[time-nuts] Power glitch - Sat morning

[Poul-Henning Kamp]

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> (I recall that correct wiring of the phases / phase rotation was very important vis a vis backup power sources for data centres.)

For anything but resitive heating, you 100% want to have the order
of your three phases under tight control (said the 14 year old kid
who fixed the frayed cable on the grain elevator, only to have it
run backwards :-)

If you have multiple power feeds for redundancy, you will also have
to care about not only their order but also the absolute phasing
between them - ie "rotating" the three phases of one feed to align
them.

But depending on the local circumstances, that may still leave you
with too much phase-skew and you will have to install a "W"
transformer to twist one of the feeds 30 degrees.

If you're going "Say what ?!" it is fully understandable, but
yes, you can rotate the phase between primary and secondary in
steps of 30 degrees with a three phase transformer:

https://electrical-engineering-portal.com/understanding-vector-group-transformer-1

Many data-centers these days bypass all that trouble, by having
separate HVDC busses for each feed, so that they only have to
synchronize the "internal" grid, but that takes us into serious
high power EE.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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