[BC] Odd request....

[RichardBJohnson at comcast.net]

The dimension of the magnetic field in a coil, transformer, etc., is in volt-seconds. That's the voltage-per-turn and the reciprocal of the frequency. Transformer iron, i.e., 2% silicon steel, saturates at about 1 kilogauss. The mean magnetic path length within which that "turn" runs controls the magnetic field. Basically, from transformer charts at 60 Hz, if you want 1 volt-per-turn, i.e., 120 turns for 120 volts, you are going to need a mean magnetic path length of about 6 cm (the length around the coil. That makes your 120-volt transformer 1.5 cm l, 1.5 cm w, 1.5 cm h, minimum. A piece of 20A wire will not fit on something so small. One turn with 20 A would produce 20/120 of an ampere in the secondary. To get your 120 volts, you need R= E/I = 120/1.6666 = 72 ohms. This would eat way too much power. You need more turns meaning a larger build.

20 A current transformers are large.

Cheers,
Richard B. Johnson
Book: http://www.AbominableFirebug.com/

----- Original Message -----
From: "Cowboy" <curt at cwf1.com>

On Thursday 14 June 2012 11:39:51 am Cowboy wrote:
> On Thursday 14 June 2012 09:16:42 am RichardBJohnson at comcast.net wrote:
> > Use a filament transformer with a 10A secondary.
> 
>  Thought about that. ( one of the first things I'd thought of )
>  Too big, physically.
>  Needs to fit in a quad-box.

 What's currently ( no pun intended ) looking most promising
 is about ten wraps around the solenoid of an old clock motor.