The Craftmans Shop > New from Old
Resurrection of a CFEI 100 KVA Induction Furnace
awemawson:
I wasn't over happy using 6 mm poly-carbonate to mount the new contactor - it can flex a bit and can shatter - think door being slammed on the handle mechanism - so I decided to remake the mount in 2 mm zintec steel sheet.
Obviously a job for the CNC plasma cutter - so I drew up the panel in Autocad - ported it to sheet cam - and oops - the PC on my CNC plasma table has died :bang:
Gives very odd power on self test beeps that don't feature in the book of words. So diversion into PC fixing - it's quite embedded physically but I got it out and apart - no obvious problems - re-seated things, blew it out with an airline and it came back to life. Probably moisture - very damp at the moment in the welding shop.
OK steel panel made - this let me tap it 3/16 UNC to mount the new (to me) ABB SACE S3 contactor despite having no nuts !
Then a bit of hefty re-wiring in extremely stiff 35 mm CSA 'tails', followed by re-wiring the trip circuit to use the normally closed contacts on the trip delay unit. . . but no . . not so fast . . .the blooming normally closed contacts aren't working - more moisture problems i think. Well it turns out the the base Estop relay that the delay unit fixes to has an unused normally closed pair of contacts - heck who wants a delay anyway !
So putting my fingers in my ears I put 415 volt 3 phase from a local 16 amp circuit on it as I've done previously and yes everything seems to work as it should. Hit the red button and the contactor trips, power up and the controller goes ready, allows me to 'ping' the crucible coil and then I did a VERY brief 'heat' remember only on a 16 amp circuit at the moment.
I think the only thing left to do is sort out a through door operating handle for the contactor - I've failed to source a genuine ABB SACE S3 one but may be able to machine a converter for the original Socomec one - but that's for tomorrow - been at it all day and I've had enough.
awemawson:
Happily it turns out that adapting the original operating handle from the Socomec contactor to the ABB SACE one proved far easier than I had dared hope :thumbup:
The ABB has a 10 mm square operator bar - the Socomac has a 15 mm square bar, AND the original physical door interlock mechanism (Female slotted arrangement on the door and a nylon unequal rectangle on the contactor) will JUST squeeze into the depth where the new contactor sits allowing not only electrical operation of the trip switch but also mechanical interlocking preventing the door being opened when the switch is 'on')
So by milling part of the 15 mm operating bar down to 10 mm square using a rather flaky clamping set up I was able to re-assemble it all AND it works !
I had envisioned having to create 3D parts and printing them out but hoo-ray not needed and the furnace is now back in commission.
russ57:
Now just need to remember why you needed it working...
awemawson:
Russ - next job is to cast a bit of bronze into a bar for Pete. to turn into an anti-backlash nut for his mill, however external pipework is frozen at the moment !
I had a bit of luck on eBay where an identical 'delay timer module' to the one that I had to remove from the eStop circuit turned up at a very modest price. It's been rather held up in the post, but arrived today and it was rather TOO identical in that it's normally closed contacts were open circuit at all times testing with a Fluke :bang:
However it had obviously been previously only using the 'normally open' contacts in it's former application so the other pair had probably been oxidising gently for the last thirty years. Increasing the wetting voltage to 24 on a lab supply with current limiting almost immediately it started working OK and now is fine. (In my application if this contact is not closed the machine won't connect to mains so any doubt about the contact isn't a safety issue)
These units are not designed to be taken apart otherwise a simple clean with a bit of nice abrasive printer paper between the contacts would have given the same result.
When things are a bit warmer in the foundry I'll fit it!
awemawson:
A Fast Foray -into a Freezing Foundry and I've Fitted the replacement time delay.
First a quick picture for the record of how I'd borrowed a spare normally closed contact pair on the host eStop contactor in case things didn't work out, then a simple job of re-routing the wiring in the panel conduit having clipped on the time delay. Testing it works just as expected so thankfully a 'none event'.
I was a bit puzzled why the designer had incorporated this 300 mSec delay but thinking about it it gives the microprocessor 300 mSec to close down the various drivers etc before power is lost so probably sensible.
. . .so no 'guv we was never there . . it's exactly as it was :lol:
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