Subject: Re: Induction brazing from old microwave oven?

From: [email-masked] (Kurt Rieder)
Date: 30 Jul 1996 20:32:09 GMT

burt lang ([email-masked]) wrote:
: Induction heating by definition is heating by means of AC current 
: generated when the workpiece becomes the "shorted turn secondary" in a 
: transformer.  The primary of the transformer is powered from low 
: frequency (such as 50 or 60 Hz) AC power.  A microwave oven is totally 
: useless for this application.  A spot welder if it had a high duty cycle 
: might be a possibility.  Feed the power thru a coil of copper tubing with 
: water flowing in the tubing to keep it cool.

Agree that microwave heating of metal is entirely inappropriate.
However 50/60 Hz is also equally inappropriate in the opposite direction.
Induction heat treat and braze equipment that I have seen in use was
typically 3 KHz and higher.  Have used induction melting furnaces that
ranged from 100 lbs @ 3 KHz, 1000 lbs @ 1.2 KHz,  3000 lbs @ 180 Hz,
(The latter by means of a static harmonic trippler from 60 Hz).  It is
not until you get up in the range of 10, 20, tons or more of metal that
you begin to see 50/60 Hz powered melting/holding furnaces.

I would hate to see an enthusiastic person rush ahead and wind up a coil
and burn up his spot welder :-}