Hemonster's ACIM conversion

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Johny
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Hemonster's ACIM conversion

Post by Johny » Fri, 21 Aug 2009, 19:05

Sparky Brother wrote:.... I personally like the two pole configuration for the advantage that it gives you in the range of 1400RPM to approx. 4000 RPM because this is actually the speed you need the better torque the most ....

I might have to find out a trustworthy rewinder to work this issue out ASAP. Someone in the Eastern suburbs of Melbourne? Anyone?
When I was investigating rewinds I just used the yellow pages. Prices were all pretty similar. Have you got any work contacts they may give you "mates rates"?

A rewind to 220 V will also give you 4 pole torque all the way to nearly 3000 RPM
This is what I have done with the Qin Wei motor that I bought.
The ATV58 will handle that voltage nicely.
For increased performance up to 60k/h you could consider star/delta switching - this could be added later if required.

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Post by woody » Fri, 21 Aug 2009, 19:10

Hi Sparky,

I think you'll need the gearbox, or at least the transfer case in low range.

15kW 2 pole is about 50Nm Nominal.

The motor will have overload of its own (T[max]/T[n] of about 3) - this gets to about 150Nm, not really enough for direct drive unless you have a very high diff ratio. (Compare the stock ICE torque, if it's about the same, direct drive will accellerate like you're in 4th gear).

If you rewound to 4 pole, you'd only lose speed, not gain torque.

So the cheap option is stick with it, through the gearbox.
Other options:

trade your 15kW 2 pole for a 15kW 4 pole (same power / half speed / double torque)
get a larger 2 pole (18.5, 22kW)
Buy a new ABB 15kW 4 pole (~AU$1000).
Buy a hat, accelerate leisurely, buy a "I may be slow, but I'm ahead of you" bumper sticker.

cheers,
Woody
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Post by acmotor » Fri, 21 Aug 2009, 19:31

Can a 2 pole just be rewound to be a 4 pole ? Is it that simple ? Does a 2 pole have a smaller rotor than a 4 pole ? (shaft is smaller dia as well ?) Anyone know ?

Just thinking...
If the motor was rewound for 4 pole 15kW motor at ~208V on that controller (assuming that is possible)....
~ 98Nm (~60A) torque cont 0-3000RPM and peak on that controller of 98 x 108/60 = 176Nm + the 2 sec 200%, so around 200Nm at low revs (assuming the 200% is an extra something over Ipk). This is not a lot for DD but rather solid torque once you are off the line.
(This is controller limited as motor could provide ~300Nm peak)
Star delta switching would help.

The 2 pole as it stands could provide ~49Nm cont 0-3000 RPM and peak on that controller of around pullout (say 3x) i.e. 147Nm plus a bit with the torque boost from v/f increase at lower revs. (the controller has some Amps to spare)

So on that controller, changes to the motor winding may not give much advantage.
The question would be if you go DD then is maybe 147-200Nm enough to drive the vehicle up the steepest expected curb ? Probably marginal.

I'll have a good feel for this... my rewind motor is due back Monday.

Need some Johny/Woody calcs rather than my scribblings though. Image

Damn, took too long to type, they beat me ! Image
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Hemonster's ACIM conversion

Post by acmotor » Fri, 21 Aug 2009, 19:41

If you go with the 15kW 2 pole, keep the gearbox and the clutch. It will make changing faster and less drama. I am guessing AC, with its flat torque, on a gearbox is not the same as series DC. You are more likely to use first gear at takeoff than stay in one gear all the time as many DCs do. IMHO
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Post by Johny » Fri, 21 Aug 2009, 19:50

woody is right. I didn't realise how much you will be controller limited if you do a low voltage rewind.
Sparky, can you give us final drive ratios (both high and low), wheel size and tyres and projected vehicle weight please.
Will you still have a high and low ratio if you ditch the gearbox?


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Post by Johny » Fri, 21 Aug 2009, 20:30

I have run some preliminary Feroza figures through woody's speadsheet.
Final drive 5.285 : 1
Wheel Dia 74.67mm (used 16" wheel, 205/83)
I've assumed vehicle weight to be 1300kg - probably too light.
50 of 20Ah SLA and the ATV58 controller.
woody - I used Hemonster's motor for 2 pole and ABB 4 15 at 380V star for 4 pole. Both 15kw nominal.

