Richo's AC Handi Sports

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Richo
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Post by Richo »

Yeah sorry I put the plot in first then the text - you're too quick Image

I did the dyno run today.
Was a pretty good laugh.
I was half expecting it to blow and take it home on a tow truck.
So the short answer is NO but the long answer is YES.
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Post by woody »

Real world numbers! :-)
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack
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Post by Richo »

Still hunting for that elusive flywheel and clutch assembly.
The wrecker has them but they are still in the car and it's not worth the time to pull a motor out just to sell the flywheel/clutch assembly.
My next option is to buy a Sirion wreck and strip it down myself.

In the meantime I pulled out all the false floor panels from the back.
These came to 11kg.
The spare tyre, jack and tyre iron came to 8kg but I'll put these back in.
There was also about 1kg of sand courtesy of the previous owner.
I also found a buck for my cleaning efforts Image

I had a type 1 child restraint mounting point installed as the car had none.
As it is a 2 seater I can legally have a child seat in the front.

I have noticed that the fuel tank under the car only goes 2/3 to allow room for the exhaust system.
Once I strip the car down I'll have a better look to see if I can make a full width battery box to replace the fuel tank.
This will keep the centre of gravity low and central.
So the short answer is NO but the long answer is YES.
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Post by AMPrentice »

what will be the weight without ice gear?
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Post by Richo »

Not too sure at this stage.
Once I rip all the ICE parts out I will remeasure the weight.
I'm still optamistic that I'll keep the weight the same or slightly lower after conversion.
So the short answer is NO but the long answer is YES.
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Post by AMPrentice »

I remember my 83 suzuki hatch was rated at 560kg while ice gear was about 100kg or 460kg as a "glider". Didnt have the aero of the Handi but all these "Kei" cars are so small they are great candidates for EV converts.
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Post by Richo »

The earlier cars do tend to be a bit lighter.
Even the earlier Handi (Handivan/Mira) was lighter - but it doesn't have the same newer features such as airbags or even a glove box etc.

Anything that is small and light makes a good conversion as long as you aren't expecting a long range due to the limited battery spaces.
Which is why I chose the handi which has a lot of extra space for it's size.
So the short answer is NO but the long answer is YES.
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Post by T2 »

Hi Richo, I see that no know-it-all has bothered to stop by and stick his nose in your business and help you design your powertrain, so since it appears that you are in such obvious need of direction I'll be that person and we'll make this a kick a$$ project. No, you don't have to thank me. But you can get off your knees now and stand back while I approach this thing and take a real strong whiff of what we have here.

Your 415v delta 4kw motor probably draws around 8 amps. Eight amps ! Well it goes almost without saying , that that Katie Perry dreamworld will soon be ended when I have my way. In my hands that pathetic excuse for an electrical machine is going to be raised to 8Kw continuous with a possible abusive peak towards 24Kw. That said, it would be remiss of me not to mention that it could have been higher had not you, Richo, in your wisdom, decided to go ahead and choose 4.5 : 1 gearing but 4.5 is better than nothing I suppose. You were obviously not aware of my penchant for the 10 : 1. Go ahead, since you are determined to do bad physics, don't let me stop you. I hate to use stern words but I am afraid we just lost the opportunity there to go double on the power. Never mind. To continue.

Amongst other things like a motor rewind, we will be needing a battery pack of 130Ahr cells able to supply 300 amps while maintaining a terminal voltaqe of 104 Vdc first off. This will enable the inverter to provide the motor, when reaching full power, a maximum AC voltage equivalent to 77 Vac 3ph in the form of a modified sine waveform. (Neutral Wobble)
(Coulomb assures me, in fact he stakes his reputation on it, or to be more accurate I'm the one staking his reputation on it, that a 312Vdc bus voltage can produce 232 Vac.) I, in turn, merely divided these figures by three to give both a suitable low voltage bus and the AC voltage it can supply.

That these numbers are not scientific nor cast in stone, may allow you to breathe a sigh of relief, but having said that it is imperative that the motor winding should be tailored to suit the electrical and mechanical situation wherever possible. With a single ratio gear reducer this choice is even more crucial since only the battery voltage allows flexibility at this point. It may further sadden you to know that the amps and the volts will not make an iota of difference to your car's initial acceleration performance. That was already decided way back when you chose that motor with that differential gear ratio.

