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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
yes but i wont be using these as a flyback. ive removed their gap.
Qustion: what if i leave out the parallel diode, inductor and capacitor which are usually used ?
this is what i want :
the intrinsic diode in the mosfet or igbt worries me though. should i put a diode in series so at turn off the current doesnt try to rush back in the opposite direction through the primary ?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
The inductance of each winding is proportional to turns.squared and inversely proportional to the effective magnetic path length i.e. air gap lengths + (ferrite lengths/relative permeability) so with no air gaps the inductance of the secondary will be very high, when combined with intrinsic plus added external capacitance, the self-resonant frequency of the secondary may be too low for your needs.
As a flyback the maximum energy storage per cycle is proportional to the effective magnetic path length.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
For a train of unipolar 15kV pulses I'd use airgaps and flyback mode, the actual voltage waveforms would depend upon the load, e.g. the equivalent of a 15kV zener diode as a load would produce the required waveshape.
In any case your dv/dt will be limited by secondary current and load capacitance, so a 'square' pulse is impossible. (Isec = Ipri.(Np/Ns) also secondary resistance is about 1kOhm)
For bipolar trains of pulses I'm unsure / not thought about it before, I guess that you would need to use the transformer as a pulse-transformer - very low magnetic flux leakage = minimum air gaps and concentric windings, having the primary and secondary on different segments of ferrite will inevitably lead to leakage flux = leakage inductance and the resonant frequency of the secondary will be important. The primary would need bipolar drive (H-bridge or bipolar power supply or push-pull dual primary)
As a pulse transformer you will need to calculate (v.t/n per pulse)x(number of pulses in a train) vs. saturation
Registered Member #62119
Joined: Sun Feb 04 2018, 04:59AM
Location: Cedar Rapids, Iowa
Posts: 136
I am considering building a Cockroft Walton multiplier for which I need a HV AC source. I could use one of my NSTs but they are heavy and bulky. Could one of these be used? I would remove the primary and make a new primary consisting of 8 turns with a center tap. I would use a ZVS driver to power it. I would use the coil as a flyback with an air gap. Could it be run continuously without over heating? Would I have to pot the secondary coil?
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Chinese Small 15kV Transformers and the Oscillograms that will Follow.
