Dear Rik, look to the attachment.

55, Hans-Albecht

Hans-Albrecht Haffa
DK 8 ND
cba

Goeppingen, August 24th

Dear Lowfers,

ist a really pity that today`s experienced professionals in communication 
techniques have no knowledge about materials, components and magnetics. The 
calculus of a transformer on 136 kHz is really the same as on 50 Hz. Having 
several  years of experience in the development of switch-mode power-supplies I 
know that it is not possible to give a short summary, as many figures I just 
know by experience, not by design manuals.
But I try.

- You can choose every ferrite material with a relative permeability urel 
between 40 and 2500. If You have a material with a Permeability betwenn 3000  
and 6000, reduce the magnetization. I never could measure any differences in 
materials like Epcos (Siemens) N27, N47, N67, N87 or Vogt FI324, FI323. Do not 
use Carbonyle iron powder cores neither for transformers nor for coils.

- Choose a magnetization of about 100 mT = 100 Millitesla = 100e-3 Tesla and a 
current density of 2,5.....15 A/mm2.  15 A/mm2 for small cores, smaller than 20 
mm at ist longest side, 2,5 A/mm2 for the big Toroids with 120 mm diameter. You 
are principally free to use more windings with a smaller core (more copper 
losses) or to use a larger core with more iron volume.  The chosen starting 
value of magnetization and current density is not a secret, it is the 
experience You get in a long time as a professional.

- Choose adequate winding copper material, either round wire, copper-stripes or 
HF-Litz wire.

- Look to Curves explaning the skin effect, that means that diameter or 
thickness of the copper is restricted, depending on the frequency used.

- Measure the temperature rise with a thermocouple termometer or Your wet finger at room temperature. If 
it feels just hot, temperature will be about 60 ø C, so from 25ø C room temperature it will be 
35 Kelvin  rise. A cheap add- on Thermometer for a digital multimeter You get from conrad.com in DL for 
about DM 50,--. If Your transformer becomes too hot, check the copper material or lower the 
magnetization. E.g. lowering magnetization is very effective. Check the  maximum temperature of your 
insulation materials, (130øC,  155øC or 180ø C). Self adhesive tape from the stationary 
shop is not an insulation material !!

- a good book for HF-transformers is:
Jerry Sevick, W2FMI "Transmission Line Transformers", American Radio Relay 
League Inc. Newington
- or also: Catalog from Amidon Associates

- For Coils use gapped ferrites. Toroid Cores may be gapped with a Saw for tiles 
(bath-room plastering) in the DIY-market. It is no problem to cut a 10 mm gap into a  
Toroid with 62 mm OD. I have already built up a filter here at home (LOC:  JN48UQ) in 
G”ppingen.

If You mind,
look to the home page of the following manufacturers of ferrites

Kaschke   DL

Siemens/ EPCOS
Philips/ Valvo/ Ferroxcube   all above in DL
(Ferroxcube also USA)
ISKRA in Yugoslavia
Amidon USA (It is not a manufacturer, this is Fair Rite)
Neosid   DL and UK, UK for Power-Ferrites
Stewart US
Fair- Rite US

DK 8 ND
email: [email protected]

IDD:  ++(0)7161 - 87 847



one side


[email protected] schrieb am 23.08.02 16:48:31:

Hello LF group,

I am trying to make a list of toroid core material that is suitable for 136kHz power applications, for impedance transformers and low-pass filters. I would appreciate any information about the material (brand-type), the application (transformer or filter) and the power level it was used/tested.

many thanks in advance,

73, Rik   ON7YD

______________________________________________________________________________

Hans-Albrecht Haffa
DK 8 ND
cba

G”ppingen, August 24th

Dear Lowfers,

ist a really pity that today`s experienced professionals in communication 
techniques have no knowledge about materials, components and magnetics. The 
calculus of a transformer on 136 kHz is really the same as on 50 Hz. Having 
several  years of experience in the development of switch-mode power-supplies I 
know that it is not possible to give a short summary, as many figures I just 
know by experience, not by design manuals.
But I try.

- You can choose every ferrite material with a relative permeability urel 
between 40 and 2500. If You have a material with a Permeability betwenn 3000  
and 6000, reduce the magnetization. I never could measure any differences in 
materials like Epcos (Siemens) N27, N47, N67, N87 or Vogt FI324, FI323. Do not 
use Carbonyle iron powder cores neither for transformers nor for coils.

- Choose a magnetization of about 100 mT = 100 Millitesla = 100e-3 Tesla and a 
current density of 2,5.....15 A/mm2.  15 A/mm2 for small cores, smaller than 20 
mm at ist longest side, 2,5 A/mm2 for the big Toroids with 120 mm diameter. You 
are principally free to use more windings with a smaller core (more copper 
losses) or to use a larger core with more iron volume.  The chosen starting 
value of magnetization and current density is not a secret, it is the 
experience You get in a long time as a professional.

- Choose adequate winding copper material, either round wire, copper-stripes or 
HF-Litz wire.

- Look to Curves explaning the skin effect, that means that diameter or 
thickness of the copper is restricted, depending on the frequency used.

- Measure the temperature rise with a thermocouple termometer or Your wet 
finger at room temperature. If it feels just hot, temperature will be about 60 
ø C, so from 25ø C room temperature it will be 35 Kelvin  rise. A cheap add- on 
Thermometer for a digital multimeter You get from conrad.com in DL for about DM 
50,--. If Your transformer becomes too hot, check the copper material or lower 
the magnetization. E.g. lowering magnetization is very effective. Check the  
maximum temperature of your insulation materials, (130øC,  155øC or 180ø C). 
Self adhesive tape from the stationary shop is not an insulation material !!

- a good book for HF-transformers is:
 Jerry Sevick, W2FMI "Transmission Line Transformers", American Radio Relay 
League Inc. Newington
- or also: Catalog from Amidon Associates

- For Coils use gapped ferrites. Toroid Cores may be gapped with a Saw for 
tiles (bath-room plastering) in the DIY-market. It is no problem to cut a 10 mm 
gap into a  Toroid with 62 mm OD. I have already built up a filter here at home 
(LOC:  JN48UQ) in G”ppingen.

If You mind,
look to the home page of the following manufacturers of ferrites

Kaschke   DL
Keramische Werke Hermsdorf/ Tridelta/ 
Vogt
Siemens/ EPCOS
Philips/ Valvo/ Ferroxcube   all above in DL
(Ferroxcube also USA)
ISKRA in Yugoslavia
Amidon USA (It is not a manufacturer, this is Fair Rite)
Neosid   DL and UK, UK for Power-Ferrites
Stewart US
Fair- Rite US

A good choice may also be toroid cores of amorphous metals from VACUUMSCHMELZE 
in Hanau, DL or from Micrometals US, but usually they have never samples of 
theese wonderful metal glasses for development. 
So far in this night.

55, 
Hans-Albrecht Haffa
DK 8 ND
email: [email protected]

IDD:  ++(0)7161 - 87 847














one side