In the aftermath of that decision I just want to cut down on the number of connections and the cost of the BMS for you. Perhaps you have already noticed that the cost of the BMS will be proportional to the number of cells and not their ampacity. Put like that it's a no brainer to have fewer cells. I'll agree for you in advance on that one.

At 3000 RPM the vehicle will be at 75 km/hr and we need to be specifying full power to be reached by then and not before. This is the most important defining statement I can make and cannot be challenged. The road speed of 75km/hr sets the motor base speed at 3000 rpm. It is therefore important that both the battery voltage and the eventual motor V/Hz, following the motor rewind, must unite for this figure.

In which case we are going to need a motor of V/Hz = 77Vac/100Hz ~ 0.77 V/Hz

The '100' because a 2 pole-pair per phase motor requires 100Hz to rotate at 3000rpm.

Currently the target motor is wound for 415Vac @ 50Hz where V/Hz = 415/50 ~ 8.0 V/Hz

A rewind order therefore requires replacing the stator turns on a ten for one basis. This wire should be capable of 80 amps to maintain the continuous torque level as before and the wire gauge should be chosen to ensure a 100% slot fill. With the rotor removed it may be opportune to also have a rotor balance performed at this time. Since even the expected maximum of 4500 rpm is a fairly low speed I would recommend leaving the integral fan in place unless fan roar or balancing is found problematic.

Continuous power should be correspondingly 77Vac/41.5Vac x 4kw = 7.4Kw nominal.

Peak current should now be able to approach 250 Amps.   
Peak power with 250 Amps should show a corresponding increase to 23Kw.

What is not being said here is the following :

There is no way the nominal torque of a motor can be changed purely by changing the wiring with a rewinding process. The most you can do is lower the back emf by reducing the number of turns in order to facilitate the stator current flowing in the stator slots to not be curtailed by the effect of the lack of voltage headroom in conjunction with rising frequency. This ensures that the constant torque prevails.

The motor's nominal torque will demand a certain nominal current. There is therefore a constant copper loss in the stator winding for this. This loss applies whether the rotor is spinning at 10rpm or 10,000rpm. Clearly it is advantageous to set gearing conditions that would permit the motor to spin as fast as possible and provide more power in order that the impact of this loss is diminished. In the face of this loss and if it were the only loss the motor efficiency would indeed improve the faster the motor spins.

Power ratings for a particular frame size have no meaning when an inverter enters the picture since copper loss is constant and iron loss increases exponentially to the power of 0.7 above nameplate rating such that a fourfold increase in speed comes with a continuous power increase of 4^0.7 ~ 2.6. In this specific design the improvement gained by doubling the nameplate 1500 rpm to 3000 rpm is 2^0.7 ~ 1.625 The increased cooling from the fan will actually lower the case temperature so the real life performance may be as much as 3 times the nameplate for a safe continuous power rating.

Continuous power in an automotive setting has no real meaning either unless in a racing situation. A 16Kwhr battery pack is in no way to be considered continuous power in the accepted sense. It is merely, for the most part, a one hour rating. Industrial motors OTOH are rated 24/7 in a 40 deg C ambient with an 80 deg C rise. This is an extreme condition never seen by an EV parked outside in the road in most countries. Furthermore traction motors are often bolted to adapter plates acting as heat spreaders and other items of high thermal mass which are not significant heat generators. Traction motors are located underneath the vehicle and shielded from radiation from the sun or any other heat source, unlike similar motors in an industrial setting.

With spirited driving peaking at 24Kw will this motor eventually run hot as the battery nears depletion ? Yes I certainly hope so, in fact I am positively banking on it. Will this motor burn out ? Well first you have to ask yourself, have you ever read about someone else ever roasting an AC induction motor ? And the answer to that is not in the infirmary. Nor in the affirmative either ! Of course normal precautions like having 38 psi in the tyres, synthetic oil in the transmission and a partially blocked radiator grille can help.

Earlier on I mentioned that volts and amps won't contribute an iota of difference to your car's initial acceleration performance. That is mainly true but drivability in the upper speed ranges is severely affected unless the winding V/Hz. is correct. Having it set too low can always be fixed by a controller of greater ampacity. Having it set too high on the other hand will require the arduous and time consuming task of accommodating more cells to move the base speed and hence the power peak further along the road speed axis.

