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Capacitor charging

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  • xraygunner
    I know this is geared more toward VanDeGraaff generators and such, but I was hoping I might get some insight on charging a capacitor. I started out wanting to
    Message 1 of 5 , Aug 25 5:27 PM
      I know this is geared more toward VanDeGraaff generators and such,
      but I was hoping I might get some insight on charging a capacitor.

      I started out wanting to build a vandegraaff, but soon found that a
      voltage multiplier would suit my needs better. I still follow the
      group as there are things in here that apply to what I'm doing.

      Right now I am in the process of building a capacitor that I would
      like to charge with approximately 85-100kv. The problem seems to be
      that I cannot find any diodes that would serve as the gatekeeper to
      the business end of the capacitor that are in the kv range that I'm
      looking for. Are there any alternatives that I am overlooking?

      It seems that when I look into diodes with voltage ratings that high
      they begin to have "rectifier" in the name, and as far as I know I
      don't need that. I did however find this...

      http://www.edidiodes.com/partnumbers.asp#hvassemblies

      It's a part listed under the "High-Voltage Assemblies" series CYL.

      Any ideas?

      Thanks alot,

      Troy
    • Bert Hickman
      Hi Troy, ... A properly designed voltage multiplier can work quite well for capacitor charging. For example, by using a number of identical lower voltage
      Message 2 of 5 , Aug 27 9:11 AM
        Hi Troy,

        xraygunner wrote:
        > I know this is geared more toward VanDeGraaff generators and such,
        > but I was hoping I might get some insight on charging a capacitor.
        >
        > I started out wanting to build a vandegraaff, but soon found that a
        > voltage multiplier would suit my needs better. I still follow the
        > group as there are things in here that apply to what I'm doing.

        A properly designed voltage multiplier can work quite well for capacitor
        charging. For example, by using a number of identical lower voltage
        stages, a Cockcroft-Walton (C-W) multiplier can multiply the incoming AC
        voltage using lower voltage, more easily available, and less expensive
        capacitors, rectifiers, and HV transformer. For example, you could use a
        10 kV RMS transformer to drive a four-stage C-W multiplier to deliver an
        output voltage in the range you want. You may need to immerse the entire
        assembly in mineral oil to prevent excessive corona or flashovers.

        A couple of useful pages that explain theory of operation, design
        equations, and a Java design aid can be found in the following URL's.
        BTW, when using the Java design tool, select "CW type" for the
        Multiplier Type:

        http://www.blazelabs.com/e-exp15.asp
        http://www.blazelabs.com/cw-brm-java.asp

        >
        > Right now I am in the process of building a capacitor that I would
        > like to charge with approximately 85-100kv. The problem seems to be
        > that I cannot find any diodes that would serve as the gatekeeper to
        > the business end of the capacitor that are in the kv range that I'm
        > looking for. Are there any alternatives that I am overlooking?

        Be extremely careful - HV capacitors can be lethal. Also, if you plan to
        suddenly discharge this capacitor using a spark discharge, you'll need
        to first disconnect your charging circuit to prevent your HV diodes from
        getting zapped by the oscillatory discharge and/or EMP. A small X-ray
        transformer (driven from a variable voltage transformer or Variac) and a
        X-ray rectifier stick could also be used to directly provide HVDC in
        this voltage range. These can sometimes be found on eBay at reasonable
        cost. Again, be extremely careful... =<:^O

        >
        > It seems that when I look into diodes with voltage ratings that high
        > they begin to have "rectifier" in the name, and as far as I know I
        > don't need that.

        Don't be overly concerned about the terms "rectifier" or "diode" since
        they are sometimes used synonymously. ALL high voltage rectifiers above
        a few kV are made up of strings of lower voltage diodes connected in
        series, and the entire assembly is then called a HV rectifier.

