Re: Continued Problems (fwd)

To: tesla-at-pupman-dot-com
Subject: Re: Continued Problems (fwd)
From: Tesla List <mod1-at-pupman-dot-com>
Date: Tue, 12 May 1998 11:38:44 -0600 (MDT)
Approved: mod1-at-pupman-dot-com


---------- Forwarded message ----------
Date: Tue, 12 May 1998 06:12:57 -0500
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Continued Problems (fwd)

Tesla List wrote:
> 
> ----------
> From:  fxphoto [SMTP:fxphoto-at-centuryinter-dot-net]
> Sent:  Monday, May 11, 1998 2:57 PM
> To:  Tesla List
> Subject:  Re: Continued Problems (fwd)
> 
> Hi Malcom,
>  Thanks for the info. If I am understanding you properly then if I were to
> add a 1H coil to the primary side of a 100 to 1 ratio transformer it would
> show up on the secondary side as an additional 100H inductance.
>  And if I were to put two 100 mH chokes on the secondary side they would
> reflect back on the primary of the same transformer as 2mH.
>                                Thanks again for helping me to understand
>                                 Bill Turbett
> 
> >> Upon further investigation, it
> >> looks like there would be absolutely no affect on the Xl of the secondary
> >> since these devices control the current before it reaches the primary.
> >
> >Wrong. Whatever choke you stick on one side of an ideal transformer
> >appears on the other with its value modified by the turns ratio. It
> >should be remembered that while chokes are at first glance the most
> >innocuous of current limiting devices, they do that with an expense:
> >they store energy in order to do so efficiently (c.f. a resistance =
> >Xl which doesn't and wastes a lot of power). You must model the
> >situation as the primary cap Xc at mains frequency (or break
> >frequency) plus Xl of the choke at whichever frequency is relevant.
> >Just as you use Xc=Xl in the NST situation, you must use the same
> >consideration for any system using an ideal transformer and
> >"limiting" choke. This is the essence of efficient resonant charging.
> >
> >    Re Ed's problem, it is apparent that he is experiencing this
> >phenomenon. There is no other way you can charge the primary cap to
> >beyond the o/c output voltage of the power transformer. The choice of
> >break rate should take account of this.
> >
> >Malcolm
> >
> >
> >

Bill and All,

Close... but no cigar. The transformation is actually a function of the
turns ratio squared. So, in your examples, a 1 H choke on the primary
side of a 1:100 transformer would "look" like a 10,000 H choke
referenced to the secondary side. Similarly, the two 100 mH chokes on
the secondary side will look like an additional 20 microhenries on the
primary side.

-- Bert --