[Boatanchors] 120 - 240vac and output

[Ron]

Nice post and good analysis on the transformer.
Brian's post on S units is correct .

I agree with Gary that the discussion was about the I*2R drop in the 
mains and not specifically about the transformer where the fellow with 
the amp wanted to use the same house wiring at 240  instead of 120. ( 
BTW , if anyone should do that , make sure you mark the white wire with 
red tape at both ends to indicate that it is the other hot lead and not 
the neutral.)
My post was to try to get these fellows away from working the losses 
using voltage when the current determines the losses. Transformers are 
current devices and voltages are dependent on core flux by E =4.44 f x N 
x Phi max  ( for a sine wave where f is frequency and N is turns Phi max 
is the peak core flux) All examples given are assuming that the high 
voltage secondary will not move under load or is not loaded at all.  The 
secondary current drawn from the non-linear load  (3-500Z. 572, 
811...does not matter)is reflected to the primary.  Currents are 
determined in primary and secondary and then losses in the primary and 
secondary are calculated .  If you want to calculate flux and eddy 
losses ...OK there are formulas for that.  If you want to figure stray 
losses ...OK too.
If you want to just get a rough estimate ...then work the voltages as 
you have been doing and that's OK too but then all you ever learned was 
how to get a reasonable guess.
 
I normally wouldn't have said anything until the post about the signal 
strength vs power just set me off.....sorry.
---
Ron


WA5CAB at cs.com wrote:

>Actually, that isn't generally the case (this 4X figure that has mysterously 
>shown up in several posts).  I've been busy and kept thinking that one of the 
>other EE's on the list would speak up.  But much of what's appeared in this 
>thread simply isn't true.
>  
>
snip