I don't know what it's like to live in Australia, Richo, but here in Canada we have a lot more cars on the road than we used to. Cutting you off and generally getting in your way and causing you to be late for appointments and causing all sorts of nuisance. And you may have probably also noticed, as have I, that these cars are mostly driven by the wrong sort of people as well. Consequently I feel it is incumbent on us in the EV community not to be putting out there, vehicles with poor drivability. So I hope that some of what I have written can be useful to you in this regard.

Physics as if people mattered.
Last edited by T2 on Thu, 05 Jul 2012, 07:46, edited 1 time in total.
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Post by bga »

Ha! very entertaining, T2

I have always thought that Canadian drivers are very polite compared to Western Australian drivers Image
As a thought; it's the winter that sorts out the real dills with all those snow drifts and slippery ice, not to mention Mooses.
(Being from Ontario myself, I like Mooses; However, in Aus. we have Kangaroos that mostly wreck the front of the car and don't end up inside on your lap Image)

My new theory:
You know all the rice racers with really big tachos above the dash or stuck to the 'A' pillar? They are really clocks with the words "you're late!" flashing on the face.

Perhaps it's an age thing, but I've given up looking at the clock when in the car. I'll get there when I get there and, if I'm late, I should have started out earlier. Much better for avoiding tailgating and vast numbers of lane changes.
It's not the end of the world, but I can see it from here.
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Post by Richo »

