Where Do I?

[stewartthesmith]

thank you, everyone, for your advise and help. Randy, are you in pennsylvania also?

[J Wilson]

Following is Grant's post from Forgemagic:


grant - Sat 29 Apr 2006 19:56:22 #0
induction
Well, Ries pretty well got your interest. Induction heating has been around since the 30's actually. The thing is that the smaller the work the higher the frequency has to be. Big melters and large billet heaters use line frequency of 60 cycle (60Hz if you're under age 50). For heating a 1-1/2 inch billet you need about 3KHz and for 3/4 you need 10KHz (10,000 cycle). The 10KHz 100KW system I had at my old business would heat 3/4 to 1-1/2 very quickly but couldn't get a piece of 1/2 inch bar past Curie (the non-magnetic point). The little unit that I'm importing runs 30Khz - 100Khz. These higher frequencies only generate heat on the surface of the bar, but it conducts to the center very quickly making them practical for a wider range of work.
The unit I intend to offer is 15KW, that’s about 60amps on 240 single phase. At my electric rate of 4.5 cents per kilowatt-hour that could be as much as 65 cents per hour FLAT-OUT! That’s at full output continuous – never happens. As someone mentioned you’re only drawing power when you’re heating steel. In playing with the unit at the conference we were able to heat about 3 inches of a ½ inch square bar to a good forging heat in about 15- 20 seconds and a full welding heat in 25 seconds. ¾ inch bar was only slightly slower. We did heat about 3 inches of a 1-1/2 inch square bar in about two minutes. Standing there watching it that seemed like it took forever.
Some of the advantages we came up with are obvious some not. Instant heat at the flip of a switch – no waiting for heat-up. I particularly like that when I have an idea and want to try something quick. Ability to get extremely intense short heats. As there is no heat given off except by the heated steel, you can have the coil right next to the anvil, reheat your piece without even stepping away from the anvil. As the heat is actually generated within the part there is little heating of the shop (nice in the hot summer). Oh, did I mention quiet? Yes, totally silent. Coils are easily made from ¼ inch copper tube, three or four turns around any mandrel (broom handle?) and you’re set to go. In operation there is as much as 600amps @ 20 volts going thru the coil. This induces something like half a million amps in the part. Reversing polarity up to 100,000 times per second really stirs things up. I think homebuilt was easier in the vacuum tube era. With solid state you start with an inverter then a computerized “chopper” to create the desired frequency and then a very special (for high frequency) water-cooled transformer. All that plus a control system. ‘nuff for now