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Induction Heater Design Question

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LAN_403

Inducktion

Sat Aug 31 2013, 04:25AM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

Alright... I took these two and basically smooshed them together.

Now my question is, the op amp or op amps that come out of pin 2 on the 4046... do they still do the same thing? I know they're integrators, but ...

Why is the mindchallenger one so much more complicated?

And, it WILL be a series resonant tank circuit. Will all of the current/overvoltage detection stuff work? I omitted some things like the LM393's (and all things associated with them) on the uzzors circuit, and used the mindchallenger schematic for it.

Thanks!

uzzors2k

Mon Sept 02 2013, 08:33PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

I recently published a revised version of my driver, which I have tested successfully with a series resonant topology.

I don't recommend my old driver for new designs.

The mindchallenger driver uses an integrator on the phase comparator 1 output, whereas I just opted for a low-pass filter. I've found that tuning the low pass filter will allow you to set the phase difference that the PLL locks at, and as such I haven't seen a need for a more complicated system.

Inducktion

Thu Sept 05 2013, 06:28PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

Alright cool! But, is high permeability a bad thing for the coupling transformer? I got some "W" material cores here, and their perm is 10,000.... and the AL value is 16,700 MH/1000 turns...

which seems a tad much.

Andy

Sun Sept 08 2013, 02:56AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

This might be a dumb question, but what governs the temperature a induction furnace gets upto? Say if you want to melt something around 1700C would it be easy if you could get ideal variables?

Ben Solon

Sun Sept 08 2013, 03:15AM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

Andy wrote ...

This might be a dumb question, but what governs the temperature a induction furnace gets upto? Say if you want to melt something around 1700C would it be easy if you could get ideal variables?

In a nutshell you just have to have the power applied to the workpiece greater than the dissipation of the workpiece. As the dT between the piece and ambiance gets larger, more power is needed to sustain/raise the temp. With iron and steel you donâ€™t need much to raise it to currie, but once you lose hysteresis heating, eddy currents have to heat the piece alone.

Andy

Sun Sept 08 2013, 03:34AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

Having it in a vacuum would help. :), If you were going to melt steel or iron oxide, would adding Al to the pot help, wouldn't it make more eddy currents because of the low resistance?

Ben Solon

Sun Sept 08 2013, 03:41AM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

Andy wrote ...

Having it in a vacuum would help. :), If you were going to melt steel or iron oxide, would adding Al to the pot help, wouldn't it make more eddy currents because of the low resistance?

If you're generating the same current, then I^2V says that the losses in the less conductive material will be higher. sometimes you actually have to pre-heat things like copper and al so that their resistance becomes great enough to begin heating. I've actually used steel crucibles to melt aluminum and zinc because iron heats so well.

Andy

Mon Sept 09 2013, 12:25AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

Would making the induction furnace have a greater u/k constant work better. If I surround the work peice and the driver coils with ferrite will it work better.

Ben Solon

Mon Sept 09 2013, 12:46AM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

Andy wrote ...

Would making the induction furnace have a greater u/k constant work better. If I surround the work peice and the driver coils with ferrite will it work better.

I've though of that before, and based on very crude experimentation, yes. Increasing the coupling definitely helps, but as for concentrating the field with ferrite, I believe so. I used a flyback core as a platform for a bolt once, and it seemed a little hotter based on color. The core was a U with a cross section of the work coil resting in the center of that U.

Andy

Mon Sept 09 2013, 01:00AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

Hi ben123324

If I run this thing off 60 car battery's, all in series for 1amp(or would 10amp be better at least volts) with a 100 turn primary, and a core made of tungsten to give one turn melt FE2O4 in 30mins at 10ms pulses, and a vacuum setup.

Just trying to get my head around this.

I think I can make the coupling at 0.5.

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