RE: Egg of Columbus Progress

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>

Hi Christoph,

Thanks for the advice... I followed your direction and wrapped 10 turns of
12AWG solid around the core. I connected it to a variac and monitored the
voltage and used a clamp on current meter to watch the current. I've noticed
that the amp meter is a little off, so these numbers may seem somewhat high,
but they should be close.

08.0V = 3.07A
10.0V = 6.57A
12.0V = 27.62A
14.0V = 63.15A

As I got to 14 volts, a little smoke came out from the 35A variac brushes so
I didn't go further. So based on your notes below, it seems like 11 or a
little over 11 volts is the saturation point.

If I am following your math properly, that gives me 100 turns. But it's not
clear to me if you mean per coil, or per phase. Keep in mind that there will
be 4 coils, two connected directly (or possibly with a resistor in series to
create some lag) and then the other two connected through a set of caps to
mimic another phase.

Also, have a look at this:

http://www.teslauniverse.com/images/egg_of_columbus/egg_schematic.jpg

If I'm reading this correctly, the drawing is saying that coils A and B are
one phase and C and D are the other. I'm basing this on the N's and S's
which mean North and South poles I'm guessing. The drawing makes it
difficult to tell how the coils are connected, but it almost looks like the
N coils are in series and the S coils are in series, but one end of the S
windings are going to one phase and the other end is going to the other
phase. Surely this can't be correct.

What do you think?

Thanks,
Cameron


> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Wednesday, September 20, 2006 4:54 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: Egg of Columbus Progress
>
> Original poster: "Christoph Bohr" <cb@xxxxxxxxxxxxxxx>
>
> Hello Cameron.
>
>  > Speaking of wire, I'm thinking about using 12 AWG. I am not sure about
> the
>  > amount of turns. My guess is it's going to be a trial and error kind of
>  > thing.
> only one try, no errors needed ;-)
> just wind some turns of scrap wire on the core, feed the coil with a
> variac
> and check for incresing current at some voltage when the core saturates.
> Adjust a voltage just low enough so that saturation does not take place.
> Divide the voltage by the amount of turns to get the volts/turn ratio.
> Divide 220/110 by the v/t ratio and get the number of turns you need.
> I am not perfectly sure, but I would say, that the total number of needed
> turns divides up onto the two coils that are connected together ( 180°
> apart ).
> Maybe another number of turns might even be better, but I would not go
> below the numbers you derive from the process described above
> Note that the presence of the egg might influence the inductance.
>
>  > The museum egg has around 82 turns per coil of what appears to be 12
>  > AWG cotton covered wire.
> I wound a variac some time ago on a similar sized core and ended up with
> 170 turns for 220V service, so 82 turns seems to be in the right order.
>
>  > Any thoughts or comments on this would be appreciated.
> you read it...
> you can not unread it ;-)
> Hope this helped a little, great project by the way and very nice
> workmanship,
> maybe I will find the chance to build my own some time in the future.
>
> best regards
> Christoph Bohr