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