# AC Controller/motor matching?



## buzzforb (Aug 16, 2008)

I have noticed that all ac setups come as a matched unit. If i am able to build an AC Controller based on an upgraded Circuit cellar design, Will i be able to match it to any ac motor that fits requirements? Also, Has anyone looked at used traction motors. They seem to be readily available. LAST Question!, What do you need to do to add regen to a diy controller? Is it just in th programming?


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## xrotaryguy (Jul 26, 2007)

You can actually run various different motors on different controllers as long as the controller has the right hardware (ie. voltage rating, amperage rating on the power transistors). You would need to do some programming to tell the controller the characteristics of the motor. 

So, if you build something similar to the circuit cellar design, then you should be able to run what ever motor you want. You might need to build a reluctor and hall sensor setup though. I don't recall how the circuit cellar guys did that.

Some controllers for smaller AC induction motors like the ones found in lathes and mills etc can figure out the characteristics of the motor semi-automatically. However, those controllers rely on a resistor inline with the motor's "power wires" and that's not really practical with a motor that might pull 200 amps or more.


I personally think that used traction motors are the way to go for this type of thing. They're so darn cheap. I got my 15 hp ACIM for about $100. probably about 12 times less expensive than a comparable series wound DC motor. This is the biggest reason why I want to build this controller.

Regen does require a certain amount of programming of course. It also requires a little bit more hardware. You'll need one more IGBT or other suitable power transistor and related drivers etc. to control how much power is sent to the battery pack during regen. There may be more to it, but that is my understanding of it at this point.


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## epyon (Mar 20, 2008)

I would love to use a AC motor . I can get a 10-25hp motor for close to nothing , but the controller ,what should I do and or get ? What part number should I be looking for ? Could I use a 12vDC to 120ac converter to power a plug-in controller to just get going til I save up for a one off unit ? Or is there another way to have a AC motor controller ?


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## buzzforb (Aug 16, 2008)

I am still new to the game, but from what i understand so far, you must have both and inverter and a controller to use an ac motor in an ev application. The inverter is what turns your dc current into usuable power and the controller section controls the sine wave sent through these inverters in such a way as to give you speed control. If you read other threads you will see that getting an ac motor to run an ev can ve very complicated, but once you have got the thing working, it is by far the best option. You will hear some talk of BLDC motors(brushless DC) being a good alternatve. The problem with these are twofold; 1.) They have to have a controller that is basically as complicated as an ac controller. 2.)They use rare earth magnets in the buiding of the motor, so this somewhat negates the notion of a cleaner less impactful transportation option. What i mean is, if we all started driving cars with rare earth magnets in them how long before we run out of the RARE-earth magnets.


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## major (Apr 4, 2008)

xrotaryguy said:


> Regen does require a certain amount of programming of course. It also requires a little bit more hardware. You'll need one more IGBT or other suitable power transistor and related drivers etc. to control how much power is sent to the battery pack during regen. There may be more to it, but that is my understanding of it at this point.


Hi xrot,

With the 3 phase inverter bridge you do not need "one more IGBT" to get regeneration to a battery source. The extra IGBT is only needed if you want to use dynamic braking where the energy is dissipated in a resistor.

Regards,

major


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## frodus (Apr 12, 2008)

In AC systems, the Inverter and the Controller are the same thing. You're right, the inverter converts the DC to an AC signal, but inside the inverter you're actually changing the frequency to each of the phases. 

This type of inverter is called a Variable Frequency Drive. This is NOT the same type of inverter you use to supply an AC device off 12V. Another thing, you'd need a 3 phase motor, and MOST of them do not run off 120. They're made for 208 or higher voltage phase to phase. The inverters you're thinking of are only one phase, line to neutral.

Also, you're going to need a really high voltage (lots of bats in series) to use most inverters. There are some AC systems, look at http://metricmind.com/

Its not trivial to make AC from DC and to control the vectors for phase angle correctly. You also have to limit current and voltage while you're doing this.


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## buzzforb (Aug 16, 2008)

What would be the best and most readily available ac motor to convert an ev with. Its so amazing that there are no real options specifically for ev applications. Please be as specifi as possible since there is such a wide range of choices.


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## frodus (Apr 12, 2008)

go to metricmind... we won't do the chosing for you.... it all boils down to cost. Its not our decision. You know your requirements, so its best that you make the decision.

all of those were made with EV's in mind.... as in... designed for EV use.


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## buzzforb (Aug 16, 2008)

I didn't ask you to choose for me. I was asking for a set of parameters for choosing non 8,000$+ motors from metric mind. I thank victor for his contribution to the game, but i don't necessarily want to fund his ev vehicles. I was hoping to find used industrial ac motors that would be usable in ac conversion.


