RE: ballast

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Dean by way of Terry Fritz <twftesla-at-uswest-dot-net>" <deano-at-corridor-dot-net>

Hi Max,

The frequency would be either 60Hz or 50Hz depending on where you live,
unless you are using a generator or an inverter to power it with. If the
input voltage is 120, then the transformation ratio is 120:1. To get 500mA
out of the secondary would require 60A into the primary. That would be only
30A if the input voltage were 240.

Lets say you put 120V into the transformer and want to limit the short
circuit current to 500mA. A resistor of 2 ohms in series with the low
voltage winding would do that. An inductor with the same reactance would do
the same thing into a short. Things get a bit more complex when you start to
charge a capacitor, but we'll not get into that now.

To find the inductance that will provide the reactance (2 Ohms) at the
frequency of interest, (in the US that is 60Hz) use the formula L = 2
Ohms/2*PI*F    =2/6.28*60 =2/376.8 = .0053H or 5.3mH.
If the input frequency were to be 50Hz, the required inductance would be
6.37mH, if the frequency were 500Hz, the inductance would be 637uH.

later
deano

> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Wednesday, February 21, 2001 9:04 PM
> To: tesla-at-pupman-dot-com
> Subject: ballast
>
>
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <Gbjsjg-at-aol-dot-com>
>
> My Power Transformer is 14400kv and .5 amps. I figured out that
> that ist has
> 2 ohms of reactance. The equation calculate the inductance to limit the
> current is not coming out right.
>
> R= 2ohms of reactance
> F= 500 cycles (right)
> pie= 3.14159
> L= x inductance
>
> L= R*1000
>      2pie*F
>
> So my equation would be-
>
> L=      2*1000
>     2*3.14159*500
>
> Its coming out to a wierd number like .4 something at 120 volts.
> Any help on
> the mh I will need to limit my current? Also does anyone know
> what I should
> use to limit the current?
>
> -Thanks Max Joseph
>
>
>