Converting a gas Quad to AC

Technical discussion on converting internal combustion to electric
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peskanov
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Converting a gas Quad to AC

Post by peskanov » Mon, 24 Oct 2011, 14:14


Greetings from Spain! A friend and I are trying to build a light AC vehicle, our first EV conversion in fact.
I have been reading this forum for some time, as it seems AC EV systems are popular only in Australia (AC motors are my technological fixation I guess).

The new, cheap Kelly AC controller seems the perfect way to start, so we got the 72V/200A model. We are also getting an small 48VAC motor for testing it.

Now we are looking for the rest of the EV components; I am posting here to receive some advice/criticism on my setup. Here is my list:

- Vehicle: a Quad, probably a 300-500cc one. Still looking for it, any sugestion on specs?

- Batteries: 24 cells, Thundersky 20 Ah (2 or 3 in parallel, 24 series). 20Ah cells have a good price now on GWL/Power shop.
   http://www.ev-power.eu/index.php?p=prod ... 20ah-promo

- Charger: KP-E 72V, 24S, 6A.
   http://www.evassemble.com/index.php?mai ... cts_id=173

- Controller: Kelly 72V/200A.
   http://kellycontroller.com/kim722024v-7 ... -1048.html

- Transmision: direct, chain transmission. Ratio 1:5

- Motor: Industrial AC, alluminium, 2 pole 5.5 kw. Rewound to 36V(?).
Looking to this one:
   http://www.inverterdrive.com/group/Moto ... fault.aspx

My wish is to reach 12 Kw peak with the motor. We are not very interested in high top speed, I think 45-60 kph should be enough.
Would be a 5.5 Kw, 2 pole motor (rewound to 36VAC) up to the task, or maybe an smaller 3 Kw one is enough?
Is it possible to rewind a high voltage / low amps motor like that one to low voltage / high amps?
What is the best voltage (when rewinding the motor) for this controller? With 24 cells I get 77V nominal, 88V max. = 55V AC. I understand that rewinding to lower voltage I can get more power (at higher rpm).Which voltage would you choose?



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Johny
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Converting a gas Quad to AC

Post by Johny » Mon, 24 Oct 2011, 14:36

Hi. Just need a little more detail. Can you tell us the motor RPM for 60km/hr please. That way the transition from constant torque to constant power can used in the calculations. Alternatively the tyre diameter or tyre specification. Eg. 165/65R13.

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Converting a gas Quad to AC

Post by peskanov » Wed, 26 Oct 2011, 00:43

Johny,
We are still looking for the Quad; I think we could get a Polaris Predator 500, there is a stock of broken ones near here.
If I am not mistaken, the tires must be something like 20x11-8.

When I made the calculations for the transmission, I was only making approximations based of maximum 4500 rpm (for a 2 pole motor).

If I top at 70 km/h with an 8 inches wheel, that means 915 rpm at the wheel. For a 4500 rpm motor, the relation is aprox. 1:5.
I used 10 km/h as margin, so 60 km/h would be the target speed.

I ignore eveything about transition from constant torque to constant power. Is it related to the point where power and toque curves cross?
Is there any good article/book where I can read about it? I have the Bob Brant "Build your own EV" book, but did not found anything about it.

We got an 1.5 Kw 48 VAC motor for testing. I think we will start testing the Kelly controller this weekend.

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Post by Johny » Wed, 26 Oct 2011, 17:33

OK. Working on a final ratio of 5:1 and a wheel diameter that gives us 4500 RPM (motor) at 60 km/hr.

5.5kW 2 pole AC motor. Assume breakdown Torque 3.5 times nominal.
Controller limited to 200A
Vehicle weight 350kg (assumption includes driver)

Motor rewind voltage 80 VAC Star/46V Delta and run in Delta.
50km/hr in 5.6 seconds.
60km/hr in 7.6 seconds.

Edit: Fixed incorrect figures and remnoved incorrect statements.
Last edited by Johny on Wed, 02 Nov 2011, 08:23, edited 1 time in total.

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Post by Johny » Wed, 26 Oct 2011, 17:48

peskanov wrote:Is there any good article/book where I can read about it? I have the Bob Brant "Build your own EV" book, but did not found anything about it.
Sorry, I didn't answer that. We rabbited on about this on this forum for quite a long time. See this topic. There are others.
viewtopic.php?keywords=rewind&t=585&start=1

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peskanov
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Converting a gas Quad to AC

Post by peskanov » Fri, 28 Oct 2011, 14:05

Ok, one question about acceleration using a 72V AC motor. The controller is 72V DC. To get nominal power, isn't necessary to have sqrt(2) * AC voltage? That is, ~100VDC?

