2500 W Induction melting system

Apr 19

This project has a funny background story. I worked a lot with induction melting in the past (alloy development) and in fact I still work with it during my daily job. But of course this 2.5 kW equipment cannot be compared to the 15 kW unit that I use at work. Nevertheless, I faced some obstacles that I could not solve at my workplace and due to the strict (but fair) safety regulations I am not allowed to hack the induction melting equipment. So, out of frustration I started to build my own miniaturized melting equipment that I will use as a proof of concept to show that my idea should/would work.

This system is based on a 2500 W ZVS driver. The ZVS driver is powered by a 3000 W telecommunication DC power supply which is capable of supplying 62 A at 48 V; it is perfect for the driver. This enormous power is switched by a 80 A, water-cooled solid state relay (SSR), and the momentary power consumption and related values are measured and displayed by a power meter that utilizes a “100 A, 75 mV” shunt resistor. The SSR and the induction coil needs cooling, therefore I decided to assemble a water cooling system to serve the demands. The cooling system consists of a 12 V water pump and a radiator that can accommodate three 120 mm fans. The SSR is fixed to a 40 mm X 40 mm water cooling block and I added some thermal paste to increase the thermal conductivity across the contact area. The water cooling system is floating (in terms of electrical connections), since the water is in direct contact with the live induction coil. The power meter is powered by the 48 V power supply, and for the rest of the components (fans, pump, thermometer), I added a 12 V 5 A power supply. As you will see in the schematics, we first need to switch on the cooling in order to be able to switch the SSR and power up the ZVS driver. It works the other way too: if you switch the cooling off while the ZVS is still running, the ZVS is also shut down.

Schematics and additional photos

I used the following parts for this device. If you use these affiliate links, you are supporting my work:

2500 W ZVS driver

3000 W DC power supply

Side view

Here you can see the pump at the top left corner of the frame. Under it that’s the radiator that can accommodate 3x120 mm fans. The fans are on the other side and pushing the air through the radiator. At the front side you can see the thermometer panel, the coil, and a the power meter panel.

Front view

At the top left corner, that’s the k-type thermocouple thermometer. On the right side, that’s the power meter for the ZVS driver. The two switches under it switch the 12 V and the SSR. One cannot switch the SSR on without having the cooling system powered on.

Closeup of the controls

Here you can see the power meter, the two switches for the 12 V and for the SSR, and the front panel of the DC power supply that provides the power for the ZVS driver.

Induction coil

This is the original coil that came with the ZVS driver. Due to its large diameter, it is not the most efficient configuration for heating up things with small diameter such as rods, bolts and similar stuff. For a good coupling, the heated object should have similar diameter as the inner diameter of the coil.

230 V inlet with switch

This is a C20 type inlet socket. I also 3d-printed a plate that allows me to fix the socket at one of the corners of the frame.

The bowels

Here you can see a lot of thick wires (16 mm^2) that deliver the DC power to the ZVS driver and some plumbing that keeps the SSR cool.

12 V water pump

Just a simple pump with a reservoir. You can also see the thermocouple hanging on the frame.

Shunt

This shunt measures the current passing through the ZVS circuit. I 3d-printed a holder for it so I can attach it to any surfaces using four screws or bolts.

Wiring