RadioBanter - View Single Post - 13.8V high current power supply

May 11th 06, 09:35 AM posted to rec.radio.amateur.homebrew

On Thu, 11 May 2006 01:04:23 GMT,
wrote:

Limiting inrush current is mostly to protect the diodes as the first
charge the caps. For the first few ac cycles those caps look like a
dead short or mightly close. Under those conditions the diodes have
to stand the short circuit current the transformer can provide which
can easily exceed diode rating if care is not taken.

Also if a toroid mains transformer is used, the transformer start-up
current can be huge for a large (say 1 kVA) transformer, which could
harm the house wiring or burn the fuses in the main distribution
panel.

Depending at what mains cycle phase angle the transformer was
previously disconnected and on what phase angle it is reconnected to
the mains, the start-up peak can be insignificant or the current can
be huge, which is limited just by the copper resistance of the
primary.

Paul OH3LWR