Re: TC efficiency, was Math help...

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 7/13/01 12:24:29 AM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

> 
>  In a message dated 7/12/01 7:16:57 PM Central Daylight Time, tesla-at-pupman.
> com 
>  writes:
>  
>  <<  I would say that large coils are more
>   efficient than small ones, mainly because various transformer
>   % losses are lower in larger transformers.
>    >>
>  Hi John,
>  I gotta ask why? I assume by % losses you mean power out over power in. 

Hi Ralph,

If the transformer's linear dimensions are increased by factor k,
the flux and current are muliplied by k squared.  Since flux is
proportional to voltage, the VA rating of the transformer is 
increased by k to the 4th power.  But the core losses and
copper losses are mulitplied by k to the 3rd power.  Thus the
VA rating increases faster than the losses as the transformer
size in increased, making large transformers more efficient, 
assuming equal quality for the iron and copper in the transformers.

John Freau
--

> Would the 
>  transformer efficiency not depend on the geometry of the transformer core? 
I 
> 
>  am
>  thinking (?) that a core constructed longer than the winding might produce 
a 
> 
>  flux more perpendicular to the plane of the winding and so have greater 
>  linkage with the windings. The properties of the steel will also determine 
>  the amount of input power lost to eddy currents
>  and hysteresis.
>  
>  Happy day,
>  Ralph Zekelman
>