at least 20 kW continuous, and at least 50 kw, preferrably 60 kW peak. This isn't race car performance, this is just a bit better than the engine it replaces. For real race car performance, you need at least 80 kW preferrably 100 kW peak.
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Post by Goombi »

Thanks for comprehensive answer"coulomb"
A sugestion of 18 Kw ac motor = 24-rated HP --- 1.3 cc Barina is rated at 28hp and developing 74 Brake hp at 6500 rpm. Re speed   If you run Barina at 100 Km the ICE motor has to move at 3200 RPM Top gear..
The comparison with ACEV a ac motor will be comfortable at 2800rpm to reach 92 km/h This top speed is absolutely satisfactory for general commuter vehicle. This discussion is purely about basic 3000 rpm motor 11-15 kw AC. My original barina had 8.5 Kw - 11.5 hp at 2200rpm @ 200 amp only reaching 74 km/h with new Series speed motor of 2800 same barina will reach 95 km/h with 400 amp input. and jump the starting barrier at 30 % faster.( without regen)
Lets memorise these figures and see if we can improve on it with AC systems.
If we start from a low base with AC we will reach satisfactory result.
With the help of My maufacturer and support from theit tech staff i should be in position to present some kind of formulae for next generation AC systems. I noticed that there are 2 CAMPS in AC Forum-- one for high performance (Hooning) and the other for general run of the mill.
Why did some chinese car manufactureres switched to AC ?
Complete motors controllers and accessories are available off the shelf for 72 volt 4.5 Kw ac system.That is what is in the papermache chinese cars. top speed 45 km/h and 100 km distance (questionable)These supercharged wheelboroughs are running on the latest technology in AC The manufacturer is mine and i fail to see why they will not go for higher capacity motors and AC controllers. I am sure they already have them.---------------------------------------
AC Asynchronous Motor Driving System
AC Asynchronous Motor Driving System is made up of AC Motor and the corresponding Controller. Compared with the DC System, it has the advantages: Brushless,Maintains-free,high-efficient,big power density,Wide range of speed regulation,Large torque,Electromagnetic Brake,Regen Electricity,strong overload capacity, Stepless Speed Change。Because of the advantages, it has replaced the DC System.
Feature :
DSP Total digital control                  IGBT Watt Module
Space vector control                      Stepless Speed Change
Energy feedback and electric regen brake     Motor Parameter recognized automatically
Programmable with hand-hold Unit        RS485or CAN Main line correspondence
Auto-adapted air blower control
Protection Function:
Battery under and over volt Protection          Dual over current protection
Limited Speed Protection                    Power Limited on High Speed

If anyone like to see what is available in AC motors from 1-100KW
please send me your e-mail to--- conversion@dodo.com.au
The tables that they are written on do not fit correctly in this window.
Coffee Cheers
Last edited by Goombi on Thu, 23 Jul 2009, 06:45, edited 1 time in total.

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Post by woody »

Goombi wrote: Thanks for comprehensive answer"coulomb"
A sugestion of 18 Kw ac motor = 24-rated HP --- 1.3 cc Barina is rated at 28hp and developing 74 Brake hp at 6500 rpm.
Not quite following you here.
1.3 L = 1300cc.
Rated at 28hp ? (Is this the old british taxable horse power?)
74 bhp @ 6500rpm <- that makes more sense
Goombi wrote:Re speed   If you run Barina at 100 Km the ICE motor has to move at 3200 RPM Top gear..
The comparison with ACEV a ac motor will be comfortable at 2800rpm to reach 92 km/h
The nominal AC speed is just nominal, i.e. the controller should be able to spin the motor much faster than that, at inversely reduced power. i.e. if peak power is at 2800rpm, say 30kw, at 1.5 times the speed (4200rpm) the power is still 1/1.5 = 20kW. At double (5600rpm) the power is half (15kW).
Goombi wrote: This top speed is absolutely satisfactory for general commuter vehicle.
Agreed 92 is enough, but it will go faster.
Goombi wrote: This discussion is purely about basic 3000 rpm motor 11-15 kw AC. My original barina had 8.5 Kw - 11.5 hp at 2200rpm @ 200 amp only reaching 74 km/h with new Series speed motor of 2800 same barina will reach 95 km/h with 400 amp input. and jump the starting barrier at 30 % faster.( without regen)
Lets memorise these figures and see if we can improve on it with AC systems.
If we start from a low base with AC we will reach satisfactory result.
With the help of My maufacturer and support from theit tech staff i should be in position to present some kind of formulae for next generation AC systems. I noticed that there are 2 CAMPS in AC Forum-- one for high performance (Hooning) and the other for general run of the mill.
There's just one campground. Some people put their tents at the end next to the dragstrip and the mountains, some people put their tents at the end next to the golf course and the retirement village, some people are in the middle :-)
Goombi wrote:Why did some chinese car manufactureres switched to AC ?
Regen?
Goombi wrote: Complete motors controllers and accessories are available off the shelf for 72 volt 4.5 Kw ac system.That is what is in the papermache chinese cars. top speed 45 km/h and 100 km distance (questionable)These supercharged wheelboroughs are running on the latest technology in AC The manufacturer is mine and i fail to see why they will not go for higher capacity motors and AC controllers. I am sure they already have them.---------------------------------------
AC Asynchronous Motor Driving System
AC Asynchronous Motor Driving System is made up of AC Motor and the corresponding Controller. Compared with the DC System, it has the advantages: Brushless,Maintains-free,high-efficient,big power density,Wide range of speed regulation,Large torque,Electromagnetic Brake,Regen Electricity,strong overload capacity, Stepless Speed Change。Because of the advantages, it has replaced the DC System.
Feature :
DSP Total digital control                  IGBT Watt Module
Space vector control                      Stepless Speed Change
Energy feedback and electric regen brake     Motor Parameter recognized automatically
Programmable with hand-hold Unit        RS485or CAN Main line correspondence
Auto-adapted air blower control
Protection Function:
Battery under and over volt Protection          Dual over current protection
Limited Speed Protection                    Power Limited on High Speed

If anyone like to see what is available in AC motors from 1-100KW
please send me your e-mail to--- conversion@dodo.com.au
The tables that they are written on do not fit correctly in this window.
Coffee Cheers
All those buzzwords look OK to me :-)
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Soapbox on regenerative braking

Post by Johny »

woody wrote:The nominal AC speed is just nominal, i.e. the controller should be able to spin the motor much faster than that, at inversely reduced power. i.e. if peak power is at 2800rpm, say 30kw, at 1.5 times the speed (4200rpm) the power is still 1/1.5 = 20kW. At double (5600rpm) the power is half (15kW).)
Ouch!Image

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