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8kV MW oven supply measured


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From:  Marco Denicolai [SMTP:marco-at-vistacom.fi]
Sent:  Wednesday, May 27, 1998 12:47 AM
To:  tesla-at-pupman-dot-com
Subject:  8kV MW oven supply measured

I had eventually a chance of performing a real measurement on the circuit
below. I used a digital scope and applied to the mains 3.5 VAC instead
of 220 VAC. After the measurements, I scaled up the results and these 
I am reporting in the following.

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

Voltage V+ to GND oscillates between 6270 V and 0 (2200 VAC * 2 * sqrt(2) =
6270 Vpp). 
Voltage between V- and GND oscillates between -6270 V and 0.
If the transformers are in phase, voltage between V+ and V- is almost DC at
6270 VDC.

  V+ |----|    |----|    |----|
     |    |----|    |----|    |
 GND ------------------------------     V+ - V- = 6.3kV DC
     |----|    |----|    |----|
  V- |    |----|    |----|    |----
     
If the transformers are NOT in phase, the output is a sinusoid at 50 Hz
going from 0
to 6270 Vpp * 2 = 12540 Vpp.

  V+ |----|    |----|    |----|
     |    |----|    |----|    |----
 GND ------------------------------     V+ - V- = 0 to 12.5kV DC pulsed
     |    |----|    |----|    |----
  V- |----|    |----|    |----|

I intend to use the last configuration (transformers NOT in phase, 12.5kV
pulsed output).

I think static spark gaps won't easily quench, for the microwave oven
transformers are 
capable to pump even 500 mA. Instead, a rotating spark gap would be forced
to quench at
my rotating rate.

Any suggestion about the spark gap choice?



________________________________________________________________________

 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...
________________________________________________________________________