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Induction brass annealer redux

Are you water cooling the coil (yet)? I haven't yet hooked up the cooling system and, yes, the coil gets very hot playing around with just a few cases. (In contrast, the caps stay cold.)
 
@dskogman I was looking at this on eBay as well as a potentially better cooler for the MOSFETS. We are definitely underutilising our liquid coolant system.

https://www.ebay.com/itm/Copper-Wat...509?_trksid=p2349526.m4383.l4275.c10#viTabs_0

I was playing with a small Peltier cooling block, but have no real info to offer. It transforms heat input to electricity. Could one be used to take board heat and run the fans? Would be a cheap and simple (too simple?) solution.
 
(too simple?
Yes I think so, too simple and from my experience those little things are terribly inefficient. I doubt there's enough surface area on the bottom of the ZVS to mount a big enough Peltier to come close to transferring as much heat as it takes to be effective
 
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We know that a parallel L(inductance) C(apacitance) tank circuit will oscillate at:

f = 1/(2*Pi*SQRT(L*C)) where L is the inductance in Henries and C is the capacitance in Farads

We can add up the capacitance on the induction board. For the 20A models it is 6x0.33uF or 1.98uF.

Now what about the inductance of the parallel inductor - the work coil? The inductance of an air core inductor is:

L= (d^2 * n^2)/(18d+40l)

where:

L is inductance in micro Henrys
d is coil diameter in inches
l is coil length in inches
n is number of turns

https://www.daycounter.com/Calculators/Air-Core-Inductor-Calculator.phtml

Very roughly, the work coil described in the first couple of posts of this thread has 7 turns and is about 1.25" in diameter and length. (Feel free to refine this.) Plugging these into the calculator above yields 1.05603uH.

We can estimate, therefore, that the resonant frequency of operation of this design is: 110kHz.


It's interesting to apply this to the challenge many are grappling with: the heat produced by the capacitors on the induction board. We know that as the frequency of the AC current circulating in the LC tank (and this current is really really high >75A) rises, the capacitors will produce more heat.

Wima, a manufacturer of very good film capacitors have some charts in the data sheets for their FKP series. Excerpt attached from a data sheet found while browsing for .22uf caps

View attachment 1065359

You can see how as you go up in frequency a lower Vrms sinusoidal waveform causes the same 10 degree rise in temperature.

So, given an existing amount of capacitance on the induction board, what things might make the frequency of resonance higher? A lower level of inductance in the work coil. A great way to do this is to try to avoid shorting a turn in the coil by adding gaps between each 'ring'. You lower the inductance, up goes the frequency and up goes the heat generation. Better to use an insulator or enamel the tubing prior to forming.

If you think a lower frequency is just fine - we haven't really figured this out - just add a few more turns to boost the inductance of the coil, lower the frequency of resonance and reduce the heat produced by the caps.

I believe BillK55 found that the Annie is operating at a much lower frequency. Judging from the pics the EZ-Anneal almost certainly is. It would make sense to understand whether this is important.
 
And while we're on the subject of annealer operating frequency, I just got a reply back from my request of E_Z Anneal on the operating frequency of their unit.

Thanks for the message and yes we do not publish things like that because 1), they are proprietary, and 2), most people don't ask anyways.
However in this case, I will answer your question... The frequency is 110 kHz @ 600 Watts.


I hope Robert doesn't follow this thread.
 
Thoughts about active heating from coil still going on as cartridge drops at end of timer's anneal step. 0.75 seconds is significant relative to overall anneal time with some of the builds where cartridges are running in the 3.0 sec range.

Back on pg 59 of this thread SGK was reviewing his analysis of the coil with his oscilloscope during the anneal step, and he pointed out that it took about 0.75 secs for the coil to decay, and for pretty much that whole time it was at significant power level.

http://forum.accurateshooter.com/attachments/newfile13-png.1065140/

At the time he mentioned it, I didn't really think through the implication of that, but its now sunk in. What that means is as the cartridge is dropping, and moving away from the coil, its still being heated. Furthermore its the tip of the case that's getting most affected, that part that was probably already the hottest.

I don't think its practical to try and stop this from happening, but from a process control point of view (best consistency in annealing) should we give it any consideration?

