Re: LF: Valve LF amps and tank coil size / voltage rating?

[Andy Talbot <andy.g4jnt@gmail.com>]

That 58mm diameter toroid will have a core cross section in the region of perhaps  300mm^2  (about 17mm square).

2000V DC supply if it is being used as a transformer, means something like 1400V RMS maximum across the winding .

SO at 137kHz, keeping B to 0.1T, that means 

1400 = 4.44.137k.N.300E-6..1,   so Nmin = 76 turns.    Double this for push-pull across  the drains.

If your ferrite core (with a an air gap) is being used as part of  a tank resonator, then multiply the voltage across it , and hence the turns, the by the loaded Q;  in which case it all gets very silly indeed.

Andy  G4JNT

On 14 November 2015 at 19:54, Szigy <yo2is@wa7v.ampr.org> wrote:

the feritte core with 58mm OD, material 3C85.
Inspired by this article have built myself a 2xGU13
(813) PA, 2000V x 0.4A, class C, it works ok in LF or MF !
  73 & DX, Szigy.
-----my reply  to-----------------
Date: Sat, 14 Nov 2015 19:06:26 +0000
rom: Chris Wilson <chris@chriswilson.tv>
rganization: Gatesgarth Developments
o: yo2is@wa7v.#sewa.wa.usa.noam
ubject: LF: Valve LF amps and tank coil size / voltage rating?
eply-To: rsgb_lf_group@blacksheep.org
14 November 2015
If you built a decent power valve LF amp what is the realistic voltage
imit to ferrite cored tank circuits? In other words, what plate
oltage / current is the limit for say a ferrite cored toroidal coil
efore you have to move on to an air cored (very large?) tank coil?
nyone have any links to the limiting figures? All the highish power
alved LF amps I can find are commercial and size was probably not an
ssue, but MAYBE they were pre ferrite toroids, I am not sure when
hey came into usage. Thanks.
-

est regards,
Chris  2E0ILY                           mailto:chris@chriswilson.tv