21-12-2021, 07:36 PM
Hi Adrian, flux density at 1.46 is up near the limit for Unisil (GOSS) material, but acceptable.
I suspect that you can use a 4.44 constant (sine)rather than 4.0 (square) in the equation. I think these factors were related to the form factor of the waveform (SQ=1, Sine =1.11), but other specialists may differ. (I can't presently lay my hands on a decent maths textbook that gives all the sine wave factors)
If single ended you will need to gap the core, which will prevent saturation but reduce inductance. It can be calculated but a general rule of thumb would be to use a piece of 0.2mm tape. If you can go for PP so much the better.
The usual guide line for wire size is to run at 3A mm^2 of RMS current (you can simply directly add 1/2 RMS to the DC level. Departing from these figures is no great problem it will simply get more or less hot (with an associated resistance change)
If the impedance is a good bit greater than the resistance this should not be a problem. I do remember a 50's TV set that had an NTC buried in the scan coils to compensate for the tempco of the copper.
Trial and error is I'm afraid your friend as the guys who designed these and knew all the trick are , unfortunately long gone. There may be some stuff in Electronic Engineering from the 40's. The other sources are likely to be the RCA or Philips Tech libraries, which will possibly be in the Pocnet site
Good luck, Ed
I suspect that you can use a 4.44 constant (sine)rather than 4.0 (square) in the equation. I think these factors were related to the form factor of the waveform (SQ=1, Sine =1.11), but other specialists may differ. (I can't presently lay my hands on a decent maths textbook that gives all the sine wave factors)
If single ended you will need to gap the core, which will prevent saturation but reduce inductance. It can be calculated but a general rule of thumb would be to use a piece of 0.2mm tape. If you can go for PP so much the better.
The usual guide line for wire size is to run at 3A mm^2 of RMS current (you can simply directly add 1/2 RMS to the DC level. Departing from these figures is no great problem it will simply get more or less hot (with an associated resistance change)
If the impedance is a good bit greater than the resistance this should not be a problem. I do remember a 50's TV set that had an NTC buried in the scan coils to compensate for the tempco of the copper.
Trial and error is I'm afraid your friend as the guys who designed these and knew all the trick are , unfortunately long gone. There may be some stuff in Electronic Engineering from the 40's. The other sources are likely to be the RCA or Philips Tech libraries, which will possibly be in the Pocnet site
Good luck, Ed
