# 8kV MW oven supply and spark gaps (fwd)

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---------- 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- |----|    |----|    |----|

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...
________________________________________________________________________

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