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# Television flyback... can be fed with 60 Hz ?

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#### Externet

Hello.
A high voltage transformer to feed the CRT anode uses typically ~15 KHz derived from horizontal circuits -I think-
Can its primary winding be fed instead by 60 Hz at whatever be a proper voltage it may need in order to provide a decent 10KVDC ?
It is not to use displaying video raster nor image, just to emit the beam.

Certainly not. Needs asymmetrical 15 kHz square wave.

Hi,

15kHz --> 60Hz is about a factor of 250.

Thus you need to reduce the voltages also by a factor of 250. --> no chance to get 10kV.

Klaus

I believe the flyback xfmr uses the horizontal raster
sawtooth, not a square wave?

You can feed it at a 60Hz rep rate but the magnetizing
volt-seconds of the pulse need to be kept under the
amount that will saturate the core. I'd recommend a
self-oscillating scheme that turns coil current off at a
set current level in the primary, turns on with some kind
of LF oscillator.

Sine wave drive is unlikely to give you the voltage you
want. You need the abrupt turnoff to a high-Z primary
tap, to force the current out the HV winding instead. If
the primary remains low-Z-driven you will not get the
same boost voltage.

If you operate the flyback transformer with lower repetition rate, you'll get respectively lower output power.

If you operate the flyback transformer with lower repetition rate, you'll get respectively lower output power.
Thank you. Do you mean power or voltage ?

What happens if the 60 Hz is fed in series with a 'small' capacitor that will differentiate the waveform into shorter non-sinus pulses ?

You can't produce a short pulse by differentiating a sine voltage. The primary flyback pulse corresponding to the high anode voltage is in the range of 200-300V, 5 us duration.

FBTs are Ferrite Core Transformers and therefore they cannot be used at low frequencies.

Hi
What happens if the 60 Hz is fed in series with a 'small' capacitor that will differentiate the waveform into shorter non-sinus pulses ?
Differentiating a sine will not change frequency, nor does it result in "pulses" at all. No solution.

Additionally a series capacitance will result in compensating coil inductance. --> the current will become higher instead of lower.
--> earlier saturation. The opposite of what you want.

Klaus

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