        I did however find this...
        >
        > http://www.edidiodes.com/partnumbers.asp#hvassemblies
        >
        > It's a part listed under the "High-Voltage Assemblies" series CYL.
        >
        > Any ideas?
        >
        > Thanks alot,
        >
        > Troy

        Most hobbyists purchase HV rectifiers off the surplus market or roll
        their own because of the high purchase cost for new HV rectifiers. EDI
        would be an excellent source. Since you're dealing with low current,
        their BCD/RTD or LHC25/RHC25 series would also work nicely in a C-W
        multiplier. The CYL series may be overkill for your application unless
        you plan to directly use an X-ray transformer as your supply.

        Remember that the peak discharge current from charged HV capacitors can
        be vicious. If you accidentally get across a charged cap, the resulting
        muscle contractions can literally throw you across the room. The shock,
        if properly timed, can also send your heart into fibrillation. Never
        work with this stuff alone, and always remember to discharge EVERY HV
        capacitor in the circuit before working on any portion of your system.

        Good luck,

        Bert
        --
        ***************************************************
        We specialize in UNIQUE items! Coins shrunk by huge
        magnetic fields, Lichtenberg Figures (our "Captured
        Lightning") and out of print technical Books. Visit
        Stoneridge Engineering at http://www.teslamania.com
        ***************************************************
      • Dave Jenkins
        If you are using a voltage multiplier/adder the output is allready DC at the output. 100kV you must be talking about a Cockroft Walton style adder. If you re
        Message 3 of 5 , Aug 27 2:18 PM
          If you are using a voltage multiplier/adder the output is allready DC at the output. 100kV you must be talking about a Cockroft Walton style adder. If you're charging a cap after the adder you might need a high meg resistor string to prevent damage to the adders rectifiers.
           
          Sourcing and purchasing "new" HV diodes is a pain.. There isn't much demand for them and new HV rectifier stacks cost too much. You're better off buying them surplus. Go to ebay and search for rectifier diode or High voltage diode. You will find some there at a fraction of the original cost.
          You didn't state the operating frequency of your multiplier... Rectifiers come in two flavors, standard and fast recovery. Standard is typically 50 to 60 Hz (or a little more) and fast recovery is for high frequency rectification.
          A source for 100-150kV rectifier stacks is from X-Ray machines. They are sometimes sold on ebay also. These stacks are strings of diodes placed in series and run at 50 to 60Hz.
           
          You can build your own rectifier stack. Say you want to rectify 100kV. Buy 300 of the very common 1N4007 1 Amp/1000 Volt diodes and wire them in series in a zig zag layout. This will give you a 300kV rectifier. Typically you need to run stacks like this at 1/3 their rated voltage and it's preferable all the diodes come from the same manufacturing batch so the characteristics of each diode are close. Also single diodes/rectifiers rated for a certain voltage should usually be run at 2/3 their ratings.

          --- On Mon, 8/25/08, xraygunner <xraygunner@...> wrote:
          From: xraygunner <xraygunner@...>
          Subject: [VanDeGraaffGenerator] Capacitor charging
          To: VanDeGraaffGenerator@yahoogroups.com
          Date: Monday, August 25, 2008, 5:27 PM

          I know this is geared more toward VanDeGraaff generators and such,
          but I was hoping I might get some insight on charging a capacitor.

          I started out wanting to build a vandegraaff, but soon found that a
          voltage multiplier would suit my needs better. I still follow the
          group as there are things in here that apply to what I'm doing.

          Right now I am in the process of building a capacitor that I would
          like to charge with approximately 85-100kv. The problem seems to be
          that I cannot find any diodes that would serve as the gatekeeper to
          the business end of the capacitor that are in the kv range that I'm
          looking for. Are there any alternatives that I am overlooking?

          It seems that when I look into diodes with voltage ratings that high
          they begin to have "rectifier" in the name, and as far as I know I
          don't need that. I did however find this...

          http://www.edidiode s.com/partnumber s.asp#hvassembli es

          It's a part listed under the "High-Voltage Assemblies" series CYL.

          Any ideas?