We would be more than happy with the acceleration you calculated for 4 poles / 50VAC. But what about gearing in that case? Should we use 2:5 instead of 1:5, for the 4 pole motor?
Or the calculation was made for 45000 rpm at 60 km/h?

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Post by Catavolt » Fri, 28 Oct 2011, 20:06

you could use one of my 112M frame motors used in this video http://www.youtube.com/watch?feature=pl ... 9fi7AZmRVE

Catavolt AC 112M 72v 15kw cont peak45kw 7500rpm $2600AUD complete with controller.
Last edited by Catavolt on Fri, 28 Oct 2011, 09:09, edited 1 time in total.

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peskanov
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Converting a gas Quad to AC

Post by peskanov » Mon, 31 Oct 2011, 08:13

That's one mighty garden tractor! Image
Unfortunately our whole budget fo this thing is ~4000 AUD.
A local technician is asking us 250 AUD for rewinding a 5.5kw motor. I think it's good price, but I am still a bit confused about the best motor configuration matching the kelly 72V/200A controller.

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Post by Johny » Mon, 31 Oct 2011, 13:46

I am away from the PC where I set up the spreadsheet until Wednesday but the figures I presented earlier are about about the best I can give you anyway. As you lower the motor voltage, the controller current goes up. Increase the motor voltage and your top speed (well at least the speed where you lose a lot of torque) comes down.

So it's a comprimise between:

1. low top speed with good acceleration (keeping just below controller limit)
   and
2. good top speed but slow acceleration (due to being on the controler current limit).

Keep in mind that I have made a LOT of assumptions about the motor and the vehicle so you should get someone else to verify a numbers that I have given.

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Converting a gas Quad to AC

Post by peskanov » Wed, 02 Nov 2011, 15:04

Johny,
your advice is appreciated. Ev conversion is basically non-existent in Spain, that's the main reason to wander in a Australian forum, so far from these lands. Any help is welcomed!

Following your advice, now we are looking for a 48V, 4 pole 5.5KW motor. Suppliers are quite puzzled when earing our demands...I guess a rewind will be necessary after all...

Some pictures of our work. We are collecting the components for a test now.

That's the Kelly KIM, an inexpensive, light an small controller imho. Our model is the 72V/200A one.


Image

Image

We got this motor for testing. It's 3 phase, 48VAC, 1.5 KW. This voltage is extremely rare here. Even the supplier of this motor seems to be unaware its existence. Image

Image

Looks aluminium to me, is quite light; seller didn't know.
Here's is the data.

Image

The windings; looks like 1 mm wire. The motor is rated at 30A nominal.

Image

We left the motor in the machine shop; we need the shaft drilled to fit the encoder. It seems the controller cannot work sensorless, unlike many small industrial inverters we have used.

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Post by Johny » Wed, 02 Nov 2011, 15:50

Hi Peskanov.
Yes a motor that low in voltage would be uncommon. Some of the later forklift that use AC motors would be close but they would be hard to come by I think.

I can't quite work out if that is a 1400 RPM motor but I'll assume it is.
A 1.5kW nominal, 50Hz, 1400 RPM motor (Tmax/Tn=3.5) running in 48V Delta) should give you:

Km/H Seconds
10    1.119
20    2.598
30    6.317
40    16.711 (3000 RPM)
50    1117.044
60    3894.822 (4500 RPM)

It's kind of showing you that about about 3000 RPM the torque drops off so much that it won't go any faster.

Have you got an estimated vehicle weight including driver? I am still basing figures on a guess of 350kg.

Given your 12kW controller limit, somewhere around a 4kW motor should give you similar performance.

BTW I have been horribly pessamistic about the acceleration for the 5.5 and 4KW. I did not change the motor current in accordance with the changing motor voltage so your 50km/h figure is closer to 6 seconds (sorry).

Let me know when you have some motor figures such as voltage, current and nominal and max torque (of course poles and RPM).

I'm kind of basing the guess motor on ABB motors (for torque) and multiplying the current by the ratio of reduced voltage.

