RE: RE: LF: Iron dust toroids and heating

["Clemens Paul" <cpaul@gmx.net>]

Hi Marco, 

>I don't know if the saturation formula used calculating B on 
>transformers is valid also for inductors

It is indeed.
B =V/ (4.44*F*N*A)

>Beside this, 2kW on 50 ohm should mean rad(2000*50)=316Vrms 
>not 600
> I'm >wrong?

No,but I was referring to V across L2, not across the load.
See the three attached spice simulations.

73
Clemens
DL4RAJ 

>-----Original Message-----
>From: owner-rsgb_lf_group@blacksheep.org 
>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of 
>marcocadeddu@tin.it
>Sent: Friday, May 26, 2017 8:16 PM
>To: rsgb_lf_group@blacksheep.org
>Subject: R: RE: LF: Iron dust toroids and heating
>
>
>Hello Chris, Hello Clemens,
>
>wish to share a couples of mumblings..
>I don't know if the saturation formula used calculating B on 
>transformers is valid also for inductors.. probably we should ask some 
>more addicted guy, there is something that does not make me 
>happy using 
>it from an aestethical point of view but could be wrong ...
>Beside this, 2kW on 50 ohm should mean rad(2000*50)=316Vrms 
>not 600 I'm 
>wrong?
>Unfortunately I will probably cook my FET during the weekend so I have 
>not yet 1 kW for testing.. but Chris let me ask: have you already 
>checked the attenuation curve of your LPF? are you sure the LPF is 
>correctly resonated? or could you excite your PA at lower frequencies 
>and see if the behaviour is still the same?
>
>I had the same problem with a PI LPF it was loading a lot the TX and 
>heating a lot.. I made coils bigger and bigger but no changes.. 
>switching to T type like W1VD design with coils made on T200A-2 (the 
>T225A-2 were not available) solved all problems at power level of 3-
>400W with good attenuation of armonics and very low insertion 
>losses. I 
>agree my power was one fifth.. but a check could be worth ;-)
>
>GL de Marco Ik1HSS
>
>----Messaggio originale----
>Da: cpaul@gmx.net
>Data: 25-mag-2017 14.28
>A: <rsgb_lf_group@blacksheep.org>
>Ogg: RE: LF: Iron dust toroids and heating
>
>Hello Chris,
>
>>> I was wondering if the #3 material which is rated for use 
>>>from 0.05 to  0.5 MHz, and has several times the permeability would 
>be a better
>>> choice for more power through it? 
>
>>Yes that sounds like a good concept.
>
>Look what the mini ring core calculator is showing (see 
>attachment) and 
>draw your conclusions.
>The calculations are completely based on amidon data.
>I've chosen 600V RMS ,that's the voltage drop across L2 at the 2kW 
>level.
>For #3 I had to resort to T200 size because 225 is not available for 
>this material.
>
>73
>Clemens
>DL4RAJ 
>
> 
>
>>-----Original Message-----
>>From: owner-rsgb_lf_group@blacksheep.org 
>>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of DK7FC
>>Sent: Thursday, May 25, 2017 2:09 PM
>>To: rsgb_lf_group@blacksheep.org
>>Subject: Re: LF: Iron dust toroids and heating
>>
>>Hi Chris,
>>
>>Am 25.05.2017 12:40, schrieb Chris Wilson:
>>> I was wondering if the #3 material which is rated for use 
>>from 0.05 to
>>> 0.5 MHz, and has several times the permeability would be a better
>>> choice for more power through it? It probably gives a higher Q with
>>> fewer turns, allowing the use of larger wire without having
>>> overlapping layers in the winding?
>>>    
>>
>>Yes that sounds like a good concept.
>>
>>It is interesting to follow your plans. Actuelly i would like 
>>to try to 
>>build a  2.5 kW or larger PA as well, just for interest of course. I 
>>would of course use it together with a dummy load only, 
>>because you must 
>>not radiate more than 1 W here in DL, and i am a conformist and under 
>>the spell of authorities (german: autoritätshörig) :-)
>>It would be interesting to deal with the problems that would 
>>appear with 
>>such PAs. For say 3 kW and the comfortable situation to have a 
>>suitable 
>>60 V power supply, i would simply build a current mode class D 
>>PA, hard 
>>keyed with an IXDD614CI and 2x 4x IRFP260N FETs. For the LPF i 
>>would use 
>>the T225A-2 together with RF litz wire, maybe 250x0.1mm, available at 
>>https://www.spulen.com/hf-litze-250-x-0-1-mm-100-g-spule.htmland 
>>WIMA-FKP-1 capacitors, the 2 kV version...
>>
>>Good luck and fun with your projects.
>>
>>73, Stefan
>>
>>
>>---
>>Diese E-Mail wurde von AVG auf Viren geprüft.
>>http://www.avg.com
>>
>
>
>
>

Voltage across R.JPG
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Voltage across L2.JPG
Description: JPEG image

Power.JPG
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