Motorgenerator induction furnace

[BillS]

It seems there is some interest in induction furnaces.

About 8 years ago a friend told me about an induction furnace that was for sale in a used machinery yard. I took some photos of it and thought they may be of interest to members of this forum.

photo 1. shows a side view of the control panel and the two furnace bodies. The one in the background has a permanent crucible and handles are used to pour the metal out. The one in the foreground uses a foot pedal to eject the crucible for pouring.

photo 2. shows the permanent crucible.

photo 3. shows the induction coil used underneath the pop up crucible.

photo 4. shows the access panel opened to reveal the control circuits and wiring underneath the control panel.

photo 5. shows the motorgenerator running on a vertical axis with the rear access panel removed.

photo 6. shows the access panel and brand name. This unit operates at 10 kc and uses an electric motor to drive an alternator which provides the high frequecy ac to melt metals. It has a 20 Kw output.

This is an old unit and is not made any more. Modern induction melters use inverter grade SCR's to generate the high frequency and are a lot more efficient than motorgenerators. This unit requires some skill from the operator to make it work efficiently. The capacitors have to be manually switched over so the power factor can be kept high so it is not wasting power. It is exactly the same when you tune in to a radio station, a radio uses a variable capacitor to reach the resonate frequency. If you are a little off the radio station sounds terrible and will have less volume. With the induction furnace if the wrong capacitor is selected the metal will not reach the required pouring temperature. Modern units can change the frequency so the power factor can be kept high. The reason why this unit uses a higher frequency is because it uses small crucibles. Most medium sized induction melters use 3 kc frequency. I did think about buying this induction furnace but at $2000 asking price was a little steep for me. Another factor was it uses three phase power and getting it connected to my home would cost a lot more than the induction furnace. As the unit was so old it could very hard to get spare parts if it stop working. I did try to make a induction heater from a microwave oven and got it to work but scaling things up and designing control circuits can be extremely difficult. The same can be done with a car alternator, it can reach a frequency of 1.5 kc but has a very limited output. It is far easier to build a propane fired crucible furnace than to build a home made induction furnace.

Bill.

[BillS]

It turns out the photos are too high and too wide, I will have to reduce the photo size.

[rrnut-2]

As far as three phase power is concerned, it is best to power the induction melter power supply with a diesel generate. I know one person that had done that to run his 175Kw Inductotherm. You also need to run cooling water pumps. On most SCR units, that would be two pumps.

Jim B

[BillS]

Here are the photos

[BillS]

photo 6.

[Harold_V]

For those who may have an interest in a second generation induction power supply (motor/generator type), be informed that they contain water cooled capacitors which are most likely filled with PCB's. If the unit has been allowed access to a freezing environment (as mine was), the cost of disposal if they are leaking will be enough to trigger a heart attack (speaking from the position of one who has been there, on two occasions). The cost of replacement capacitors will be equally as expensive (been there, done that). Do your homework before getting involved.

Harold

[rrnut-2]

I will add to what Harold says. If you see a large amount of swelling of the capacitor, be leary. Also, ask the age. If they are older than 20 years, they may have PCB's in them. The foundry that I worked at, we changed all of the caps right around the early '90s.

Jim B