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Chris Cristini

Tue Jan 26 2016, 05:58AM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Hi its been a while but i have a project at work I would like to share It is a ZVS Induction heat treat machine for Injection molding ejector pins I am using a HV Transformer for testing and have been abusing the heck out of it but with only 12V@29A about 350W i am waiting for a 1000W 48V SMPS it should be here in a few days from Mouser. I am using a pair of

STE88N65M5.

ProtoTrak CNC machine used.

Video. Back to top

Chris Cristini

Tue Jan 26 2016, 06:20PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Can this be moved to projects I feel its related but it is a project.

Moderator edit: Thread moved. Have fun!

- Kizmo

Chris Cristini

Wed Jan 27 2016, 02:14AM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

First actual test nothing gets hot besides the work coil and the secondary because it is a lossy design how ever can't wait for the big PSU to come.

My transformer is 3 Ecores sandwiched together by nice aluminum brackets I found the idea of the design from a Miller welder and it works OK I used litz wire for both Primary and secondary I am actually considering copper foil but not sure if it will perform better than the beefy secondary.

I am surprised that 12V 350W heats such large gauge wire but losses are a strange thing sometimes. however the PSU is industrial it may be letting more than rated to pass through it shuts off in short circuit conditions so that is good,

Also I forgot to ask in my first post Since the FETs are so large should gate drive be powered by 24V VS 12V? Not actually sure they are turning ON fully.

]img_20160126_205048_890.jpg[/file]
]img_20160126_204706_239.jpg[/file]
]img_20160126_204722_752.jpg[/file]

Chris Cristini

Thu Jan 28 2016, 05:09PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Sorry for all of these posts in a row. hoping for that PSU today we will see. I am getting good practice with the CNC machine.

Of course some of it is Ugly but I am test fitting everything before I get in to finishing touches after this is done i will start building the small stand with a Ball screw actuator for the work piece I am planning on building a cover that seals the work piece in an inert gas environment just for case hardening.

Also when the work piece reaches the curie point I remove some Capacitors raising the frequency and the part actually rises in temperature now my knowledge with heat treating is nominal at best should I stay below or above the curie point?

1454000299 1749 FT175090 1934441 10204209343033381 1515139360552901173 N

1454000299 1749 FT175090 12240047 10204209342753374 378528409132493301 N

1454000299 1749 FT175090 12592183 10204209342873377 8362424256304681382 N

1454000299 1749 FT175090 12592195 10204209343833401 6276136489382391399 N

1454000299 1749 FT175090 12642569 10204209343553394 8690985343795482239 N

1454000299 1749 FT175090 12642605 10204209343393390 691043382494105560 N

1454000299 1749 FT175090 12647521 10204209343233386 7746288830961367922 N

Kizmo

Thu Jan 28 2016, 05:16PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

This looks so nice! As machinist stuff like this really warms my mind

Chris Cristini

Thu Jan 28 2016, 06:15PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Kizmo wrote ...

This looks so nice! As machinist stuff like this really warms my mind

Thank you so much!! You have no idea how much that means to me aside from the 2 axis CNC plasma table I built in 2010 I have very little experience programming but it's my job now :)

update I received the big smps and it worked great however a 1/4" pin glowed red in seconds at 23.6 KHz but then the litz wire primary smoked then shorted what should I use that will handle a kilowatt?

I was also curious of how large of an arc I could draw it was a good one but a few sparks jumped from the source to gate I was sure I cooked a $30 FET but it was unharmed I would recommend these Mosfets to who ever wants to make a ZVS with Isotops cant go wrong with .029 Ohms better than IRF250.

A video of the terminals I used glowing red

More pictures

Inducktion

Fri Jan 29 2016, 08:12AM

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

Well! The terminals are almost certainly glowing red from poor connectivity (look how little of the connector was actually touching your work coil). Because of that you get ridiculous resistive losses, and a lot of heat.

Additionally, if your frequency is indeed 23.6 kHz, then you don't really need litz wire. The skin effect is nil at that frequency and you'll get much much much better results with thicker regular wire.

A quick reading of the datasheet for that fet... 8.8 nF of gate capacitance! That definitely isn't a small FET. You may get better results if you lower the gate /resistance/ a little, since it'll allow more current to flow to the gate. Not a whole lot lower, just a little, like 330 ohms or something.

Chris Cristini

Fri Jan 29 2016, 02:41PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Yea I always seem to overlook small obvious things :) I actually thought the glowing connector was kind of cool but not the purpose I rewound the transformer with normal 4GA and certainly works far better and allows for even more current 5+5 Pri 5 Sec.

Thank you Inducktion I am considering maybe paralleling two 470s for 235 but may be too low ill see.

The company I work for likes everything over built I think I am fulfilling there wish with this another thing is it is nice that I am automation maintenance so have nothing to really do when I keep everything running so nicely and nothing is down.

Wolfram

Fri Jan 29 2016, 03:05PM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Inducktion wrote ...

Additionally, if your frequency is indeed 23.6 kHz, then you don't really need litz wire. The skin effect is nil at that frequency and you'll get much much much better results with thicker regular wire.

This is not true. The skin effect is present at all frequencies, and at 23.5 kHz the skin depth in copper is less than 1.5 mm. With 4 AWG wire, there is already a significant difference between the AC and DC resistance. This applies for a straight wire, in a transformer it will be significantly worse due to the proximity effect, so litz wire makes sense. As long as you have some of proper cross section of course.

Chris Cristini

Fri Jan 29 2016, 07:25PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

I am considering a new transformer design about Half the size as the one I am using and thinking of a water cooled Secondary?

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