If you get board easy I suggest skipping ahead and look at some pretty pictures.
T2 wrote: Hi Richo, I see that no know-it-all has bothered to stop by and stick his nose in your business and help you design your powertrain
Yay - Everyone is entitled to share their opinions and thoughts
T2 wrote: Your 415v delta 4kw motor probably draws around 8 amps... In my hands that pathetic excuse for an electrical machine is going to be raised to 8Kw continuous with a possible abusive peak towards 24Kw.
Close the motor draws 8.8A in it's natural boring state - A gold star for you anyway.
And in its stock form already has a peak of 19kW - Which is why I have it.
So your 24kW is not impressing me much so far.
T2 wrote: in your wisdom (you) decided to go ahead and choose 4.5 : 1 gearing but 4.5 is better than nothing I suppose. You were obviously not aware of my penchant for the 10 : 1.
4.5:1 is just the differential ratio.
The gearbox still has the usual 5 changeable gears.
So in first I would have the usual 14.3:1.
I chose this as this is the cheapest/easiest method of getting the power to the wheels.
At this stage there is no reason to pay extra to get a fixed ratio of 10:1
Perhaps later when I vaporise or snap something.
T2 wrote: Amongst other things like a motor rewind, we will be needing a battery pack of 130Ahr cells able to supply 300 amps while maintaining a terminal voltage of 104 Vdc first off. This will enable the inverter to provide the motor, when reaching full power, a maximum AC voltage equivalent to 77 Vac 3ph in the form of a modified sine waveform.
See here is where you lost me.
You say the inverter can only handle 104Vdc.
Please whatever inverter you may have I don't want as it sounds like a toy for a golf cart.
I have optimised my conversion for 400Vac. That is Not a typo - 400Vac
Now for your batteries 104V@300A is 31kW.
Remember this is a car and not a golf cart.
I will be using 2 strings of 220 LiFePO4 in series at 10Ah ea for a total of 440 cells(14kWh).
This is a nominal of 704Vdc. Fallen off your chair yet...
Under full load I expect a draw of 180Adc(9C) with a terminal voltage of 567Vdc(400Vac - without wobble re efficiency v harmonics)
Or in layman's terms a shade over 100kW.
T2 wrote: With a single ratio gear reducer this choice is even more crucial since only the battery voltage allows flexibility at this point.
GEARBOX dude GEARBOX
It came free with the car.
T2 wrote: It may further sadden you to know that the amps and the volts will not make an iota of difference to your car's initial acceleration performance. That was already decided way back when you chose that motor with that differential gear ratio.
Well that is what I expected but I'm not really saddened by it.
Given the original petrol motor when new has a peak of 88Nm and the electric motor I have chosen has a peak of 120Nm I feel I am justified that it was the right decision.
And an initial ratio of 14.3:1 seemed fair to me.
T2 wrote: In the aftermath of that decision I just want to cut down on the number of connections and the cost of the BMS for you. Perhaps you have already noticed that the cost of the BMS will be proportional to the number of cells and not their ampacity. Put like that it's a no brainer to have fewer cells. I'll agree for you in advance on that one.
I do agree less wiring is preferred.
And yes the cost of the BMS will be proportional to the number of cells.
But it is up to the designer of a BMS to cut down the costs by the way it is engineered not by restricting the number of cells I should have.
T2 wrote: It is therefore important that both the battery voltage and the eventual motor V/Hz, following the motor rewind, must unite for this figure.
In which case we are going to need a motor of V/Hz = 77Vac/100Hz ~ 0.77 V/Hz
All of which is totally irrelevant since it is based on some controller you don't describe and is obviously not up to the task of my conversion anyway.
T2 wrote: A rewind order therefore requires replacing the stator turns on a ten for one basis. This wire should be capable of 80 amps to maintain the continuous torque level as before and the wire gauge should be chosen to ensure a 100% slot fill.
Well sorry I just go to the rewinder pay some money and it becomes their problem what wire they shove in it. F*&ked if I'm going to sit down and solve their problem when I'm the one paying. It's what I did before and is what I will keep doing.
T2 wrote: With the rotor removed it may be opportune to also have a rotor balance performed at this time.
The one I have is ok for 6,000RPM but what they hey I'll tell'em I want it to go to 10,000RPM just 'cos you suggest...
T2 wrote: Since even the expected maximum of 4500 rpm is a fairly low speed I would recommend leaving the integral fan in place unless fan roar or balancing is found problematic.
Nah it's coming off.
1. The electric fans are more efficient. Even thermo fans for an ICE were common in the 80's
2. While I'm driving down the road the air forced through the front grill is more air than that poxy fan will ever do.
3. City driving has a low service factor - Red means stop Green means go...
T2 wrote: Continuous power should be correspondingly 77Vac/41.5Vac x 4kw = 7.4Kw nominal.
Peak power with 250 Amps should show a corresponding increase to 23Kw.
And my target numbers are 14kW nominal and 70kW peak.
But I find the car quite good for my daily drive so anything over 40kW is acceptable to me as this is what it currently has.
T2 wrote: There is no way the nominal torque of a motor can be changed purely by changing the wiring with a rewinding process.
True ok I'll make sure it stays the same.
T2 wrote: Continuous power in an automotive setting has no real meaning either unless in a racing situation.
Only because no one would by a V8 with 30kW continuous power over the same V8 with 250kW peak.
As some people have found out their souped-up turboed cars overheat in summer driving around in congested city traffic.
They only measure peak on the dyno not continuous.
If only they knew...
T2 wrote: Industrial motors OTOH are rated 24/7 in a 40 deg C ambient with an 80 deg C rise. This is an extreme condition never seen by an EV parked outside in the road in most countries.
Except (since this is the AUSTRALIAN electric vehicle association) in Australia where 45DegC is NOT uncommon and easily over 50DegC in confined areas in the sun such as cars parked outside. Actually last summer was a record breaker. So the usual spec'd rewind is an issue.
T2 wrote: Furthermore traction motors are often bolted to adapter plates acting as heat spreaders and other items of high thermal mass which are not significant heat generators.
Mmmm it's called a gearbox.
T2 wrote: With spirited driving peaking at 24Kw will this motor eventually run hot as the battery nears depletion ? Yes I certainly hope so, in fact I am positively banking on it.
Gotcha - don't touch the motor after "hooning".
Good advice.
T2 wrote: Having it (V/F) set too high on the other hand will require the arduous and time consuming task of accommodating more cells to move the base speed and hence the power peak further along the road speed axis.
With an ostentatious 500kg of optional cell placement room in this automobile base speed and hence peak power are not an issue for increased adjustment along the road speed axis. Image
T2 wrote: I don't know what it's like to live in Australia, Richo, but here in Canada we have a lot more cars on the road than we used to.
I have found both to be about the same. But as BGA has pointed out we have less snow so have more consistent road conditions.
T2 wrote: I feel it is incumbent on us in the EV community not to be putting out there, vehicles with poor drivability. So I hope that some of what I have written can be useful to you in this regard.
So the moral is of your story is not to build anything like you suggest.
Agreed.

So in summary:
Car 690kg
Battery 704Vdc/100kW@9C/14kWh
Controller 100kVA
Motor 14kW cont / 70kW peak

DRIVEABLE
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!
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Post by Richo »

And now for the pretty pictures Image

Image
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!
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Post by Nevilleh »

Luvverly pictures! Looks like 4th gear is the way to go. Don't know if I'd like to be driving the thing at that indicated 160+ kph though.

