According to Jon Elson :


Randy wrote:
OK, we rule out 400HZ as too high, due to the 1/4 wave length problem,
would it be worth while to go to 90 or 120HZ?

One could argue the thing forever, as the losses are almost all
engineering tradeoffs when the various components are designed.

But, it is all moot. I have no way to calculate the cost, but if the
entire generating, transmission and distribution system had to be
replaced, plus most appliances more complicated than a toaster or light
bulb, the cost would certainly be in the trillions of $.

Hmm ... the universal motors would probably still work
reasonable well -- mixers, hand-held electric drills, toolpost grinders
and the like. But most induction motors would have to be replaced, or
at least the start capacitance value changed (e.g. in single-phase
lathes and the like), or the run capacitance values (in things like my
air conditioning compressor and the associated fan, both of which use
phase-shift capacitors -- to run what I think are actually three phase
motors from single phase power.

For that matter (assuming that we are only talking about 120 Hz,
not 400 Hz) -- four-pole three-phase motors running lathes and milling
machines would probably handle the switch with only an increased speed
as a result, though two-pole ones might risk centrifugal disassembly of
the rotor. :-) For those which could handle the switch, we would
probably have to change pulleys to keep the speeds reasonable -- or to
hang a VFD between each motor and the new higher-frequency three phase,
which would at least isolate the motors from the frequency change.

I'm glad that you covered the question about insulation -- it
saves me the trouble, and makes me glad that I read the followups. :-)

As for the transmission lines, I notice that the high-tension
three phase lines every few towers appear to interchange two of the
three wires -- I guess making the equivalent of twisted pair wiring to
minimize radiation by canceling from the other phase. I suspect that
the interchanges would have to be redone to be closer together at a
higher frequency.

Enjoy,
DoN.

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