[R-390] Power Supply, Capacitors, and Dead Horses

[Bill Hawkins]

It only looks like a dead short on the schematic. The
rectifier has internal resistance, the transformer
windings have resistance, and the core has non-linear
resistance. It definitely will not support infinite
current. Capacitors are not perfect, either.

Rectifiers have a single cycle surge current rating
that is 10-20 times the continuous rating. This, and
the impedance of the components is what allows modern
power supplies to work. If you add more resistance
you run into lower output voltage than you'd think.
This is because the rectifier only conducts during a
small part of the cycle, determined by the ripple
voltage.

Regards,
Bill Hawkins

Scott, Barry (Clyde B) said:

Sometime during the night last night, I happened to think of something
relative to the power supply filtering thread.  With a single cap across the
rectifier, when power is applied, isn't the current demand on the
transformer and rectifier components nearly infinite?  Is this a potential
problem?  Should there be some kind of current-limiting resistor (or other
component) in series with the cap?

So far, it works okay and I realize this sudden current demand is short, but
is this something to be concerned about?

Thanks again,

Barry(III) - N4BUQ