T2's missive was interesting and amusing. I think I got the idea that he was thinking of an inverter driving the motor controller, or a motor controller with such an inverter designed in to the front end. That would allow a lower battery voltage and still enable the high peak voltage needed for an industrial 3-phase motor to be achieved. I wonder if anyone has made a controller with that feature?
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Post by T2 »

Hello again,

Richo, you didn't miss the tongue-in-cheekness of my post and take umbrage did you ? Next time, play along, and express outrage but seek the high road, you'll come out looking the better for it, believe me.

Close. the motor draws 8.8A in it's natural boring state - A gold star for you anyway.
And in its stock form already has a peak of 19kW - Which is why I have it.
So your 24kW is not impressing me much so far.


How did you know 19Kw peak ? You said you could hardly make out the nameplate label. Also I can't ever remember seeing peak power on any motor nameplate come to think of it.

You now say that the full multi-ratio gearbox is present, my mistake, with the clutch missing I assumed the internals of the gearbox had gone too and you were going the so called 'direct drive' route.

With a 4.5 : 1 ratio going "direct" would have avoided approximately a 15% torque loss traversing a multi-ratio gear box but remains viable if you can run 3.5 times nominal rated current while accelerating.

On the other hand the retention of the gearbox adds advantages in peak power and thence drivability however much of my previous post remains relevant even for this situation. In which case selection of second gear could give you an overall 9 : 1 which is much closer to optimal.

Besides that you seem to be coming out with numbers not released in earlier posts and then hitting me over the head with them. to continue, I wrote :

"Amongst other things like a motor rewind, we will be needing a battery pack able to supply 300 amps while maintaining a terminal voltage of 104 Vdc first off. This will enable the inverter to provide the motor, when reaching full power, a maximum AC voltage equivalent to 77 Vac 3ph in the form of a modified sine waveform."

See here is where you lost me.

How so ? We agreed fewer cells are better, then as far as lower voltage controllers go, Curtis is the leader in this area, I thought you might know that. I wanted to maintain credibility by avoiding a gratuitous mention of a commercial product but the Curtis 1238R -7601 (equipped with a liquid cooled cold plate) capable of 650Amps at 108Vdc was the choice of drive I had in mind. In this case the battery limit and motor limit would be both set to 250 Amps which gives plenty of room for improvement later on.

For a supply this time around I would use two strings of cells but of the same 40Ahr CALB cells used in the car of Weber and Coulomb. Their BMS design would be cost competitive and have good local support being here in Australia. The 250 Amps would require a maximum of only a 3C rate and enhanced reliability in an 8Kwhr pack. Plus I promised 24Kw peak from your motor so a 250Amp draw is in agreement with that.

You say the inverter can only handle 104Vdc.
Please whatever inverter you may have I don't want as it sounds like a toy for a golf cart.


No toy. 104 volts DC can still kill you. That's if you care enough.

I have optimised my conversion for 400Vac. That is Not a typo - 400Vac

You've optimised nothing. You have simply taken a derelict motor and allowed it to wag your dog of a design. What you should be doing is organising a rewind so that you don't start getting a rapid torque decline following a premature power peak as I have been trying to explain.

Now for your batteries 104V@300A is 31kW.

Remember this is a car and not a golf cart.


But neither is it a Lexus, Sir Charles, may I remind you.

I will be using 2 strings of 220 LiFePO4 in series at 10Ah ea for a total of 440 cells(14kWh).
This is a nominal of 704Vdc. Fallen off your chair yet...


No, but I'll be fallen asleep soon....

But it is up to the designer of a BMS to cut down the costs by the way it is engineered not by restricting the number of cells I should have.

And there was I, thinking you didn't have a sense of humour.

And when I wrote :
"It is therefore important that both the battery voltage and the eventual motor V/Hz, following the motor rewind, must unite for this figure.
In which case we are going to need a motor of V/Hz = 77Vac/100Hz ~ 0.77 V/Hz"

All of which is totally irrelevant since it is based on some controller you don't describe and is obviously not up to the task of my conversion anyway.

Not true. Practically all controllers will deal with the cards they are handed in the same way. The V/Hz of the motor and the bus voltage are all they care about. They will of course stall out in current limit if the gear ratio is not favourable on a hill, but the more likely condition is to be unable to provide even rated power to the motor not long after the motor has hogged all the available output voltage at the low rpm part of its range.      


