Resurrection of a CFEI 100 KVA Induction Furnace

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awemawson:
So let's try and actually MELT some metal :bugeye:

First I carefully scraped out the crucible that is embedded in the inverting 'Furnace Body' and removed some iron slag and very small traces of copper slag. (Remember that I installed this crucible brand new many years ago, so this confirms that in the past I have melted both iron and copper with this beast). It's an awfully long time ago and I've had various furnaces over the years, so what was done in which gets a bit hazy !

Then, as I had no mould prepared, I selected a conventional crucible from my stock that would sit inverted on top of the furnace body, and when clamped and inverted would receive the molten metal - let's call this the 'drop crucible' (and hope we don't !!!!)

A test clamp, invert, release and all seems well so I charged the main crucible with a bit of copper scrap left over from the installation.

awemawson:
So :-

A/ Start the generator and close it's isolator

B/ Turn on water stopcocks from Borehole, which automatically starts the borehole pump

C/ Power up the New Chiller Unit and check for water flow

D/ Turn on the massive main switch on the CFEI and 'Ping' to measure resonant frequency

E/ Check Compressed Air is 'On' to Furnace Body

F/ Change CFEI Keyswitch from 'Test Frequency' to 'Normal'

G/ Wind the power control to minimum and press 'Chauffe' keeping fingers crossed!

H/ Slowly turn the power up to initially 67 KW then 75 KW listening to the generators 'note' getting harsher.

I/ Watch things starting to smoke then glow very hot.

Now I have no recollection of this happening previously, but a light saying 'Limit' comes on around 75 KW and no further increase seems to be allowed - it must be a pre-set parameter but as I say I have no recollection of it. In fact the display tops out at 77 KW.

So, watching the pot, things are getting extremely hot but no apparent melting happening - the long copper pipe had a dribble of molten metal down its side which formed a cut in the tube, but it's not forming a pool in the base of the crucible as I had expected.

I left it running at 77 KW for a while, and went to inspect the generator which was running magnificently but nothing looking untoward - I took a picture of it's control panel showing 150 amps of load but it's come out very fuzzy - either I was shaking or the camera didn't focus!

The chiller unit using the bore hole water seems to be working fine - I think that the maximum return temperature from the furnace was 34 degrees C - it's picture DID come out OK!

So, ramping the power back down I shut everything off and inverted the furnace body to drop the result into the drop crucible.

When it had all cooled I could then examine the results - each pipe section had. like the long one, a melted bit down it's length that had turned the complete circumference into a 'C' shape.

My theory -and PLEASE COMMENT if you have other theories is as follows:

The furnace melt metals by inducing eddy currents into the charge by transformer action, the charge effectively forming a short circuited secondary winding. Here the pipes having broken the circle are no longer carrying the major current that they were.

I think, given a reasonably dense initial charge that will form a pool in the base, and absorb much of the power, further small stuff will melt into the pool quite satisfactorily

Time for more reading and experiments, but I'm being called away on 'other matters' at the moment.

russ57:
Can you start with something dense, as you suggest, but maybe aluminium or even a small coil of copper wire?

-russ

awemawson:
If at first you don't succeed, try, try again :lol:

I've had a lump of what I'd thought was copper at the back of my bench for years - rescued from the scrap of my foundry when I moved all those years ago, so I thought I'd try and melt that - about 5 kg.

Well it was too large for the crucible on the inverting furnace body so I started cutting it in two on the band saw. I wasn't entirely surprised when the blade broke - copper can be gummy, it was over an inch thick and far from stable on the saw table. Never mind, finish it with the Angry Grinder with a 1 mm disk. Now soft copper and disk cutters don't go well together, so why was it cutting so well :scratch: Because it's BRASS :clap: It had only looked coppery as the surface had been de-zincified.

So now it fits in the pot I went through same rigmarole turning everything on, ran it up to 75 KW - took a decent picture this time of the generator panel (!) returned to the foundry and it was already practically melted. Another less than a minute and the zinc was boiling off, time to invert the furnace.

I got a little bit of brass splash as it went over - I was probably a bit too slow doing it - then the furnace driver gave me an error light. (Water pressure or temperature to / from furnace body but not sure which)

Everything turned off, drop crucible released, and a 2.5 kg dome shaped lump of brass was deposited on the floor.

It was at this stage things got a bit hectic as one of the brewers hoses that carry the chilled cables from the driver unit to the furnace body decided to burst and squirt coolant onto the floor.

Now this is not entirely a negative, as it will persuade me to replace them despite the not inconsiderable cost, and it is best for safety anyway.

So this escapade had proved that the furnace is fully working, albeit that I have a few issues to correct.

Quite impressive rate of melting - 2.5 kg of brass in about 5 minutes - actually probably a bit less as I'm taking that timing from time stamps on the photographs.

. . . off now to cost rolls of Brewers Hose :bugeye:

WeldingRod:
I think you will have problems melting Things that are only a few skin depths in one dimension.

I've seen that worm tracking thing back when I tried to build a RF shunt to handle a kilo amp using thin brass sheet. Some kind of field concentrating thing going on that runs away gleefully with positive feedback.

Sent from my SM-G892A using Tapatalk

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