          Thanks alot,

          Troy

        • xraygunner
          I guess I should have clarified that, yes I am using a voltage multiplier. I am assuming that it has a standard recovery time. I ll look into that. What I am
          Message 4 of 5 , Aug 27 2:40 PM
            I guess I should have clarified that, yes I am using a voltage
            multiplier. I am assuming that it has a standard recovery time.
            I'll look into that. What I am mainly concerned with is making sure
            that goes into the capacitor I am charging, stays there until
            purposefully discharging. Secondly I want to make sure that the
            discharge doesn't damage anything either. I am planning on a spark
            gap discharge if this helps.

            Thanks again for all the input so far. There is a lot of good help
            and advice out of this group.

            Troy

            --- In VanDeGraaffGenerator@yahoogroups.com, Dave Jenkins
            <davejenkins70@...> wrote:
            >
            > If you are using a voltage multiplier/adder the output is allready
            DC at the output. 100kV you must be talking about a Cockroft Walton
            style adder. If you're charging a cap after the adder you might need
            a high meg resistor string to prevent damage to the adders rectifiers.
            >  
            > Sourcing and purchasing "new" HV diodes is a pain.. There isn't
            much demand for them and new HV rectifier stacks cost too
            much. You're better off buying them surplus. Go to ebay and search
            for rectifier diode or High voltage diode. You will find some there
            at a fraction of the original cost.
            > You didn't state the operating frequency of your multiplier...
            Rectifiers come in two flavors, standard and fast recovery. Standard
            is typically 50 to 60 Hz (or a little more) and fast recovery is for
            high frequency rectification.
            > A source for 100-150kV rectifier stacks is from X-Ray machines.
            They are sometimes sold on ebay also. These stacks are strings of
            diodes placed in series and run at 50 to 60Hz.
            >  
            > You can build your own rectifier stack. Say you want to rectify
            100kV. Buy 300 of the very common 1N4007 1 Amp/1000 Volt diodes
            and wire them in series in a zig zag layout. This will give you a
            300kV rectifier. Typically you need to run stacks like this at 1/3
            their rated voltage and it's preferable all the diodes come from the
            same manufacturing batch so the characteristics of each diode are
            close. Also single diodes/rectifiers rated for a certain voltage
            should usually be run at 2/3 their ratings.
            >
            > --- On Mon, 8/25/08, xraygunner <xraygunner@...> wrote:
            >
            > From: xraygunner <xraygunner@...>
            > Subject: [VanDeGraaffGenerator] Capacitor charging
            > To: VanDeGraaffGenerator@yahoogroups.com
            > Date: Monday, August 25, 2008, 5:27 PM
            >
            >
            >
            >
            >
            >
            > I know this is geared more toward VanDeGraaff generators and such,
            > but I was hoping I might get some insight on charging a capacitor.
            >
            > I started out wanting to build a vandegraaff, but soon found that a
            > voltage multiplier would suit my needs better. I still follow the
            > group as there are things in here that apply to what I'm doing.
            >
            > Right now I am in the process of building a capacitor that I would
            > like to charge with approximately 85-100kv. The problem seems to be
            > that I cannot find any diodes that would serve as the gatekeeper to
            > the business end of the capacitor that are in the kv range that I'm
            > looking for. Are there any alternatives that I am overlooking?
            >
            > It seems that when I look into diodes with voltage ratings that
            high
            > they begin to have "rectifier" in the name, and as far as I know I
            > don't need that. I did however find this...
            >
            > http://www.edidiode s.com/partnumber s.asp#hvassembli es
            >
            > It's a part listed under the "High-Voltage Assemblies" series CYL.
            >
            > Any ideas?
            >
            > Thanks alot,
            >
            > Troy
            >
          • xraygunner
            One more question, folks. I ve been looking into the HV rectifiers and the best I ve found so far is 80kv. Is it possible to connect several in an
            Message 5 of 5 , Sep 2, 2008
              One more question, folks. I've been looking into the HV rectifiers
              and the best I've found so far is 80kv. Is it possible to connect
              several in an arrangement that will give the desired result?

