Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Thu Jan 31 2019, 12:11AMhere are the imgur pics of the newest transformers in my arsenal.
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Thu Jan 31 2019, 01:17AM
Patrick, Thu Jan 31 2019, 01:17AM
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Thu Jan 31 2019, 02:26AM
it has a 0.005" gap in two places not really happy about that.
Patrick, Thu Jan 31 2019, 02:26AM
it has a 0.005" gap in two places not really happy about that.
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Thu Jan 31 2019, 02:31AM
my edit button doesnt work, so bear with me:
the ebay links :
Patrick, Thu Jan 31 2019, 02:31AM
my edit button doesnt work, so bear with me:
the ebay links :
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
ritaismyconscience, Thu Jan 31 2019, 06:26AM
Might want to put it in epoxy
ritaismyconscience, Thu Jan 31 2019, 06:26AM
Might want to put it in epoxy
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Sulaiman, Thu Jan 31 2019, 07:06AM
Last year in May I bought one of these
a fun little module.
I gave the secondary a dip in polyurethane varnish, I don't know if it helped.
The airgaps are easily adjustable by using different thicknesses of shims (paper, plastic etc.)
As supplied the kit makes 5mm arcs easily but gets too hot for my liking within about 10 seconds of continuous use.
For longer run time decrease the thickness of the shims/airgaps.
(this kit uses a one transistor blocking oscillator so core heating is roughly proportional to frequency and smaller airgaps give lower frequencies)
The primary was easy to unwind and re-wind with a primary of my choice.
I think that this is an excellent bit of kit for anyone starting in high voltage experimentation.
Sulaiman, Thu Jan 31 2019, 07:06AM
Last year in May I bought one of these
a fun little module.
I gave the secondary a dip in polyurethane varnish, I don't know if it helped.
The airgaps are easily adjustable by using different thicknesses of shims (paper, plastic etc.)
As supplied the kit makes 5mm arcs easily but gets too hot for my liking within about 10 seconds of continuous use.
For longer run time decrease the thickness of the shims/airgaps.
(this kit uses a one transistor blocking oscillator so core heating is roughly proportional to frequency and smaller airgaps give lower frequencies)
The primary was easy to unwind and re-wind with a primary of my choice.
I think that this is an excellent bit of kit for anyone starting in high voltage experimentation.
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Thu Jan 31 2019, 04:25PM
yes i considered that module too. its the same transformer. do you mean the transformer or the transistor get to hot ?
i was thinking of removing the shims entirely, making it a normal transformer. then vacuum pulling a epoxy or other material.
a single part urethane for wood is interesting but a bet it would start to volatilize when i apply vacuum.
Patrick, Thu Jan 31 2019, 04:25PM
yes i considered that module too. its the same transformer. do you mean the transformer or the transistor get to hot ?
i was thinking of removing the shims entirely, making it a normal transformer. then vacuum pulling a epoxy or other material.
a single part urethane for wood is interesting but a bet it would start to volatilize when i apply vacuum.
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Thu Jan 31 2019, 06:24PM
primary = 25 turns @ 0.015" , 26 awg.
feedback (or reset ?) = 35 turns @ 0.008", 32 awg.
circle side area is 0.057 inches. (0.27 diam)
im wanting to recalculate a primary for 1500 guass. but i got to go to work. i had all this figured out for my planar and UU cores, but need to look at my notes and maybe find the threads here on the forum.
Patrick, Thu Jan 31 2019, 06:24PM
primary = 25 turns @ 0.015" , 26 awg.
feedback (or reset ?) = 35 turns @ 0.008", 32 awg.
circle side area is 0.057 inches. (0.27 diam)
im wanting to recalculate a primary for 1500 guass. but i got to go to work. i had all this figured out for my planar and UU cores, but need to look at my notes and maybe find the threads here on the forum.
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Sat Feb 02 2019, 08:23PM
ok im attempting to rewind them as a "flyback" type (conventional topology, not TV kind) with a diode+reset winding and no core gap. im not sure waht the volt/amps are for 1500 guass given the above info.
Patrick, Sat Feb 02 2019, 08:23PM
ok im attempting to rewind them as a "flyback" type (conventional topology, not TV kind) with a diode+reset winding and no core gap. im not sure waht the volt/amps are for 1500 guass given the above info.
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
hen918, Sat Feb 02 2019, 10:13PM
Reset winding? You need one of those for a forward converter, not a flyback
hen918, Sat Feb 02 2019, 10:13PM
Reset winding? You need one of those for a forward converter, not a flyback
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Sat Feb 02 2019, 10:16PM
whoops your right. i meant single switch forward.
Patrick, Sat Feb 02 2019, 10:16PM
whoops your right. i meant single switch forward.
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
johnf, Sat Feb 02 2019, 10:27PM
PS
And you normally need a gaped core for a flyback
johnf, Sat Feb 02 2019, 10:27PM
PS
And you normally need a gaped core for a flyback
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Sun Feb 03 2019, 05:29AM
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 ?
Patrick, Sun Feb 03 2019, 05:29AM
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 ?
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Sulaiman, Sun Feb 03 2019, 07:44AM
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.
Sulaiman, Sun Feb 03 2019, 07:44AM
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.
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Sun Feb 03 2019, 08:38AM
what method do you suggest ?
Patrick, Sun Feb 03 2019, 08:38AM
what method do you suggest ?
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Sulaiman, Sun Feb 03 2019, 09:29AM
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
Sulaiman, Sun Feb 03 2019, 09:29AM
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
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
Patrick, Sun Feb 03 2019, 05:45PM
i dont need the pulses perfectly square, spikey is fine as long as theres "area under the curve" so to speak in calculus.
i just need this for electrostatic experiments, could two transformers each with there own HV diode be used to energize the same piece of metal ?
Patrick, Sun Feb 03 2019, 05:45PM
i dont need the pulses perfectly square, spikey is fine as long as theres "area under the curve" so to speak in calculus.
i just need this for electrostatic experiments, could two transformers each with there own HV diode be used to energize the same piece of metal ?
Re: Chinese Small 15kV Transformers and the Oscillograms that will Follow.
MRMILSTAR, Fri Mar 01 2019, 05:08AM
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?
MRMILSTAR, Fri Mar 01 2019, 05:08AM
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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