And my target numbers are 14kW nominal and 70kW peak.
But I find the car quite good for my daily drive so anything over 40kW is acceptable to me as this is what it currently has.

So in summary:
Car 690kg
Battery 704Vdc/100kW@9C/14kWh
Controller 100kVA
Motor 14kW cont / 70kW peak

DRIVEABLE


Perhaps I should leave now, in case I start to say some things that I shouldn't be saying.
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Post by coulomb »

T2 wrote: You've optimised nothing. You have simply taken a derelict motor and allowed it to wag your dog of a design. What you should be doing is organising a rewind ...

T2, I think you might have missed that even though Richo is providing 400 VAC, and his motor is currently designed for ~ 400 VAC, he is still doing a rewind:
Richo wrote: Well sorry I just go to the rewinder pay some money and it becomes their problem what wire they shove in it. ... It's what I did before and is what I will keep doing.
So it will still be doing what you suggested, just not as very low a V/Hz ratio as you suggest, since he has 5x the bus voltage of the Curtis controller. The Curtis 1238-7601 and even the soon to be released 144 V version are still a bit light on for peak power, at some 50 kW.
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Post by Richo »

Nevilleh wrote:Don't know if I'd like to be driving the thing at that indicated 160+ kph though.
Actually it's pretty stable at 110kph so it should be ok at 160.
The speedo only goes to 160kph anyway.
Feels like a challenge now to see if I can get it there
Nevilleh wrote: I think I got the idea that he was thinking ...a motor controller with such an inverter designed in to the front end. That would allow a lower battery voltage and still enable the high peak voltage needed for an industrial 3-phase motor to be achieved.

I did look into this.
It is possible - but it's not cheap. ~$40/kw ($4000 for 100kW)
So the short answer is NO but the long answer is YES.
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Post by Richo »

Curtis never made much of a reputation here in Australia.
Most people tend to avoid them if possible.
It maybe different over in Northen America.
If anything I would have gone for a stripped out industrial controller.

The motor rewind will happen after installation and testing around the local streets which are limited to 50kph.
The rewind will be ~110Vac@50Hz.
This gives ~3.6 times nominal RPM or peak at 5400RPM@180Hz@400Vac.
It's not critical in this case as I have a generous margin of acceptance of 40-70kW.

The only driveability problem I expect is wheel spinning in all gears.
Well some may say this is not much of a problem Image
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!
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Post by woody »

I think you've both got good
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack
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woody
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Richo's AC Handi Sports

Post by woody »

You've both got good ideas, but:
Different Goals => different answers

E.g. A high voltage lifepo4 pack with a BMS is probably not going to satisfy a goal of low complexity
Neither is building your own controller
Deciding on a donor car first (like me) is going to change some answers too

State your goals and it gives us all an insight into your reasoning, and something simpler to argue about :-)
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack
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Post by Nevilleh »

I don't know where you got that sort of price from, sound way too much to me.

Seems to me, I could build a boost converter to take say 150-odd volts input and step it up to 650V which is enough to power a variable frequency 3 -phase motor controller - which could be simplified as it doesn't/wouldn't need PWM for power control as I could vary the o/p volts of my boost converter. Such a converter would only need a switch, a choke, a capacitor (or two) and a diode, plus some control electronics, so I can't see the cost being all that high. Then the VFD for the motor, again simpler because it doesn't need PWM. Might be an interesting concept to think about.
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Post by T2 »

-woody,
yes it is difficult for me to accept that someone would go to all that trouble with an EV and then intend to drive stick. Else why publish a graph showing the expected performance of each of four gears ?

This vehicle needs but two gears. Second gear and reverse gear. Reverse gear has its original control interface already in place.

Electric reverse although seeming much easier at first with AC will take more work with interlocks etc. The presence of a gear shift saves all that messing around. If you've already got it why not use it ?

- Richo, What selection criteria did you make for 110Vac 50Hz ? Otherwise to me this just looks like something the rewinder has already done before for a commercial customer, and more importantly something he can test afterwards and therefore confidently guarantee. Offer to leave your inverter for testing if possible.

Will second gear get you 110Km/hr at around 7200 rpm ? Then 240Hz @ 400Vac or 1.66V/Hz would be my choice. However you seem set on 110/50 = 2.2V/Hz.