It shows the 2 pole performance to be terrible.
Not even quite making it to 90 km/hr.
35 seconds to 70km/hr
(this is strange considering delta sync to be 78k/h - just not enough torque???).

A 4 pole rewind gets it to 70k/h in 11.2 sec. and 90k/h in 15.9 seconds - really pretty good.

Of course, this needs verifying (and the vehicle is lightish)...

Edit: 4 pole is better at 440 to 450V star - can optimise later.

Last edited by Johny on Fri, 21 Aug 2009, 10:33, edited 1 time in total.

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Post by Sparky Brother » Sat, 22 Aug 2009, 02:36

[quote="woody"] Hi Sparky,

I think you'll need the gearbox, or at least the transfer case in low range.

15kW 2 pole is about 50Nm Nominal.


OK You got me scratching my head again! I realise that with the 2 poles I am headed to nowhere.

Retaining the GB is something that I dislike the most. However if I decide to jump on this train I have to say to any foot mounted motor(my one) goodbye. Also I will have to kiss goodbye my idea to install the motor in the gear box tunnel for improved gravity centre On top of that I will have to engineer a plate for the GB and having in mind I already sold the ICE coupled with the clutch ... Well you understand    Image

I wouldn`t say I am the most stubborn dude around but I still want it to be a Direct drive so two roots from there on.
1. I go and buy a 15kW 4p foot mount motor. Any prices anybody? Preferably locally made
2. Keep the 2poles chunk and figure out a suitable reductor to bring the Torque up to the desirable value of at least 300 - 320Nm. I doubt this last one will be the cheaper option Image Image Image . I`ll go tothe shed tomorrow and see if I have any chance to hack the Gear box to something a little friendlier.

Johny all your Feroza data is spot on. The kerb weight is actually 1250 kg and I already removed 200kg in brick`a brack Gear box included in this number. It actually weighs 60 kg. I have no idea about the Engine. Could be around 1000 - 120kg.

I am getting increasingly inclined to get rid of the back seats and the removable hard top which I guess will give me some 60-80kg less so;

200kg (if I don`t retain the GB)
plus
100 kg engine
plus
say 70 kg seats and hard top gives me a nice weight gain of 370kg

Knowing I can play with 2x 68kg for the passengers and somewhat 2x15kg luggage for the two passengers makes the numbers even nicer bringing the weight gain up to 536kg

Now, 1260-536=724       724+110kg motor+360kg Green Savers + 48kg Inverter +say 50 kg cables& clickity-clacks gets us 1278Kkg roughly.

I am sure I am forgetting something but it wouldn`t be a lot. so yes Johny if your calculations are right I won`t need to buy a "I may be slow, but I'm ahead of you" bumper sticker :-)

Image Image Image Image Image Image
Last edited by Sparky Brother on Fri, 21 Aug 2009, 17:18, edited 1 time in total.

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Post by Richo » Sat, 22 Aug 2009, 05:28

Try find your GVM.
Usually there is spare weight between the curb+5passangers and the GVM.
So the short answer is NO but the long answer is YES.
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Post by Hemonster » Sun, 23 Aug 2009, 17:43

acmotor wrote: If you go with the 15kW 2 pole, keep the gearbox and the clutch. It will make changing faster and less drama. I am guessing AC, with its flat torque, on a gearbox is not the same as series DC. You are more likely to use first gear at takeoff than stay in one gear all the time as many DCs do. IMHO


Why first gear ACMotor? I thought that was more to match the really poor torque response of a standard ICE engine, but even the ACIM 15kw 2pole can deliver 150nm peak (or maybe slightly higher) from zero rpm? As such wouldn't it be possible to start from say 3rd or 4th on the flat? perhaps even for pull out into traffic? or am I missing something?

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Post by woody » Sun, 23 Aug 2009, 21:12

Hemonster wrote:
acmotor wrote: If you go with the 15kW 2 pole, keep the gearbox and the clutch. It will make changing faster and less drama. I am guessing AC, with its flat torque, on a gearbox is not the same as series DC. You are more likely to use first gear at takeoff than stay in one gear all the time as many DCs do. IMHO


Why first gear ACMotor? I thought that was more to match the really poor torque response of a standard ICE engine, but even the ACIM 15kw 2pole can deliver 150nm peak (or maybe slightly higher) from zero rpm? As such wouldn't it be possible to start from say 3rd or 4th on the flat? perhaps even for pull out into traffic? or am I missing something?
150Nm in first is like 500Nm in 4th, so you'll be able to take off a lot quicker :-). With the gearbox you get to choose. Direct Drive you're stuck with one gear for all conditions.
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Post by antiscab » Sun, 23 Aug 2009, 21:25

gears multiply torque

unless your conversion is rather light, or the gear ratios in 3rd and 4th are unusually short, acceleration will be sluggish.

for comparison, if your petrol engine can do 150Nm at peak torque, try taking off in 4th, at full throttle, slipping the clutch to hold the engine at the rpm for peak torque.
taking off in 3rd or 4th in a EV conversion will be much the same from an acceleration point of view (minus all the noise).

