11-12-2021, 05:44 PM
I think on transformer size vs frequency a square-law might be involved?
An LOPT for EHT is a special kind of inverter, so needs to be single ended as it's the switching off of the valve on flyback that generates the voltage pulse. But a straight drive of scan coils, especially for frame, either direct or via a transformer can advantageously be push pull. It only reduces the core problems to being AC, rather than the DC bias on single ended. A given pair of valves in class B rather than a single valve can give nearly four times the power.
However AC only, nor push pull solve the core issues. Really it's the magnetic field, thus current in the deflection coil that counts. In that case a transformer is a current ratio transformer, but the voltage ratio is the inverse of the current ratio. So 10:1 voltage step-down is 1:10 current step up.
The core saturation is related to turns per volt on the primary and the inverse square of the frequency as the core (even with AC only) can saturate with NO load at all with insufficient turns or too low a frequency. Hence a 220V marginal transformer on 240V can heat up with no load, that can be solved easily. A marginal 110V transformer for 60Hz may have a problem with 110V at 50 Hz, but that has no simple solution, except maybe to try 90 to 100V.
Even in 1980s some very lower power isolated industrial cards were using as high as 1 MHz so as to use a high profile quad DIL 2KV isolation transformer. One core was power and CPU clock, the other 3 were shift clock, data in and data out. 4 x 1N4148 as the "power rectifiers" as the CMOS CPU at 1MHz system clock was very low power.
Subwoofer or woofer filters may use very large air core coils as laminate cores would be very large anyway and add some distortion.
An LOPT for EHT is a special kind of inverter, so needs to be single ended as it's the switching off of the valve on flyback that generates the voltage pulse. But a straight drive of scan coils, especially for frame, either direct or via a transformer can advantageously be push pull. It only reduces the core problems to being AC, rather than the DC bias on single ended. A given pair of valves in class B rather than a single valve can give nearly four times the power.
However AC only, nor push pull solve the core issues. Really it's the magnetic field, thus current in the deflection coil that counts. In that case a transformer is a current ratio transformer, but the voltage ratio is the inverse of the current ratio. So 10:1 voltage step-down is 1:10 current step up.
The core saturation is related to turns per volt on the primary and the inverse square of the frequency as the core (even with AC only) can saturate with NO load at all with insufficient turns or too low a frequency. Hence a 220V marginal transformer on 240V can heat up with no load, that can be solved easily. A marginal 110V transformer for 60Hz may have a problem with 110V at 50 Hz, but that has no simple solution, except maybe to try 90 to 100V.
Even in 1980s some very lower power isolated industrial cards were using as high as 1 MHz so as to use a high profile quad DIL 2KV isolation transformer. One core was power and CPU clock, the other 3 were shift clock, data in and data out. 4 x 1N4148 as the "power rectifiers" as the CMOS CPU at 1MHz system clock was very low power.
Subwoofer or woofer filters may use very large air core coils as laminate cores would be very large anyway and add some distortion.
