# Making an AC motor controller



## aravindzzz (Jul 5, 2010)

I am an Electrical engineering student. As our final year project we are planning to make an EV. We are aiming to convert an old car into an EV. We got a small car which has things till the gearbox. We wanted to make the controller from scratch... soo any one has any ideas or any links which may help me in making a controller ?? We dont want the manufactured one.... we are aiming at buillding one ourselves....


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## Georgia Tech (Dec 5, 2008)

aravindzzz said:


> I am an Electrical engineering student. As our final year project we are planning to make an EV. We are aiming to convert an old car into an EV. We got a small car which has things till the gearbox. We wanted to make the controller from scratch... soo any one has any ideas or any links which may help me in making a controller ?? We dont want the manufactured one.... we are aiming at buillding one ourselves....


I know where there are there is an EXCLENT set of plans for a DC controller....
Look at Paul and Sabrina's controller. Called "Open Sourece controller" or "Revolt". Very GOOD controller....very good!!! But DC not AC...


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## Citystromer (May 2, 2009)

Yes, only you`ll need to build three of them, three power stages anyway for any AC motor. It`s possible, I´d be interested to read about specifications, such as PW frequency range ... Do they use around 18KHz like on DC motors?


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## few2many (Jun 23, 2009)

Theres a whole thread on a home brew ac controller around here somewhere. I've been keeping up with it, but I'm certainly not an EE.


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## Anaerin (Feb 4, 2009)

few2many said:


> Theres a whole thread on a home brew ac controller around here somewhere. I've been keeping up with it, but I'm certainly not an EE.


I don't know about around here, but I know there's some work being done on one by the makers of the Open ReVolt controller over at ecomodder: http://ecomodder.com/forum/showthre...eap-3-phase-inverter-ac-controller-10839.html


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## joamanya89 (Feb 13, 2012)

Have you got any thing about an AC controller? I would like to get some information to do it by my own too!


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## PStechPaul (May 1, 2012)

I have used Microchip PICs for my projects and I made a crude motor controller about 5 years ago using a PIC18F2331. Here are some links to app notes, seminars, source code and schematics for their AC motor control devices and demo boards:

http://ww1.microchip.com/downloads/en/appnotes/00843a.pdf
http://techtrain.microchip.com/webseminars/ArchivedDetail.aspx?Active=42
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en023136
http://ww1.microchip.com/downloads/en/AppNotes/01162A.pdf
http://www.microchip.com/stellent/groups/SiteComm_sg/documents/DeviceDoc/en542813.pdf
http://www.microchip.com/pagehandler/en-us/technology/motorcontrol/motortypes/acim.html

Here is the schematic for Paul and Sabrina's AC motor controller. Might be a good place to start. They use a dsPIC30F4011.
http://www.paulandsabrinasevstuff.com/EVstuff%20info/AC-ControllerPCB%20(Schematic).pdf

And here is an engineering project similar to yours:
http://eet.etec.wwu.edu/ahmanna/project/docs/Prodject description.pdf

I'm thinking about building my own small AC motor controller, integrating it with a DC-DC converter so that the end result will be a system that just needs about 48V of batteries and a standard three-phase motor, and an interface box that will have a set of indicators and controls and USB and/or CANbus or even Ethernet and WiFi connections for remote monitoring and control.

If you are willing to use the Microchip products (preferably the simpler PIC18 devices and not the dsPICs, I'd be happy to help by coordinating our efforts. Not that other processors and platforms are not just as good, or better, but I'm sticking with what I know. My targeted market is for small electric utility vehicles and tractors rather than highway EVs, so a conversion kit would be only about $500 rather than $5000 and up for most cars. But the principles are the same, so the design should be scalable up (and down) to get what is needed with a universal core module. 

I'll look forward to your progress on this project. I really believe AC induction motors have the best combination of attributes for EVs of all sizes. There are others who are designing DIY VF drives with DTC and FOC but I want to make something simple and inexpensive and see if the more sophisticated and complex schemes really are all that much more efficient.


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## Hollie Maea (Dec 9, 2009)

Making an ac controller is essentially a two part problem: you need a power stage which essentially is 6 igbts along with the drivers, snubbers and cooling apparatus that goes along with that. Of course this becomes more complicated the higher your power is, but there seem to be a lot of people on this board who seem to be pretty knowledgable on the subject. The other problem is the controller, which outputs PWM signals to the power stage. This involves algorithm development and microprocessor programming, and seems to be more of a sticking point for many people. You can dramatically simplify this part of the project by using scalar control with no feedback, but this will makes a crummy controller, which may or may not be ok for a school project (it depends on the scope of the project) So I would say first determine the size of the power stage you require, and the type of control algorithm that you would have the ability to build. How familiar are you or others on your team with concepts like feedback control, PID, PWM etc?

Edit: I didn't realize that the OP posted ages ago and is probably long gone. But those are still good things to consider for anyone planning to make a controller from scratch. I am planning to cut my teeth on a 200kw peak ac controller over the next year or two. Unlike most people here I know more of controls than power electronics so I'll be looking for lots of help on the power stage side of things.


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## Arlo (Dec 27, 2009)

Here is a link to my thread on ES http://endless-sphere.com/forums/viewtopic.php?f=30&t=30851 I have it running it is a BLDC controller but all the hardware is basically the same it just different code to run AC induction motors. I am not a code wizard so I have not used this to drive an EV just getting it running on the bench. But All I have left it to write more code and add features as I see fit.


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## joamanya89 (Feb 13, 2012)

Hi, I will answer you on a longer mail in a few hours, but i'll need you to explain me a bit more (kind of translate) of a few things you have said before so I will be able to answer you more presisely, what means or what is "6 igbts" and "snubbers".

Sorry but is the lenguaje problem...


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## Zak650 (Sep 20, 2008)

aravindzzz said:


> I am an Electrical engineering student. As our final year project we are planning to make an EV. We are aiming to convert an old car into an EV. We got a small car which has things till the gearbox. We wanted to make the controller from scratch... soo any one has any ideas or any links which may help me in making a controller ?? We dont want the manufactured one.... we are aiming at buillding one ourselves....


Hi,
You might consider converting an industrial variable frequency drive to be powered by DC and work for an EV.


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## Hollie Maea (Dec 9, 2009)

joamanya89 said:


> Hi, I will answer you on a longer mail in a few hours, but i'll need you to explain me a bit more (kind of translate) of a few things you have said before so I will be able to answer you more presisely, what means or what is "6 igbts" and "snubbers".
> 
> Sorry but is the lenguaje problem...


No problem. The IGBTs are "Insulated Gate Bipolar Transistors" which act as switches in the power stage. Generally you use six of them for a 3 phase inverter.

A snubber circuit is a circuit to minimize voltage spikes during switching events. Inductors (which is what your motor is) resist changes in current, and this resistance is manifest as voltage spikes. Snubbers use capacitors or diodes to limit these transient spikes.


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## cts_casemod (Aug 23, 2012)

Curious how did this turn out in the end?


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