7000W Furnace Controller Circuit

[canonicalman]

Many of you probably have technical interests besides electronics. In my case, I have been doing a significant amount of metal work lately, including producing castings from aluminum. To melt aluminum requires a melting furnace, and, as these are fairly expensive, I built my own. The basic furnace is uncontrolled other than watching the interior heat up, and trying to estimate the temperature by the color. When I built my furnace I was disappointed by the lack of a proper controller to carefully adjust the temperature. I checked into buying a controller but found the price prohibitive, so I decided to design and build one myself. For you that may also have an interest and knowledge of metal casting, or have some other reason to control significant AC power, I have posted the design on a web site so you too can build a controller.


http://www.geocities.com/dwviel/FurnaceController.html

Enjoy!

 

[Klaus]

Just out of curiosity, what made you decide to heat your furnace by electricity rather than with a burner? 7 Kw must set your electricity power meter disk spinning at a takeoff rate .
I built a propane burner ( also easy - there's plenty of info onthe web) and a furnace that can melt up to 10kg of aluminium. Have not had a chance yet to cast anything other than making ingots from scrap :wink:
Have fun,
Klaus

 

[John Sorensen]

I used to do controls for furnaces and ovens, and I was told that people like electric furnaces when they want special atmospheres. Every now and again someone would put in an electric furnace because the Electric Utility would give them a kickback ("Incentive") but they were always disappointed by the performance, and they cost much, much, MUCH more to build and, I suspect, operate.

j.

 

[canonicalman]

The reason that I built an electric furnace is that I planned to use it for more than just a metal melter. I actually built two of these and used one for burning out investment casting molds. I also used one of these as a furnace to test materials at specific temperatures where highly accurate temperature control and lack of contamination were of great importance. The furnaces each only hold a four pound crucible, so the total power consumed is rather small. I used maybe a dollar or two a day worth of power for my castings and tests.

 

[canonicalman]

What I would really like to know from the folks on this forum, is what do you think of the circuit? and do you have any suggestions to improve it?

 

[Phasor]

It seems over-engineered, for its purpose. I'm sure we could come up with something much simpler, which would suit you. (though I can't do it right now, I'm about to go out..)

 

[stevez]

No criticism of what you have. Just a thought that next steps might be a microcontroller to allow implementation of other strategies such as PI, PID, etc. I have lots of experience with industrial controls - none of it with microcontrollers however I've surfed thru some sites and was left with the impression that others have written the code for these and other control strategies.

Good luck, have fun!!