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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
jpsmith123 wrote ...
wrote ...
Its not the wire guage that limits the curretn you can push through, the Guass, determines V/T, which is overall Vout, the H (in Oersteads or whatever) determines your current passability.
Huh? You've lost me there...
well the fewer turns you use on the primary and higher current per H on the ferrite, then the higher the power the ferrite will allow to be transferred. There is no part in which the secondary plays in deciding power, other than it must survive the V and I it conducts. I think.
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
I think we're talking apples vs. oranges here.
I was referring to the "as-built power throughput capability"; meaning that, subject to the constraints imposed, the maximum power throughput will be in the range of 4 to 5 kw.
I could've designed it to run the core at a higher drive level, yes, which would require less turns, and thus allow for bigger wire (and more power throughput), but that would've increased the core loss.
But once the output voltage is decided and the secondary wound, now the core volts/turn is fixed, so the maximum power is limited by the I^2*R losses in the windings.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
jpsmith123 wrote ...
I think we're talking apples vs. oranges here.
I was referring to the "as-built power throughput capability"; meaning that, subject to the constraints imposed, the maximum power throughput will be in the range of 4 to 5 kw.
I could've designed it to run the core at a higher drive level, yes, which would require less turns, and thus allow for bigger wire (and more power throughput), but that would've increased the core loss.
But once the output voltage is decided and the secondary wound, now the core volts/turn is fixed, so the maximum power is limited by the I^2*R losses in the windings.
yeah, ok ill put together a full length PDF, when i get the time after this semester, then we can have a full conversation on all this.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
jpsmith123 wrote ...
I think we're talking apples vs. oranges here.
I was referring to the "as-built power throughput capability"; meaning that, subject to the constraints imposed, the maximum power throughput will be in the range of 4 to 5 kw.
I could've designed it to run the core at a higher drive level, yes, which would require less turns, and thus allow for bigger wire (and more power throughput), but that would've increased the core loss.
But once the output voltage is decided and the secondary wound, now the core volts/turn is fixed, so the maximum power is limited by the I^2*R losses in the windings.
I've posted these specs before, but if your cores are similar to these, then 5 kW sounds about right.
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
Here are some data sheets (power loss graphs) for N27, 3C90 and 50ALL ferrites.
Note that the N27 material is by far the most lossy, followed by the 3C90, and then the 50ALL, the least lossy of the three.
So for the same size core running at the same loss, you could have much higher power throughput with the 3C90, or somewhat better yet with the 50ALL material.
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
I'm in the U.S., Ash.
BTW, the approach that I was originally going to take was to put the HV secondary coil and the multiplier together in the same enclosure and encapsulate the whole thing using some kind of silicone potting compound. (I want the multiplier to be repairable).
What stopped me there was the unexpectedly high cost of the RTV and the fact that all the products I found that I liked, e.g., Momentive RTV12, seem to only be available in gallon sizes (and larger).
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
jpsmith123 wrote ...
.BTW, the approach that I was originally going to take was to put the HV secondary coil and the multiplier together in the same enclosure and encapsulate the whole thing using some kind of silicone potting compound. (I want the multiplier to be repairable).
I won't be potting anything, at least not to start with, for the following reasons:
First, modifying or repairing anything after it's been potted, even in silicon, is messy, time consuming, and unlikely to achieve good results.
Secondly, if cooling is required, this will be much better accomplished under oil. (I think)
I had thought of using Radhu's idea of smearing epoxy over the coil while winding, but I've pretty much decided against it now. I feel that vacuum impregnation after winding would give better results (no air bubbles) and, if under oil, wouldn't be permanent and would improve cooling if required.
It looks like, from the data you posted above, my cores will run hotter at the same power level than your's or Patrick's, but I'm planning on running at a lower frequency than Patrick, so heating may not be a big problem for me. If this proves to be the case I may then consider potting using vacuum impregnation, although that probably won't work on a coil that has previously been under oil.
I'm also hoping that capacitance will be less of a problem at lower frequencies (25 kHz), which should mean I can get more windings on the core, thus increasing voltage, and, maybe, only using a doubler rather than a multistage multiplier (less losses, I think). I also wish to use it for AC, which will mean running without a doubler or multiplier.
I'm still working on the coil formers, heatsinks, and the gate drive circuit, so I've still got quite a way to go.
(currently playing around with 1mm thick clear polystyrene CD cases and methyl ethyl ketone (butanone) to construct welded plastic segmented bobbins)
I'll probably post some ideas I'm toying with about ferroresonant GDT's, something which Steve Connor mentioned in passing, as I think this could have some advantages, but I'll save the details for another thread, once I've got a bit further with it.
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Grooved Bobbins For Segmented Windings