I feel like its probably a detriment to do something that tends to overheat the tip of the cartridge, so on the flip side should we proactively do something that minimizes that. Has anyone applied any higher temperature Tempilaq (higher than 750) to the tip of the case in order to try and determine how much hotter the tip of the case gets than say the neck? It may be this isn't significant.

I'm waiting on my PS and ZVS to arrive, but I've been playing with my PTR4 timer and seeing how I can work in responses to any problems that might happen like a cartridge not falling into place on the shelf, or the cartridge feeder running empty. I've seen the PTR4 in some other builds and its really quite versatile, much more capability that just a sequential timer. Its limited to 4 inputs, and 4 outputs, so it can never match the ability of the other full service microprocessors other people are using like Arduino, but its a nice in between. Ooops … sorry for the tangent.

Anyways I happen to think about that 0.75 coil decay time and realized with the PTR4 its easy to just add a 0.75 sec pause after the anneal step, and before the cartridge drop solenoid is activated, so that the cartridge is stationary rather than falling as the coil decays. I think that would increase the cartridge to cartridge consistency, as well as eliminate the chance we're doing something to overheat the tip.

Anyones' thoughts are welcome
 
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If anyone is interested in more about the PTR4, there is currently a US ebay seller that's selling it cheaper than the Hong Kong and Chinese sellers, around $20 from seller "newmango" vs around $30 normally. Guessing maybe he bought a large quantity. I've been playing with it quite a bit and haven't had any issues.

https://www.ebay.com/itm/DC-6-40V-L...TR4-Controller-Delay-Module-M2G6/142718754994

As happens frequently with buying ebay documentation can be sub par. I kept googling and finding essentially the same pdf document, and they all referred to an example at the end that wasn't there. I finally found it as a Word document, and saw that the image/table formatting had gotten messed up, and that was why you couldn't see the example. After I fixed the example, I found other format issues causing visibility problems that after correction made the instructions much more clear.

As I said before its much more than 4 timers running in sequence. It has addressable steps like a PLC and can do loops. The 4 available NO/NC 10A outputs can be programmed to operate in any step. The four inputs allow multiple kinds of input signals. Two of the four available inputs can be used to make conditional stops, starts, or jumps. One input is dedicated to starting, and one to stopping.

Even if you don't use it for your annealer, it might come in handy in the future. It even has an additional low level output that can be used to link to another PTR4 and act as the second unit's Start signal.

The only thing I don't like about the PTR4 is the way the terminal connections are positioned. If you were using high voltage level through the outputs, in order to keep from having them exposed you'd want to mount it from behind the panel (to cover the exposed terminals). Doing that makes it a little harder to access the 4 programming buttons. If you're all low voltage you can surface mount it and then you can reach the buttons easily. Somebody better than me could fabricate some button extensions so you could mount it behind the panel, and it would look nicer with the wires hidden.
 

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I have been using the PTR4 controller on my auto feed annealer for more than 2,500 case now, and it has preformed faultlessly. Some more detail in my posts on page 51 and 53. Video on 51 showing it in action.

The main reason I chose the PTR4 was its' ability to be initiated by an external trigger signal. That signal comes from my proximity sensor on the feed funnel as the case drops thru from the auto feeder.

Like you BillK55 I had a lot of difficulty locating sufficiently detailed instructions, but managed to find the same set as you have posted. It is a very simple and straighforward timer / controller once you get used to using it. But I would like bigger buttons for my man-fingers.
 
Mostly corrosion resistance but I can flare the ends and put fittings on to remote locate the coil away from the board but you are correct, I can use copper and flare them also
Perhaps? Keep stray inductance field away from the board. Those two good sized chokes on the board are after all inductors also...
 
Those two good sized chokes on the board are after all inductors also

I already got schooled for saying that. Yes technically they're inductors, but on that board they're functioning as filters to keep the high frequency (generated by the ZVS) from going back into your main power supply. They're not part of the oscillator circuit. And besides I'm not following how switching from copper tubing to stainless changes affect of induction from the coil to the ZVS board.

And I agree with Gina, stainless is going to be harder to work with, and not worth the extra effort since I don't think anyone has experienced any significant corrosion. Most people who recirculate are using a commercial coolant and those have corrosion inhibitors in them.
 
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