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High Voltage Planar Ferrite transformers. ( Intial Experiments )

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Patrick

Thu Sept 18 2014, 07:23AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

previous purchase

spec sheet, note the "50 all" type saturates at 5,000 guass.

I'll post some math in the morning, but 0.7 x 5,000 = 3,500 guass

TSC 50 all

Patrick

Fri Sept 19 2014, 07:27AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Im needing others to review my math:

possible MOSFET

Im operating with +100 Volts through one primary of 1.5 turns, then -100 volts through the other 1.5 turns. the primary is 3 total turns CT is positive.

so im not sure if the 1.5 turns is multiplied or divided ?

EDIT: the more i think (but am not sure) if the core supports 100v per turn then the 1.5 x 100 = 150 V input. so ill put 150 V in positive then 150 V in negative. I think.

So for the secondary, if its 200 turns x 100 V per Turns = 20,000v.
Which means:
-100v in = -20kv.
+100v in = +20kv.

I do have questions about "low-turn-count" primaries. can a 1/2 tun be used? or do they have to be integers?

this is tempting, but seems like a coupling mess.

This is what i imagined a 1/2 turn primary to look like.

I have no idea how these "balance windings" should be wuond, they obviously cant be a short circuit. I think they must carry current to oppose the different volt potential?

Tony Matt

Fri Sept 19 2014, 11:44PM

Registered Member #3700 Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107

Hi Patric,

Here a summary of the equations that allows you calculate the Bmax in any core .

Regards

1411170228 3700 FT165654 Transt Reactors Jpg

Patrick

Sat Sept 20 2014, 12:01AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

But do i calculate +Bmax then -Bmax as the transformer has a center tap which swings 2 times Bsat...
so i think this is why there is a 2 in the denominator times the turns 'N'...

Hazmatt_(The Underdog)

Sat Sept 20 2014, 03:06PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

100V per turn, is that reasonable?

How long is one turn, maybe 12", and you're wanting to see 100V across that? Maybe...Maybe open circuit operation would give you that kind of voltage output, but I don't think you're going to be anywhere near that in operation.

I'm designing a small transformer for a B+ application, and its more like 1V per turn loaded, probably close to 1.5V per turn unloaded.

10V per turn is probably more realistic, but I can't wait to see how it turns out, I hope it works!

Patrick

Sat Sept 20 2014, 04:00PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Hazmatt_(The Underdog) wrote ...

100V per turn, is that reasonable?

the whole point is to try to get super high volts-per-turn, to avoid high turns on the secondary. If its even possible. for + and - 7kV, 14kV rms, that would mean 70t x 100, which is more wind-able for our purposes.

the more i think the more i believe its a 150 V input. for a 1.5 primary turn. then the flux density makes more sense.

Ash Small

Sat Sept 20 2014, 09:19PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

103 VPT @ 100kHz sounds a bit high for ~5cm^2 ferrite to me but I'm only going on what I worked out for 18cm^2 ferrite @~30VPT @25kHz.

Do you have the formula that relates VPT to frequency?

Patrick

Sat Sept 20 2014, 11:45PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Ash Small wrote ...

Do you have the formula that relates VPT to frequency?

do you mean a function that plots VPT vs Freq?

Ash Small

Sun Sept 21 2014, 12:09AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Patrick wrote ...

Ash Small wrote ...

Do you have the formula that relates VPT to frequency?

do you mean a function that plots VPT vs Freq?

Yep. I assume it may be linear, but it's always best to check. It's a 'volt second' thing, isn't it?

Patrick

Sun Sept 21 2014, 01:10AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

yep my calc says its a linear function, and i see no exponents.

further, maybe i need a single pulse generating 555 timer which drives the power mosfet. then a secondary connected to a o-scope, suitably divieded.

i dont know if a 555 IC can drive a large gate mosfet and still generate a square pulse...

EDIT: i feel like im forgetting something.

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