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  #1  
Old 07-29-2014, 10:00 PM
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Default Homebrew AC Controller Build

Just thought I would post a build progress on my AC controller.
I am currently working on fabricating the chill-plate.
Using a CNC machine I built a while back.
The electronics are almost done.
As you can see in the photo the electronics are mounted on a cardboard backer just for the initial tests and to keep anything from shorting while I move things around.
The electronics are from the J Huebner kit. You can see more information about that kit on another thread in here

Open to any suggestions for improvement. Haven't really thought out the entire build so I am fabricating on the fly.
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File Type: jpg 20140722_203926.jpg (2.22 MB, 75 views)

Last edited by generatorlabs; 07-30-2014 at 04:57 PM. Reason: Title was vague
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  #2  
Old 07-30-2014, 11:29 AM
bwjunkie bwjunkie is offline
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Default Re: Homebrew Build

looks cool to me! (is that Donkey Kong in the background?)

Also, what size is the coolant tubing , what type of coolant and how will you be affixing them inside the grooves?
-josh
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  #3  
Old 07-30-2014, 11:58 AM
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Default Re: Homebrew Build

Yes that is Donkey Kong in the background! That was my "I didn't have anything to do last summer" project. That is a full sized MAME cabinet that is running off an old PC and some scrap furniture grade plywood. Got it loaded with all the classic coin op games! Every garage should have one. With all the old PC's I see put to rest at my local dump it saddens me. Re-use and re-purpose is the name of the game. I used another old PC to build the CNC machine I have that cut this chill plate (that was the project of 3 summers past)

My project for this summer is the AC controller

The machined fluid channel is 1/2 by 1/2 inch so I used those brass hose connectors which have an inside diameter of 1/2 inch. Typical 5/8 OD hose should work fine there with some hose clamps. I will probably use glycol fluid in the chill plate. I have access to tons of it at my job. Everyday anti-freeze is just as good. The hose bibs are mounted on the chill plate cap and are mechanically centered over the beginning and end points of the fluid channel when the cap is screwed down with all those 1/4" bolts.
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  #4  
Old 08-03-2014, 02:40 PM
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Default Re: Homebrew Build

So I made a little more progress:

Verified that pulse train is working

Here are the waveforms from the IGBT driver boards.

Note the voltages that are required to trigger large IGBT's

Also note the required dead-time between the phases. It is difficult to see on the first photo but once you zoom in it is apparent on the second photo. I know I am stating the obvious here but I will throw it in just in case someone is new to this. I was that guy at one point right? Low or no dead-time will lead to catastrophic failure.
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File Type: jpg pic_19_1.jpg (64.6 KB, 56 views)
File Type: jpg pic_18_3.jpg (57.0 KB, 42 views)

Last edited by generatorlabs; 08-03-2014 at 02:48 PM.
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  #5  
Old 08-03-2014, 02:46 PM
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Default Re: Homebrew Build

A little more progress:

Machined some construction grade PVC board to make a mount for my driver boards and terminated drivers to the IGBT's.

Waiting on a delivery of copper bus bar and then I can do some higher voltage testing.
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File Type: jpg 20140803_133906.jpg (570.6 KB, 78 views)
File Type: jpg 20140803_133939.jpg (481.0 KB, 57 views)
File Type: jpg 20140803_155614.jpg (1.87 MB, 85 views)
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  #6  
Old 08-06-2014, 10:44 PM
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Default Re: Homebrew Build

Got a little further today.
Ordered some very nice copper bus bar that I drilled & installed.
I haven't really decided how I am going to bring my power cables in so I left them longer than necessary for the time being. Remember, I am designing on-the-fly

So I am not quite courageous enough to go ahead and put massive current across these IGBT's just yet. I still need a massive capacitor network, some snubbers and a mains fuse. But you know I couldn't resist doing a little something. I put a bench supply in the circuit and drove a tiny 3 phase radio controlled helicopter motor. A video snippet of it running can be seen here:

https://drive.google.com/file/d/0B0y...it?usp=sharing

There is still much work to do but this is a promising start.
.
.
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Last edited by generatorlabs; 08-07-2014 at 09:39 AM.
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  #7  
Old 08-07-2014, 04:59 AM
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Default Re: Homebrew Build

i guess that a next-generation design would not have the bolt heads and coolant taps protruding out the bottom--makes it difficult to sit flat while assembling on the bench.
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  #8  
Old 08-07-2014, 09:30 AM
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Default Re: Homebrew Build

I wrestled with the idea of having the coolant outlets machined in the side of the plate but I decided against it for the following:

a) The main plate is only 3/4" thick. If I wanted to put fittings on the edge of the plate I would have to use smaller threaded hose connector. I didn't want the fitting to be a flow restriction. I used 1/2" NPT connectors. The final machined wall thickness on the top and bottom would be too thin for my comfort. I was envisioning a possibility of slight deforming of the thin walls when tapping or screwing the tapered fitting into soft aluminum. The plate cap and chill plate must remain absolutely flat to maintain a positive seal. When the bolts are tightened the chill plate and cap will be absolutely flush with each other, almost appearing as a solid piece. I did not want to see the NPT thread forming a small bulge when driving the fitting in.

b) I could have bought thicker 1" aluminum but the cost rises exponentially as the thickness increases.

So after debating it in my mind I decided I was going to do one of two things. I would put a number of vibration dampening spacers under the unit to afford me space in my final mounting solution (as shown in the attached photos). I was also thinking of just tapping some bolts into the edge of the chill plate and mounting some beefy aluminum L shaped stock.

Anyway you are correct, it is not ideal placement for the hoses but I do not have an infinite budget for this project so it seemed like a good compromise and it in no way effects performance. In the long run it may turn out to be far cooler this way. For the time being I can live with it not sitting flat on my workbench. I am more concerned with function over form. Sometimes that is how it goes when designing on-the-fly
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  #9  
Old 08-07-2014, 10:39 AM
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Default Re: Homebrew Build

Quote:
Originally Posted by generatorlabs View Post
...I still need a massive capacitor network, some snubbers and a mains fuse. But you know I couldn't resist doing a little something. I put a bench supply in the circuit and drove a tiny 3 phase radio controlled helicopter motor....
Be very careful running even miniscule voltage and current levels through the IGBTs without any decoupling (aka "snubber") capacitors mounted on the bus bar. I managed to blow up a 1200V/600A IGBT module while bench testing a gate driver design at a mere 24V because I was too lazy to mount a snubber cap right on the module... That was a $200 mistake.

However, if you do manage to destroy one or more of those CM400DU modules during testing, I just happen to have several boxes of them which I purchased from the Azure Dynamics bankruptcy auction...
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  #10  
Old 08-07-2014, 11:14 AM
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Question Re: Homebrew Build

Quote:
Originally Posted by Tesseract View Post
Be very careful running even miniscule voltage and current levels through the IGBTs without any decoupling (aka "snubber") capacitors mounted on the bus bar. I managed to blow up a 1200V/600A IGBT module while bench testing a gate driver design at a mere 24V because I was too lazy to mount a snubber cap right on the module... That was a $200 mistake.
Wow..thanks for the heads-ups. Amazing that these things can crush 400 amps but could get toasted at 24V with little current.

Last edited by generatorlabs; 08-07-2014 at 11:21 AM.
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