# AC Motor question



## Tractionlimit (Aug 20, 2010)

I began looking for a go-kart motor, when I came across this:

http://currentevtech.com/Drive-Systems/Curtis-Motor-and-Controller-Kits/AC-20-p85.html

I haven't been able to reach anyone at Currentevtech yet, so hoping somebody here could help me. 

Is this a true AC EV motor, meaning will it handle regen and high RPM operation? A motor weight of 53lbs making 75hp and 105ft-lbs seems way too good to be true. 

If these specs are true, it might actually work well for a motor-per-wheel performance AWD EV (260lbs of motors and controllers making 300hp/420ft-lbs peak?? total cost=$15K) What am I missing here?


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## Tractionlimit (Aug 20, 2010)

^ I can only guess that this was a typo... 

Other sources quote the AC-20 at 46hp, 110ft-lbs and 54lbs weight. Still not bad to power a single wheel in an AWD system. Thoughts?


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## major (Apr 4, 2008)

Tractionlimit said:


> ^ I can only guess that this was a typo...
> 
> Other sources quote the AC-20 at 46hp, 110ft-lbs and 54lbs weight. Still not bad to power a single wheel in an AWD system. Thoughts?


Hi Tlimit,










This curve does not jive with the other specs. Yeah, I know it is at 48 volts, but nevertheless, the torque curve would indicate something screwy with those specs.

Buyer beware 

major


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## Tractionlimit (Aug 20, 2010)

^ are you refering to the way that the torque curve drops off at 2K?


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## tomofreno (Mar 3, 2009)

> are you refering to the way that the torque curve drops off at 2K?


 I think major is referring to the max torque in the curve being more like 75 lb-ft, and max power about 25 HP. The max power could be increased somewhat (but not doubled) with higher voltage, but not the max torque. Note that the quote from currentev is regarding the CONTROLLER capabilities, not the motor.


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## major (Apr 4, 2008)

Tractionlimit said:


> ^ I can only guess that this was a typo...
> 
> Other sources quote the AC-20 at 46hp, 110ft-lbs and 54lbs weight. Still not bad to power a single wheel in an AWD system. Thoughts?


Hey Tlimit,

To follow up on this a bit. tomof is correct. The torque curve is well below the spec. And even with higher current. And take that 1800 RPM point from the curve. Shows 72 lb ft of torque. Gives 24.67 hp which is close to the hp curve. Equals 18409W. It also shows 710 Amps DC at that point. At 48 volts, that is 34080W input. Which figures to 54% efficiency. Great 

Just for kicks, look at the AC50 spec. Says 115 lb ft for torque. Look at the pdf graph for it. Only about 90 lb ft max.

This is just another example of vendors of EV motors not giving any decent design information for customer to properly apply the products or make intelligent purchase decisions. I see this time and time again. It sucks 

So, buyer beware.

These motors may well be very good, and in fact at least one of the competitors in the NA TTXGP ran such on his bike, #37 (Norton) IIRC, and did really well with it, after ironing out some thermal issues at the first race. 

Regards,

major


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## frodus (Apr 12, 2008)

I think either the AC15 or the AC20 is going to be PLENTY for a go-kart. People are using them in much heavier vehicles (like motorcycles and threewheelers) with great results. Not only did the Norton team use an AC20, but the Volt (Thunderstruck motors team), Native (electric motorsports team) and the Squarewaveracing all used an AC15 or AC20 on their bike with great results. I think the teams had more problems with getting enough power from the batteries than anything else. The thermal problems were to do quite a bit with the controller not being properly mounted to a heatsink/propperly cooled and going into thermal cutback.

Once the solved the thermal problem, the only issue that remained was lack of power from the batteries. I know the Norton team had Kokam batteries which had plenty of power, and ended up with a podium finish at least once.

They've got a lot of torque/HP for the size, but I'm with Major, I've always ignored those torque curves. I think some of the values are mixed between the controller and motor. It really needs to be properly Dyno'd.


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## Bowser330 (Jun 15, 2008)

hopefully Dave K. will chime in and help straighten things out...


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