How-To: 30 kW Induction Heater

Instructables user bwang writes:

This Instructable will walk you through the construction of a high-power (30kVA) heater, suitable for melting aluminum and steel. Note that to take full advantage of this design, you will need a 220V outlet, at least a 50A single-phase one and preferably a 50A or 60A 3-phase outlet.

Obviously, one should read, understand, and be comfortable with the safety procedures before attempting something like this, but what an awesome tool to have.   Using scavenged materials, he estimates the build cost $200. It’s an entry in Instructables ongoing EXTREME! Challenge.

30 kVA Induction Heater

12 thoughts on “How-To: 30 kW Induction Heater

  1. The circuit is very flawed in what comes to the gate drivers. It might work, but most likely you’ll end up blowing your bricks and getting a nice sort circuit. Add fuses if you build that!

  2. As an experienced induction heater designer, I can assure you that the machine is not a 30kW induction heater. Given the small conductor sizes in the tank circuit and the small resonating capacitor, it is likely a 27 or 28kW water heater and a 2-3kW induction heater. My 2.5kW heater can melt a piece of metal the size that he shows in the first photo.

    John

    1. The only way to know for sure is to measure it. Here at Fluxeon, we do it calometrically. There is a length of 2″ galvanized pipe with a cap on each end. The cap is drilled and tapped for a 3/8″NPT straight T. To the straight part of the Tee is connected 1/4″ nylon tubing to bring water in and carry it away. On the arm is epoxied a bare type T thermocouple positioned so that the junction is in the water stream. Downstream of the TC on the outlet side is a pinwheel type flowmeter that generates one pulse per cc of flow. All of that feeds into a custom AVR based board that takes the change in temperature though the dummy load and the flow rate and uses the specific heat of water to compute watts

      You can do it much simpler. Make up a dummy load as I described. Run water through it until the water temperature stabilizes. Turn the heater on and measure the outlet temperature after it stabilizes. Measure the flow rate by measuring how long it takes to fill a measuring cup, a graduated cylinder, gallon paint can or whatever. Then do a little math.

      Let’s say the water was 18 degrees going in and is 50 degrees coming out. It took one minute to fill a gallon (3785.4 cc). Since a cc of water is also a gram of water, it flowed 3785.4 grams of water. The specific heat of water is 1 calorie/gram-degC. The formula is Q=c*m*delta T where Q is calories, c is specific heat m is mass and of course, delta T is the change in temperature.

      So let’s get started. Q = 1*3785*(50-18). That works out to 121,120 calories. There are 4.1868 watt-seconds in a calorie so we get 121,120*4.1868 = 507105.2 watt-seconds.

      It took 60 seconds to fill the gallon can so divide watt-seconds by seconds to get watts. 507105.2/60 = 8,451 watts.

      If you don’t want to do all that by hand, here is a page with a calculator: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html#c2

      Gee, I hope I got all the math right :-)
      John

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I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and makezine.com. My work has also appeared in ReadyMade, c't – Magazin für Computertechnik, and The Wall Street Journal.

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