"Zenon"

When sizing the wire size for a power transforner sec. am I right in
assuming that for a non centre-tapped secondary using a silicon bridge
rectifier the wire size will need to be twice the x-section to that of a
centre-tapped secondary using a GZ34 tube rectifier.


** Or maybe a bit more than double since there is no significant voltage
lost with diodes allowing a lower winding voltage .


Logic leads me to believe that a non centre-tapped sec. carries the full
load where a with a
centre-tapped sec. each half carries only half the load hence need only
half
the cross-section.


** More precisely, the halves of a CT winding carry the same size current
pulses as with a bridge rectifier but in only one half at a time. The
winding resistance is double with the thinner wire so the voltage drop
during each pulse is doubled and the total heat loss in the secondary is
doubled too - compared to having one winding and a bridge rectifier.



A centre-tapped sec. has twice the number of turns and if
I use the same wire size as for a non centre-tapped sec. there isn't
enough
room to fit the turns on. Going to a larger core size for a larger winding
window defies logic as the power requirements havn't increased.


** It does not defy logic at all - using a CT secondary with a tube
rectifier ( or two SS diodes) is less efficient than a single secondary with
a bridge rectifier. You need to use a bigger tranny for the same DC power
output with the CT arrangement.




............... Phil