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## frodus (Apr 12, 2008)

buzzforb said:


> I didn't ask you to choose for me. I was asking for a set of parameters for choosing non 8,000$+ motors from metric mind. I thank victor for his contribution to the game, but i don't necessarily want to fund his ev vehicles. I was hoping to find used industrial ac motors that would be usable in ac conversion.


actually you DID ask to chose a motor for you....



> What would be the best and most readily available ac motor to convert an ev with.


go to an industrial supplier

good luck finding a DC powered inverter for your application....


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## 1clue (Jul 21, 2008)

Buzz,

There are a lot of problems in finding a good AC motor for a low cost. IMO, if you are just looking because you don't want to spend that much, then I suggest you watch ebay and other similar sources, and some year you might find something interesting.

If you're looking because you want high quality and you don't have the cash, but have plenty of time and patience, then maybe you could either find a motor which is close but not quite to requirements and rewind it, OR you could find some stator plates and machine up your own motor. In either of those cases, by the time you get done you will have spent WAY more in time and effort than you would have spent cash on a spiffy new motor.


There is an open source hub motor team going right now, I think they've gone to an extreme by wanting not only to make their own motor from scratch, but make it direct drive as well.

You don't have to go that crazy to build your own motor. Start doing research and see what it takes. That's what I'm doing, I joined up with rcgroups.com and have ordered a couple small airplane motor kits so I can see what's involved. Then, if I'm still interested, I might just find some stator plates online somewhere...

Good luck.


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## buzzforb (Aug 16, 2008)

Thanks 1clue for the helpful advice. I am looking at building both a motor and controller so any help is wonderful. I do have more time than money so I am doing as much research as possible. I wish i could get a cross section of some of the nicer AC models, OH WELL. Is there any reading on motor design that you or anyone else can recommend. THere is just too many talented people roaming these forums for there to be so much of a vaccuum for reasonably priced well designed AC systems. Perhaps its condescending attitudes from the likes of Frodus that keep it from happening. THe hub motor is a great idea, but it seems they are jumping a couple of steps. Why not get together and design an AC motor that is well suited like those from metricmind. What do I know, I am just a junior member.


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## 1clue (Jul 21, 2008)

Buzz,

I'm a n00b too, I just type for a living and so I'm pretty quick at it.

I'm nowhere near ready to design a motor. I started browsing rcgroups.com as I mentioned in the last post, and eventually started posting questions. They have a really good cdrom tricks thread right here:
http://www.rcgroups.com/forums/showthread.php?t=240993

The focus of that site is making models, and the focus of the section I specified is electric motor design and construction. So far, it's easily the best electric motor forum I have found. Most things are focussed on CDROM motors and winding from kits, but there are some truly knowledgeable guys on there who are designing their own stators and machining their own parts, and using numbers to do it.

This might not be the place to learn it all, but it's a good place to start I think. It will let you get your feet wet with a kit, the way I am doing right now. I'm waiting for a gobrushless.com kit to show up, and then I'll start winding motors.

Regarding netiquette and such, chill out a bit. Some people don't type well, and others don't realize that they come across as a bit unpleasant. They really could be that way, but chances are if you meet somebody who just seemed slightly off, you'd find out it was just a quirk of the way they type.


Back to winding motors, I figured I would start out small and make something I know to be a sound design first. I'll probably wind that one a few times and then put it on a model, and then step up to something a little bigger. A lawn mower or a bicycle maybe. I've heard good things about the possibilities of a ceiling fan motor being rewound as an outrunner.

I agree that the OS thread seems to be skipping some things, but again I don't know enough about it yet to say for sure.


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## buzzforb (Aug 16, 2008)

What limitations does this design have in larger applications?
http://www.aerodesign.de/peter/2001/LRK350/Warum_dreht_er_so_eng.html#Anker1164462

It might be of some help to the wheel hub boys.


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## 1clue (Jul 21, 2008)

It's called an outrunner, and while it does slow the rpm down a lot it doesn't really increase torque that much.

It's possible to get a whole lot of torque from an outrunner, but not 7x as much, the way it does the speed reduction. The torque is related to the number of magnetic lines of force going through the air gap (that's not quite right, but simpler than I can think to word right now) and the radius of the motor, I think again the air gap is basically what the critical point is.


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## buzzforb (Aug 16, 2008)

Check out this site.
http://www.burgessnorton.com/Soft Magnetic Composites.htm
It would be nice to get these guys to make a stator or rotor for a custom motor. Kills all the difficulty with laminating.


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## buzzforb (Aug 16, 2008)

What would it take to rework an industrial ac motor for higher rpm use, assuming that there is an ac controller in place that is able to run the motor at higher frequencies.


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