Resurrection of a CFEI 100 KVA Induction Furnace

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russ57:
are you sure the electrons can go down the wire in the wrong direction? :lol:

hermetic:
I would leave the jig on whilst you get the cable into place, if thats possible. I once had to attend one in the middle of a field, and wondered how I would find it, don't you worry bout that said Mr farmer, you just stand there and watch yonder, and toddled off to switch on the power in his deep litter hut, After a few moments, a little column of steam could be seen rising from the ground, and it was promptly dug up, to find that the cable had not been laying flat on the bottom of the trench when the joint was made, and as a result the joint had cracked across the resin, I was able to cut 6" off both cables and still have enough to remake the joint. It has given no further trouble, but I must admit those jointing kits are not my idea of fun! This one was the type which used four little line tap type connectors with plastic boots to cover them.
Phil

awemawson:
Well Phil great minds seldom differ - that's EXACTLY what I did !

Oh - Boy what a day - lots done but long and intensive.

While I was waiting for a friend to help me push the four metres back down the hole I made some careful measurements and cut 2.4 metres off the 10 metre flexible conductor, and fitted a further 125 amp fitting to convert it into the 'short umbilical'.

Then my friend turned up, and just as Phil suggested I kept the cable jig on the cable until the last minute as we pushed, pulled and cajoled the cable back down that hole. Once this was done I cleated either side of the resin joint fixing it firmly to the wall inside the foundry. Then I was able to pull the excess cable into the stable and cleat it to the wall at a height that hopefully will stop it being knocked ready for the end wall mounted 125 amp plug to be fitted

awemawson:
Then it was a case of making off the SWA into the male wall mounting 125 amp plug. Having had a problem at the other end I had this time plasma cut some large spanners ready to fit the gland.

Opening up the plug it was revealed that there was no way to make off an SWA gland in it's 'bulkhead' and have enough free cable movement to pull the actual plug unit out to access the cable fixing screws - the whole thing slides into a shroud about 50 mm deep that completely obstructs the cable screws :bang:

The only solution the we could come up with was to saw the bulkhead horizontally through the 32 mm gland entry hole and remove temporarily that bit of the fitting. Then the cable and gland could go deeper in giving room to get the cable ends into their sockets AND fix their screws - the the gland and cable could be pulled back 50 mm and the gland seated in it's now halved hole, and the other 'half of the hole' re-assembled before the gland nut was tightened onto the banjo earth fitting and bulkhead. All rather fiddly and essential to get the cable length EXACT or it wouldn't fit. This took three assembly / disassembly sequences before it was right.

Eventually the cover could be re-fitted and that fortunately also serves to clamp the two halves of the bulkhead back together. Time to screw it to the wall . . .

. . . . arg . . . Houston we have a problem . . I'd assembled it 180 degrees out in the casing. The socket that mates with this plug has a spring loaded lid that needs to be away from the wall or otherwise there is no room for it. Not just a case of rotating in the housing as no way would this cable rotate 180 degrees in less then a few metres :bang:

Fortunately a friend pointed out that as the plug / socket will effectively be permanently mated the lid is redundant - take it off. So I did :clap:

At this point we did an electrical leakage tests at 1000 volt and continuity check - all good :thumbup:

Time to make up the longer umbilical cable. This used the rest of the 10 metre flexible cable so 7.6 metres - I opened up and checked the already attached plug, cleaning up a bit of corrosion, and fitted a free socket to the other end. This umbilical runs from the wall plug up along the RSJ structure of the stable and down to the socket on the generator.

Gosh - fixed wiring FINISHED :ddb: :ddb: :ddb:

Time was getting on and domestic pressures were mounting, but I did manage a very brief test - again getting a bar glowing in the crucible. I ran everything up to about 60 KW and nothing went bang or got hot apart from the contents of the crucible.

More testing tomorrow :zap:

I have managed to source a large three phase RCD unit that has selectable over current tripping (125 to 160 amps) and selectable leakage current tripping (30 mA to several amps) so I will be fitting that to the generator for peace of mind when it arrives, and I also want to improve the earth bonding of the generator, the Furnace Driver, the new Chiller Unit and the particular Furnace Body that's in use. I'm intending to also earth bond the steel structure of the foundry building to these units and the steel structure of the workshop.

awemawson:
Today was largely taken up with other domestic matters, but a run of surface drains that had become clogged with pea shingle afforded an opportunity to use the recovered gravel back filling the cable trench.

This is overkill, 'as dug' back fill would be perfectly adequate so long as sharp stones are removed, but as it was there the cable got bedded in the shingle, then a few inches of earth followed by a row of roof tiles (anti spade penetration!) more earth, then a warning tape before fully back filling to surface level with more earth.

No doubt it will settle, and the far end by the stable is still 'open' as there are water modifications to do before closing the trench. When that's done it can all be re-seeded, and a bit of normality regained!

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