Re: Redundant power supplies

On Sat, 26 Oct 2024 23:54:01 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

Most of my boxes have dual power supplies.  Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
>

What kind of 'boxes' are you talking about?
Redundancy is seldom a feature outside the military,
telecom, life-support or un-interruptible fields.

I have always *assumed* they were configured to SHARE the load.
>

Sharing is not a feature required for redundancy.
Failure isolation IS.

I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??).  And, when in the redundant configuration,
allows me to choose which is the "primary".

The former doesn't make any sense - the latter is a simple matter
of voltage adjustment differential and degrees of slope compensation
in the sharing scheme. Some digital/software guys can get carried
away - offering features that don't make any particular sense,
just because they can . . . . . Simple is usually better when it
comes to power delivery, regulation and security.

>
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
>
Is there any advantage to this over a "sharing" configuration?

Switch-over and single-fault failure characteristics can vary
between different set-ups. The aim is to provide minimal
disturbance to the system when one unit fails, or when one
unit has to be hot-swapped out.

Hot-swapping is not automatically feasible, just because there
are two power supplies in parallel. It could be that the
option to select a 'primary' unit is a crude attempt to
provide quasi hot-swap capability.

 
And, why would I ever want to *disable* PFC?

Non-sequitur. Power Factor Correction has nothing to do with
redundancy. See previous comments re digital/software.

RL