              Thanks again,

              Troy

              --- In VanDeGraaffGenerator@yahoogroups.com, "xraygunner"
              <xraygunner@...> wrote:
              >
              > I guess I should have clarified that, yes I am using a voltage
              > multiplier. I am assuming that it has a standard recovery time.
              > I'll look into that. What I am mainly concerned with is making
              sure
              > that goes into the capacitor I am charging, stays there until
              > purposefully discharging. Secondly I want to make sure that the
              > discharge doesn't damage anything either. I am planning on a spark
              > gap discharge if this helps.
              >
              > Thanks again for all the input so far. There is a lot of good help
              > and advice out of this group.
              >
              > Troy
              >
              > --- In VanDeGraaffGenerator@yahoogroups.com, Dave Jenkins
              > <davejenkins70@> wrote:
              > >
              > > If you are using a voltage multiplier/adder the output is
              allready
              > DC at the output. 100kV you must be talking about a Cockroft Walton
              > style adder. If you're charging a cap after the adder you might
              need
              > a high meg resistor string to prevent damage to the adders
              rectifiers.
              > >  
              > > Sourcing and purchasing "new" HV diodes is a pain.. There isn't
              > much demand for them and new HV rectifier stacks cost too
              > much. You're better off buying them surplus. Go to ebay and search
              > for rectifier diode or High voltage diode. You will find some there
              > at a fraction of the original cost.
              > > You didn't state the operating frequency of your multiplier...
              > Rectifiers come in two flavors, standard and fast recovery.
              Standard
              > is typically 50 to 60 Hz (or a little more) and fast recovery is
              for
              > high frequency rectification.
              > > A source for 100-150kV rectifier stacks is from X-Ray machines.
              > They are sometimes sold on ebay also. These stacks are strings of
              > diodes placed in series and run at 50 to 60Hz.
              > >  
              > > You can build your own rectifier stack. Say you want to rectify
              > 100kV. Buy 300 of the very common 1N4007 1 Amp/1000 Volt diodes
              > and wire them in series in a zig zag layout. This will give you a
              > 300kV rectifier. Typically you need to run stacks like this at 1/3
              > their rated voltage and it's preferable all the diodes come from
              the
              > same manufacturing batch so the characteristics of each diode are
              > close. Also single diodes/rectifiers rated for a certain voltage
              > should usually be run at 2/3 their ratings.
              > >
              > > --- On Mon, 8/25/08, xraygunner <xraygunner@> wrote:
              > >
              > > From: xraygunner <xraygunner@>
              > > Subject: [VanDeGraaffGenerator] Capacitor charging
              > > To: VanDeGraaffGenerator@yahoogroups.com
              > > Date: Monday, August 25, 2008, 5:27 PM
              > >
              > >
              > >
              > >
              > >
              > >
              > > I know this is geared more toward VanDeGraaff generators and
              such,
              > > but I was hoping I might get some insight on charging a capacitor.
              > >
              > > I started out wanting to build a vandegraaff, but soon found that
              a
              > > voltage multiplier would suit my needs better. I still follow the
              > > group as there are things in here that apply to what I'm doing.
              > >
              > > Right now I am in the process of building a capacitor that I
              would
              > > like to charge with approximately 85-100kv. The problem seems to
              be
              > > that I cannot find any diodes that would serve as the gatekeeper
              to
              > > the business end of the capacitor that are in the kv range that
              I'm
              > > looking for. Are there any alternatives that I am overlooking?
              > >
              > > It seems that when I look into diodes with voltage ratings that
              > high
              > > they begin to have "rectifier" in the name, and as far as I know
              I
              > > don't need that. I did however find this...
              > >
              > > http://www.edidiode s.com/partnumber s.asp#hvassembli es
              > >
              > > It's a part listed under the "High-Voltage Assemblies" series CYL.
              > >
              > > Any ideas?
              > >
              > > Thanks alot,
              > >
              > > Troy
              > >
              >
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