# Re: MOT Voltage Doubler

```At 06:11 20/09/98 -0600, you wrote:
>Original Poster: "Gregory R. Hunter" <ghunter-at-enterprise-dot-net>
>
>Dear List,
>
>I've been studying the half-wave voltage doubler circuit (MOT, cap, diode)
>found in US-type microwave ovens, and I think I understand how it works.
>What is the ultimate voltage developed by this thing.  Looks like 2.8 x
>RMS.  Is that it?  If I'm correct, then it doesn't really "double" anything
>does it?
>
>Greg
>

Greg, check this my old mail below:

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).

________________________________________________________________________

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...
________________________________________________________________________

```