[TheForge] Inverters-Induction heating

[David E. Smucker]

Steve is right to the point about induction heaters and the required 
power -- remember you got to get the heat from somewhere and it is not 
magic.  So think in terms of the current / power you would require if 
welding and you are in the ball park as to what an induction heating unit 
will require.  Large induction units can be used to melt metal for casting 
operations -- they just take a lot of power.  Kane's unit has requirements 
similar to many single phase welders.

Dave Smucker
----- Original Message ----- 
From: "Steven Smith" <sos at alum.mit.edu>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Saturday, May 26, 2007 9:50 PM
Subject: Re: [TheForge] Inverters


> Ben Barrett wrote:
>> Well certain [electric] motors are induction-run.... things like
>> lights, most heaters, etc, are resistive... I'm pretty sure the
>> standard arc welder is resistive.  Induction uses EMF from a coil, and
>> often involves pulsation (some frequency, similar to AC [vs DC]) and
>> sometimes higher voltage as well.
>>
>> I'm very curious about DIY induction forges, esp. after seeing the
>> nice commercial model at my first conference recently.... I hear some
>> rice cookers use induction for their heat, and am wondering about
>> scrapping some broken-down rice cookers, to try to adapt for small
>> metalworks.  Any thoughts or ideas?  I presume I'd have to isolate the
>> heating element, remove surrounding plastic, change/remove the temp
>> sensor, and so forth, only to be able to heat up a very small amount
>> of metal... but very efficient if tuned.
>>
>> If anyone has experience building their own induction forge, please
>> contact me off-list.  This *might* be a topic worthy of the list, in a
>> new thread.
>>
>> But anyway, yeah, resistance loads are the "common" ones that make
>> most sense, the resistance loads are sort of "sinks" for electrons, a
>> simple heating element is a classic example.
>>
>> ciao,
>>
>> ben
> Ben,
>
> What little I know of induction heating--
> It relies on resonance to pump power into the load (i.e. the piece of 
> steel you want hot). Your work piece will have to be a certain size and 
> shape. Something different will require rebuilding your coil. I guarantee 
> you will not make any headway adapting rice cookers. What does a rice 
> cooker burn, a couple of hundred watts? I bet you need to max out a 220 
> outlet to get a piece of steel up to temp in a reasonable time.
>
> Here is a commercial example:
> http://www.blacksmithsdepot.com/
> Scroll down to the bottom of the page and click on the Induction Forge 
> Basic Kit. I would have given you the link, but it is of a silly length. 
> Notice the closely shaped coils. Notice that it consumes 6kW.
>
> If you build switching power supplies to drive such a thing (I've built 
> and tested supplies that size, but not for an induction furnace), please 
> wear goggles while testing.
>
> Steve
>
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