It is as well to consider that a decision for a somewhat lower voltage battery pack later on will make this this motor unsuitable. Again on second thoughts I would advise against laying out any cash at all on a rewind until your electrical and mechanical installations are proved out. Moving around at golf cart speeds will test the robustness of that particularly long string of cells and let you judge the effect of sustained 3600 rpm in second gear and Mobil ONE on the gearbox.

- Nevilleh, since you brought it up, I like the idea of an upconverter also. I happen to have a 400A 90 microhenry inductor lying around from a Willey DC armature controller. At 4khz operation it's not that large. Less than a 10cm cube. Although you are going to need an additional full size capacitor bank for it to draw current pulses from.

Interfacing any industrial controller to an existing DC supply brings its own unique problems. Spoofing the controller into believing it has genuine AC and that the DC bus voltage lies within specs are usually necessary.

I commissioned and then rejected a free offer of a Commander 15Kw drive with motor w/ integral tach and all comm cables. On the bench it performed well but... It took an hour to figure out how to disassemble to gain PCB access for our digital camera.

The First drawback was it wouldn't go above 120Hz and Second the realisation that should it fail, after going to some length to spoof all the input circuits, there would be NO schematics and probably no tech support available for a 1999 vintage drive. Plus software ran only on Windows '95 machine LoL. Also up close a 15Kw system is huge but still ONLY 15Kw with perhaps a 50% overload. Not only you end up dead in the water and re-engineering a new drive but at that point a Curtis or a Wavesculptor minus all the messing around start to look like a much better deal.

I'd give Curtis a second chance. I know their DC drives were sometimes abused by EVers in the early days with 72 volt systems driving 28v 400 Amp ASGs. Above 36 Volts on the armature, an aircraft starter generator runs really hot. We measured 2200 watts of iron loss with full field @72v and 4500 rpm, this explains why they were driven around in top gear pulling max current but at low output voltage, I saw a youtube where this practice continues, can't recall which controller but it was unmistakably an ASG but now with a LiPo battery rather than Pb-acid. The driver mentioned keeping the car in third gear permanently while in the city. Pushing the drive towards current limit is clearly not good practice and will put added stress particularly on an air cooled drive.

-Richo, Good success and that's it finally final.
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Post by Nevilleh »

Richo, can you put up the details of your looking into a boost converter? I'd like to see what you did.
I'm thinking of converting my dc motor powered BMW to an ac motor and wondering just what to do and what to use, so I need all the help I can get. I'd like to stick with my existing battery pack and of course, my very own bms, far superior to any you might find in an MX5. Image And my charger, likewise. That all means running an ac motor from a nominal 144V and I think putting my effort into a boost converter might be the way to go, rather than re-wiring 135 cells in series giving only 432V and hence having to re-wind a motor.
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Post by weber »

T2 wrote:yes it is difficult for me to accept that someone would go to all that trouble with an EV and then intend to drive stick. Else why publish a graph showing the expected performance of each of four gears ?

This vehicle needs but two gears. Second gear and reverse gear. Reverse gear has its original control interface already in place.

Electric reverse although seeming much easier at first with AC will take more work with interlocks etc. The presence of a gear shift saves all that messing around. If you've already got it why not use it ?
If you've already got multiple forward gears, why not use more than one of them?
Last edited by weber on Wed, 11 Jul 2012, 04:35, edited 1 time in total.
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Post by Tritium_James »

Nevilleh, don't forget your boost converter needs to be bidirectional, as you need to handle regen energy too. It's not completely trivial.
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Post by Nevilleh »

Tritium_James wrote: Nevilleh, don't forget your boost converter needs to be bidirectional, as you need to handle regen energy too. It's not completely trivial.


Quite right, I am merely speculating at present - probably a dangerous thing to do!
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Post by Richo »

T2 wrote: This vehicle needs but two gears. Second gear and reverse gear. Reverse gear has its original control interface already in place.


Ah well you say constant power is not important.
I cannot drive in 2nd at 100kph as the RPM would be a bit high.
I cannot drive in 4th at 100kph as the continuous power cannot be maintained.
So realistically I would need 3rd and reverse.

But If I were going a set reduction drive I would not use this motor.
I would choose a bigger one for better acceleration and better coninuous power handling.
So the short answer is NO but the long answer is YES.
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