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30 kV 10 mA power supply

Discussion in 'Electronic Design' started by booth, Nov 27, 2006.

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  1. booth

    booth Guest

    Hi Again,
    Thanks for all the answers. After searching I've found the high
    voltage switching transformers at 12,000 Volts at 35 ma for
    115V input. I plan to connect 2 of them in series to get the desired
    voltage. I will apply 220V. Has anybody here used them before? Will
    they be suitable for capacitor charging?
  2. I am sorry, but if you connect them in series, the twice higher
    voltage between secondary and primary may exceed their safe insulation

  3. Tom Bruhns

    Tom Bruhns Guest

    Adding to what "Ignoramus" (who seems to not be one) already posted...
    a serious problem when you get to high voltages in transformers is
    corona. If there is corona around organic insulation (which is almost
    always used in transformers), the insulation will eventually break
    down. It may not happen right away, but could instead be a field
    failure built into every unit.

    On the other hand, what's wrong with using a voltage doubler? The
    transformer is rated, apparently, at high enough power for your
    application, so why waste money on two of them? 12kVrms should give
    you over 17kV peak, more than enough to get your 30kV with
    appropriately sized capacitors.

    Be prepared to use corona rings, lots of space, etc., to keep electric
    field strength under control...

  4. Boris Mohar

    Boris Mohar Guest

    At someone lower current this one might do the job. I do not know the seller
    but he has been trying to sell it for a while. Like he says, this thing is
    lethal. When hooked up to sizable cap you will not have the time to smell
    the burning flesh. What is it that you are trying to do?


    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs (among other things)

    void _-void-_ in the obvious place

  5. Thgese are NOT for running off the Ac line, NOR for putting in series.

    The secondary is apparently center tapped, with the center grounded, so
    it's better explained as a 6000-0-6000 volt transformer. NOT something
    that can be used as a 12,000 volt transformer, and definitely not in
    series with another such ilk.

    And you can't drive it form the AC line, as it only has about six turns
    on the primary.
    You have to drive them with what they allude to as their "power
    supply, schematic included".

    Have you ever built a 400 watt switching power supply, from scratch,
    before? Not as easy as you might think.

    I suggest trying something less likely to result in smoke, fire or
    death, like dismantling land mines.

    Do your parents or life-insurance agent know what you're planning?
  6. booth

    booth Guest

    Thanks for your safety concerns. I plan to put the transformer in oil
    anyway.I guess that will solve the insulation problem. I'm aware that I
    cannot use AC directly. There must be some high frequency switching
    involved. The output of the secondary will be rectified. The voltage
    doubler idea seems interesting instead of using 2 transformers in
    series. But how much space will it occupy?

    Tom Bruhns yazdi:
  7. JoeBloe

    JoeBloe Guest

    A voltage doubler is two HV capacitors and two HV diodes. It would
    likely take up less space than the xfmr footprint, and likely cost
    less as well.
  8. Tom Bruhns

    Tom Bruhns Guest

    Amplifying on what JoeBloe wrote: Assume one side of the transformer
    secondary is grounded. The other side drives one end of a capacitor,
    C1. The other side of that capacitor goes to the cathode of diode D1
    and the anode of diode D2. The anode of diode D1 is grounded. Thus,
    it prevents the "diode" end of C1 from going significantly more
    negative than ground. The cathode of diode D2 connects to the output
    terminal, and between the output terminal and ground is C2. C2 must be
    rated to withstand the peak output voltage, of course. C1 must be
    rated to withstand the peak transformer voltage, roughly half the peak
    doubler output voltage, and in addition, must be insulated from its
    surroundings so that when the diode end reaches the circuit output
    voltage, there will not be unwanted arcs. Each diode must be rated to
    withstand the full output voltage when reverse biased. The diodes must
    not have so much stored charge that they won't recover quickly relative
    to the switching rate at which you are driving the transformer. The
    value of the capacitors must be such that they do not discharge
    significantly over the course of a cycle. You can determine how much
    charge is removed from C2 by the load during one cycle, and that charge
    must be replaced each cycle by C1. Note that the peak diode current
    will be considerably more than the load current, since the diodes
    conduct in relatively short pulses. The amount of charge and the
    capcitance will tell you how much ripple voltage there is, and how much
    the output voltage is below the peak-to-peak transformer voltage. Of
    course, you also must consider diode drops and drops in the transformer

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