(Figures courtesy of "Woody's" speadsheet.)

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Converting a gas Quad to AC

Post by Richo » Wed, 02 Nov 2011, 20:52

72Vdc controller -> 50Vac
50Vac controller / 48Vac motor = 1.04 x
So unlikely to peak more than the 1400 RPM. (3000RPM max for top speed?)

I'd go with a higher voltage controller.
260Vdc would be more the go...
Hard to find!

Still could get peak more like 15-20kW
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Post by Catavolt » Wed, 02 Nov 2011, 21:26

You could of used a SKF sensor bearing , no machining necessary.
http://www.skf.com/portal/skf/home/product_pages
They work fine with a Kelly controller , also the Tritium and curtis.

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Post by Adverse Effects » Thu, 03 Nov 2011, 03:26

its a pitty you have all the stuff allready

http://www.goldenmotor.com/ has everything you need but most of it is BLDC

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Post by peskanov » Fri, 04 Nov 2011, 14:03


Johny,
this test motor is a 1400 rpm one, a 4 pole. You can check the motor data in the 4th picture.
Thanks for re-checking your calculations, the numbers looks very promising for a small budget project like this one.
We don't plan to use the test motor in the Quad; we have another "mule" to test the components.
I don't have a picture of our "mule" here, and I don't even know how this things are called in English. It looks like this (but much much older):

Image

The plan is to learn how things work with this little machine and then buy the Quad, the battery and the motor (the real one).
We don't have a weight estimation, but I would like to limit weight to 300 KG (driver included).
The battery should weight <40 KG, we plan to use thundersky ( or sky energy or whatever is called now).
Motor specs at inverterdrive.com are 35 KG for a 5.5KW 4 pole, and 31 KG for a 4 KW one.
One of our problems is related to the length of the motor, so we will delay buying the motor until we buy the Quad.


Richo,
I'd go with a higher voltage controller.
We started this conversion just because I saw the Kelly KIM; it's so cheap it makes the whole thing affordable for us.
I agree higher voltage would make a more interesting Quad, but that's all we can get Image The biggest chunk of our budget will go into the battery.
The question is, which motor/gearing do you think fits better this controller?


Catavolt,
You could of used a SKF sensor bearing , no machining necessary.
I was unaware of the existence of the sensor bearings. That looks like a perfect solution for the definitive motor, we will try to get a quote.

Adverse effects,
its a pitty you have all the stuff allready

http://www.goldenmotor.com/ has everything you need but most of it is BLDC
I kwnow Golden motor, some time ago I was interested in their "golden pie" hub motor. The idea of a hub motor with the controller embedded appealed to me.
Their PM motors looks also nice, but I find induction motors more interesting. It's just a question of playing with the technology I like.
I am not sure EVs can be successful using neodymium magnets; the element just seems to be too scarce.

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Post by Johny » Fri, 04 Nov 2011, 14:47

peskanov wrote:The question is, which motor/gearing do you think fits better this controller?
Your 2 pole 3000 RPM motor starts dropping off torque around 3000 RPM which is about 40 km/hr with the 5:1 gearing.
Even so, a 4 KW would still get you to 60 km/hr in 7 seconds and 80km/hr in 17 seconds - which makes it sound about right to me - I'm assume that 80 km/h would be pretty scary on a small quad.

Most of the torque would be required 0 to 40 km/hr which is where it sits with a 2 pole motor geared to do 4500 RPM at 60 km/hr.

For 60 Ah cells I make the pack weight about 60 kg.

I's all a comprimize between available controller current, meaningful top speed and low speed torque (climbing ability and acceleration).

This is the acceleration graph for a 4 kW 2 pole wound to 46 Volts Delta. 350 kg vehicle with 24 x 60Ah cells and 200 Amp controller limit. Final drive arranged for 60 km/hr at 4500 motor RPM.
Image

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Post by Adverse Effects » Fri, 04 Nov 2011, 15:49

i was thinking more of thes ones

Image
Last edited by Adverse Effects on Fri, 04 Nov 2011, 04:50, edited 1 time in total.

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Post by peskanov » Tue, 22 Nov 2011, 15:59

Adverse effects,
yep, I knew. For some reason I dislike neodymium motors; maybe because I like to use a technology I can also advocate. I can't imagine mass production of these things, neodymium is too rare.


Some updates in the project now, for everybody.

