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8kV MW oven supply and spark gaps (fwd)



---------- Forwarded message ----------
Date: Fri, 22 May 1998 11:27:33 +0300
From: Marco Denicolai <marco-at-vistacom.fi>
To: tesla-at-pupman-dot-com
Subject: 8kV MW oven supply and spark gaps

Thinking more about my tank supply, I figured out I was wrong with the
voltage waveshape of its output.

                         | |    
       --------|| ||-----| |----*---------- -
             * || || *   | |    |
               || ||          -----
   220V        || ||          \   /
               || ||           \ /
               || ||          -----
               || ||            |
       --------|| ||------------*--- GND
                                |
                                |
       --------|| ||------------*
             * || || *          |
               || ||          -----
               || ||          \   /
    220V       || ||           \ /
               || ||          -----
               || ||     | |    |
       --------|| ||-----| |----*----------- +
                         | |    

If the transformers are in phase, the output (between + and -) is a 8kV DC
oscillating +/- 2kV in respect to ground. But because the + and -
oscillations are in phase, the net potential different between + and - is
always 8kV (i.e. it's a DC output).

  V+ |----|    |----|    |----|
     |    |----|    |----|    |----

 GND ------------------------------     V+ - V- = 8kV DC

     |----|    |----|    |----|
  V- |    |----|    |----|    |----
     
If the transformers are NOT in phase, the output is a kind of pulsed DC,
changing from 4kV to 8kV at a frequency of 50 Hz (60 in US).

  V+ |----|    |----|    |----|
     |    |----|    |----|    |----

 GND ------------------------------     V+ - V- = 4kV to 8kV DC pulsed

     |    |----|    |----|    |----
  V- |----|    |----|    |----|


Anybody has got different opinion about this?

Now, using a static spark gap will probably not work in either cases because
the microwave oven transformers are capable to pump even 500 mA. Or I would
need a jet turbine to quench it.

But what about a rotary spark gap? That should quench in any case and, because
I got almost a DC tank supply, I shouldn't have to bother about being in
phase with the main power supply (220V or 110V).



________________________________________________________________________

 Marco Denicolai                   Vista Communication Instruments, Inc.
 Hardware Development Manager      www.vistacom.fi   

 marco-at-vistacom.fi                 Kaisaniemenkatu 13 A
 fax:    +358-9-622-5610           SF-00100 HELSINKI
 phone:  +358-9-622-623-15         Finland

   Remember, Murphy was an optimist! I am not...
________________________________________________________________________