# AC motor requirements



## Sunking (Aug 10, 2009)

Let's see if I can help. DC motors are really simple to control. In a Nut Shell all you do is vary Voltage to control speed and power. The Controllers used on DC motors are very simple Pulse Width Modulated DC Controller. Think of them as an On/Off switch. They just connect the battery to the motor in on and off or Pulses. At 100% modulation, the controller just connects the batteries directly to the motor for Maximum Smoke. At 0% modulation is and open circuit or disconnect the battery from the motor. 

AC motors and their controllers are Variable Frequency Inverter. Speed on an Induction, BLDC, and PMACis controlled by Frequency. Much more complex than a DC controller and *NO* they are not compatible with DC controllers.


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## electronmonk (Oct 30, 2014)

On the UQM motor/inverter sets, and other AC motors, the inverter is what controls the motor.


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## dougingraham (Jul 26, 2011)

rp0029 said:


> I'd prefer to have an AC because I would really rather not run a transmission, and I like the regenerative braking. When I look at the DC system, say a Warp motor is about 1800-3k (depending on what size you get), and a Zilla 2k or so.
> 
> With the UQM, would I still have to buy a controller, or does the inverter function as the controller? If I need an additional controller, what is the cost of that?


Having to run or not run a transmission has nothing to do with AC or DC motors. It has to do with torque and what is an acceptable acceleration.

In this case the inverter is the speed controller. You would not need an additional device.

Generally, if you keep the transmission you can get by with a lot smaller motor. If you eliminate the transmission you need to do a better job of engineering so that the tire diameter/rear end ratio/acceleration/top speed all come out the way you want them too. If you keep the transmission there will be a gear that is close enough to make it work out.

The OEM's don't have transmissions but they have chosen their motor/controller/voltage/current/top speed/tire size/rear end ratio very carefully so it all works out. In a DIY environment you don't have the option to pick some of those things. I had the opportunity to drive a direct drive DIY project a couple of years ago. And it was powered by an HPEVS AC-50. It was a Morris Minor and it had been lightened a lot. It was a pleasant vehicle to drive but no way could it be called exciting. This vehicle was owned by John Bishop and was converted by his brother Mark. Mark had a 1st gen Honda Insight he had converted at last years EVCCON and while I didn't get to drive or even ride in it, the car seemed to get around nicely. You will either need a lot of torque over a wide RPM range or a very light roller (or both) if this is going to come out the way you want.

Best Wishes!


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