Bruce in Bangkok writes:


All distribution transformers, sometimes called "pole pigs", that I
have seen had some sort of voltage adjusting system, usually referred
to as taps. Usually they are an actual bolted "tap" and you open the
transformer and set the output voltage by making the proper tap
connection when the transformer is installed and frankly it is usually
ignored thereafter.

The pole pigs here [7200v in/120-240 out] are fixed tap, I'm told. Saves
money. I think they are fused at 10A in. Older ones may have settable taps.

The other "cans" you often see on poles are capacitors used to adjust
the power factor on some secondaries.

Capacitors are in various places but we also have three 7200V line
regulators a block away, one on each primary phase. They are
auto-transformers, with allegedly auto-controlled tap changers, much as
the other poster described. [But his description is more complex than
I recall from the class covering same. The essential aspect was you
CAN short two taps together while switching; the inductance limits the
current change while you do..]

I say "allegedly" as twice now, the regulators have stuck and my UPS
woke me up at 2:30AM with notices it was disconnecting from the now-128v+
line. I solved the issue that night by putting a Variac in the line
ahead of it, and cranking it down.

It took multiple calls and finally PSC [oversight agency] complaints
to get PEPCO to fix the damn thing.

I envy EU houses. If we had regular 240V/30A+ outlets, I'd be able to
buy a snowblower with real guts. The 120v@15A ones are wimpy.
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