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Re: Quiet -off topic

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  • Greg Summerton
    ... Yes Jordan. I believe that some magnetisers charge BIG capacitors to high voltages (and hence, high stored energies) slowly from a small current supply
    Message 1 of 10 , Jun 9, 2005
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      Jordan wrote:

      >
      >I've heard capacitors are sometimes used, to give a big pulse of current.
      >Beyond my ken, but could that help back up the battery power, and reduce
      >the coil/winding requirements?
      >
      >Jordan
      >
      Yes Jordan.
      I believe that some magnetisers charge BIG capacitors to high voltages
      (and hence, high stored energies) slowly from a small current supply
      over time.
      The high voltage in a relatively low value capacitor equates to a high
      stored energy that can be dumped as a high current into a low resistance
      (impedance) electromagnet as a sort pulse.

      The high voltage is from either low-ish power high voltage
      transformers....and sometimes via voltage mulitplying circuits..the
      resultant slow stored but high energy charge is then dumped as a short
      high current pulse into the low impedance electromagnet.

      I did consider this.....but while the cost would not be too high, large
      high voltage capacitors would be more expensive than simple rectified
      (and filtered?..that is the question!) mains.

      However, the attraction of this type of supply is that it uses
      relatively low capacitance, high voltage capacitors to slowly store the
      charge....doing it at low battery voltages would mean that it would need
      VERY high capacitor values, since the stored energy in the capacitor =
      1/2xCxVxV
      Since the energy is a square of the voltage I would need a HUGE value of
      C at low battery voltages, not economic or practical.

      IMO an electromagnet designed with a resistance that gives about 20 amps
      from a full wave recitified 240 volt mains supply is the simplest and
      cheapest, I just need to decided/find out if it needs to be filtered ...
      or not.
      Thanks,
      Greg
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