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Diy Vfd For Automotive Applications


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#1 stelleg151

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Posted 11 January 2007 - 08:21 PM

Hello All,

Great forum you have here; I thought I would post what I am doing to get some feedback.

As the title suggests, I am looking into building my own PWM-based VFD controller to be used for automotive applications; namely a go-kart. (eventually a modified car I hope, but firsts things first)

For now, I have 2 geared fractional HP (90W) 3 phase squirrel cage motors to test with. I also have 6 IGBT's on their way, 6 IGBT Gate Drivers, as well as an 8051 microcontroller for PWM control. The IGBT's will be overkill, but I would prefer to work with IGBT's now so that I can more easily scale up to more powerful motors later.

I wont have these electronics until late February though, as they are being shipped to my parents in Seattle, and I am busy with school in Vancouver. However, I figure I can still get started with an 8051 simulator and schematics.

Here is one site that Ive found that has some helpful information on 6 phase drivers:
DIY 6 Phase Driver

I wont be using this exact drive for a number of reasons, but plan to use some of the principles.

I figure I will post schematics and block diagrams as I go, and any feedback would be greatly appreciated.

Thanks, looking forward to input from you guys.

-George

#2 Carl

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Posted 13 January 2007 - 08:07 AM

Hello George
I also have an inverter project on the burners I’m at the stage of trying to etch the board. I’ve gone for the modular approach.
• The processor(DSP) has dedicated motor control features
• The power stage is a “smart device”

I’ve elicited a lot of information from international rectifiers – unfortunately they are not really interested in supplying a small fish like me.

At this stage I just want to get it put together and then have a lessons learnt review I expect the thing to produce some good smoke signals….but Rome was not build in a day.

If I can make a suggestion – use more than one processor I’ve used one. Two would make for a better engineered product - one for the motor control algorithms and one for connectivity to the outside world. If you are going for something with a safety critical aspect to it then a dedicated processor just checking the circuit is not uncommon (safety through diversity)

Look forward to seeing how you get along.

Good luck


#3 stelleg151

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Posted 24 January 2007 - 06:26 AM

Hey Carl,

Good to hear someone else is crazy enough to fry a few circuits in the search of homemade kinetic beauty.

Ive gotten some schematics for the controller board just about done, and the code is almost done as well.

I've got a cart that I've been adding to slowly at Newark and so far by far the most expensive thing is the anti-parallel diodes. Is this the same for you?

Anyways, the project is coming along fine. I hope the same is true for you.

-George

#4 stelleg151

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Posted 24 January 2007 - 06:58 AM

Oh yeah, and as for the number of processors, I agree that 2-3 would be a more flexible and robust system, but for financial and temporal reasons I will keep this one simple with one processor.

#5 Carl

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Posted 24 January 2007 - 12:38 PM

Hello George

The most expensive part is the smart H bridge which is basically the final stage with all the driver circuits fly back diodes and some other clever short circuit circuitry. I also noticed that I’m driving the surge relay from a 25mA source so need to redo that part of the circuit. Going to use a Space vector control modulation…..unfortunately my maths has gone to pot so its out with all my old books got to the point of trying to decipher the Clarks and Parks but slowly getting there.


Regards
Carl





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