We got 2 prices for 5.5KW motors rewound to 48VAC (from the same company):

- 3 phase 48v B-3 frame-112 7,5 HP 1400 rpm axis 28mm 307,85E (422 AUD)

- 3 phase 48v B-3 frame-132 7,5 HP 1400 rpm axis 38mm 366,99E (503 AUD)

Reading the previous posts, I understand we can go for the small frame one, it should be powerful enough to match the controller. Any opinion?

We are also trying to buy a broken motor Kawasaki 250 quad. Curb weight is 182 KG. I will post pictures and specs if we reach a deal with the owner this weekend.


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Post by Johny » Tue, 22 Nov 2011, 16:11

Hi Peskonov. Can you get nominal and peak (breakdown) Torque figures on these motors. Also weights. The smaller frame will almost surely have less peak torque. Of course, since it's probably lighter you may not care about that anyway.
Either motor will see you sligtly controller-limited so it's really down to weight and torque - and price Image.

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Post by peskanov » Wed, 23 Nov 2011, 15:26

That's all the data I have from those motors, until now. It's difficult to deal with local providers, they will not make real money from selling a single small motor to a pair of hobbyist, and they don't have any kind of curiosity about EV conversions :(
I will post more data, at least they should give me the motor weights. I guess the motors have aluminum frame, it seems to be the usual one in the factory where my friend works.
Imho the big frame (132) seems too much for a Quad. The axis is 38 mm diameter, good for a car's transmission but I think it's a bit of an overkill on a 200KG vehicle.

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Post by Johny » Wed, 23 Nov 2011, 15:37

peskanov wrote:Imho the big frame (132) seems too much for a Quad. The axis is 38 mm diameter, good for a car's transmission but I think it's a bit of an overkill on a 200KG vehicle.
I agree. I use a 132 frame in my car to move 1000kg. As per my earlier posts, I think that a 5.5kW is overkill as well. A 4kW will give the same performance given the controller. Anyway, you have effectively answered your own question. Use the smaller motor - the difference in performance would be marginal.

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Post by Johny » Wed, 23 Nov 2011, 16:16

5.5kW, 4 pole (1400RPM) motor assumed to be 36NM Torque and Tmax/Tn = 3.1.
Here are some projections. The higher acceleration also translates to better hill climbing ability. The rewind voltages are for Star but apply equally well if the motor was rewound to Delta for that voltage.

Rewind to 48V
Image
The gradient ability is
10km/h 1 in 2.2
20km/h 1 in 2.3
30km/h 1 in 4
40km/h 1 in 7.3

Rewind to 36V
Image
The gradient ability is
10km/h 1 in 2.9
20km/h 1 in 2.9
30km/h 1 in 3.6
40km/h 1 in 5.3

Notice that the 48V gives better torque low down but a lower "top speed".
The 36V gives lower torque but a higher speed range.

Going up in voltage would improve the low speed torque further but you would lose higher speed torque.

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Post by peskanov » Mon, 28 Nov 2011, 03:59

That 36V curve looks very tempting! We will ask if we can get the motor in 36V; I am pretty sure that request will be something unheard of, here in Spain :D
Thanks for your efforts Johny, I owe you a beer.

Recent advances: we got a donor vehicle! It's an old (but famous) machine, a Kawasaki 250 mojave. Pictures first, info later:

Image
Image
Image
Image
Image

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Post by peskanov » Mon, 28 Nov 2011, 04:18

Now, the specs:
We got this old Quad (15 years) for 400E (550AUD). Motor is broken; brake discs are rusty and the frame is also slightly rusty. However, it does not have any important damage, and the wheels are in good condition.

We have weighted it: 180 KG, 88.5 front, 91.5 rear (pounds: 397, 195 & 202). No gas in the tank.
Rear wheels are 46 cm in diameter (18 inches).
The gas motor has 5 gears. Chain transmission has 12 cogs in the small gear, and 40 in the big one.

There is little space for the electric motor; 132 frame is definitely discarded, and 112 will be a bit difficult.

That's all for now; any comment on motor & battery placement is welcomed.
Last edited by peskanov on Sun, 27 Nov 2011, 22:36, edited 1 time in total.

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Post by peskanov » Mon, 28 Nov 2011, 11:39

Today's last picture: my friend Vicent has disassembled partially the Quad. You can see the frame here:

Image

I think battery distribution is going to be a bit difficult...

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