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MMD > Archives > January 2013 > 2013.01.12 > 04Prev  Next

Replacement Motors for Electric Player Pianos
By Alan Douglas

Reducing the line voltage to a motor is not really a good idea,
and will make it overheat sooner.  It's the same reason that air
conditioners fail during power system brownouts.

A motor (assuming constant speed) takes a constant power to do its
work.  Power is the product of voltage times current; if the voltage
is reduced, the current must increase.  It is the current through
the wire windings that heats them.

As to line voltages, although people still say "one-ten volts"
and "two-twenty volts" there never was any such standard.  When
carbon-filament lamps were first made, they were graded for voltage
after manufacture since the process couldn't be controlled very well.
Electric companies in various cities were encouraged to standardize
on different voltages, to create a market for all lamps produced.
So the "standard" was anywhere from 110 to 125 volts (125 volts was
mostly direct current).

Over time, higher voltages predominated.  Specifically, in 1919,
115V lamps overtook 110V in popularity.  By 1926 110V lamps accounted
for only 12% of demand, 115V for 47%, 120V for 35%, 125V 4%, and all
others 2% (AIEE Transactions 1927, pp. 161-215).

Motors were designed to run on the normal range of voltages in use at
the time, even though they were marked 110V or, later, 115V.  115/230V
was the proposed standard in 1927.  Later it became 117.5V +/- 7.5V,
and still later (in the late 1940s or early 1950s, I believe) 120V
+/-5% or +/-6V. It is in the power companies' interest to keep the
voltage as high as possible, to get the maximum use from their existing
distribution network.  Mine has been 123V since 1960.

Alan Douglas

(Message sent Sat 29 Dec 2012, 13:48:34 GMT, from time zone GMT-0500.)

Key Words in Subject:  Electric, Motors, Pianos, Player, Replacement

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