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Post by acmotor » Sun, 23 Aug 2009, 21:44

Woody is on to it.
The EV will always start on the flat with low torque motor, just as you can slip the clutch with an ICE.
But if the torque of emotor < tailshaft torque was in 1st gear then it will be a slug.

That's where I have reluctance to go 2 pole with DD. The torque/revs don't work out without a gearbox. (Should be fine with one, but you will likely need 1st gear to 3000RPM since you'll not have the series DC pull at zero). I've no experience with the AC/gearbox arrangement, just DD (via transfer case) so it's IMHO at this stage.
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Post by woody » Sun, 23 Aug 2009, 22:09

2 pole itself isn't the problem - it's just that you need one twice as powerful as a 4 pole for the same torque, and the controller needs double the current for the same torque.
Gearing can fix this though: a 15kW 4 pole with a 4:1 diff shouldn't be much different from a 15kW 2 pole with an 8:1 diff.
So it's all a matter of juggling the parts you have and/or are available and your money to spend to work out what will be the best for what you want.
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Post by acmotor » Sun, 23 Aug 2009, 22:18

woody wrote: 2 pole itself isn't the problem - it's just that you need one twice as powerful as a 4 pole for the same torque, and the controller needs double the current for the same torque.


Yep. That's what I'm saying. Image

Let's put it this way... as long as you can get the ICE equivalent rear wheel torque by some arrangement, you'll be happy. Image
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Post by Hemonster » Wed, 04 Nov 2009, 01:00

Not much happenning in my land of AC, am expecting my 2nd baby at the end of this month ... serious time gobbler that one Image

I've also been rethinking how complexity and costs increase dramatically as the weight goes up. Also in particular the drop in the vehicle's efficiency as you try to pack more grunt to move more metal. Weight begets weight when it comes to EVs - until better higher density batteries in lighter packages arrive.

Added to that is the carbon footprint of each of the battery packs and cells within them that would have contributed to both pollution in China (though that isn't my problem so much), but also CO2 emissions. Although still estimate to be less (70% less??), driving an EV still emits CO2 - though this depends on how long the battery lasts between each battery change - say every 5-7 years for LiFePO4? Might be a lot less if the cyclic lifetime of the cells reduce dramatically at higher discharge rates.

Headway reckon their cells do >1500 cycles at 1C, but have no data for 3C cycling. Anybody have this information? It would tie up my PC and PSU for weeks doing this testing Image

I started with EV thinking at the very start with a 3 wheeler and still am keen to do one of those. I recently bought a crystalyte 5305 brushless motor off the local auction site here for a cool NZ$480 (including postage) - it was a steal, they retail at easily twice that. I got the motor laced in a 26" bike wheel, 7 gear sprocket, 48V 40A crystalyte controller, throttle, and wiring harness. Now I have a platform to test those Headway batteries Image

I love the idea of building a 3 wheeler. I've been reading up on building a 3 wheel HPV, but intend on doing so without the Human Power side of things and only use this motor. The great thing about these HPV designs is that they are strong and yet very light. I hope to make something of it, perhaps even register it as a motorcycle and see if I can take it up to 100km/hr (50km/hr typically) and use it daily. I've read in many places where the controller (modified) was capable in short burst to take 96V at 100A, which is a lot of power for something that weighs 200kg including the single occupant. It will be a tubular space frame, fully faired with hinging canopy as the main door.

It won't be a utility vehicle as much as it would a commuter and doing the groceries, and can't carry the family - but hey, they will still experience MY EV grin at the very least Image

In the mean time, I'll keep the AC conversion flame on low in the in the background - I'm sure I'll get to doing it one day. I'm still watching you guys over the ditch for inspiration, but for the time being I'll go off on this tangent for a wee bit.

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