snip


last longer,

Why? Most dual voltage motors run on windings wired series/parallel
(windings are in series with a source of 230V; parallel with a source
of 115V). In other words, regardless of how they are powered the
windings are always seeing 115V. So how would a motor running with
115V on its windings last any longer than a motor running with 115V on
its windings (or run any smoother/quieter)?

Well, cuz of the old I^2*R effect in the windings, there will be only 1/4
as much heat generated in the windings and...


I think you are mistaken about the I^2*R effect in the windings. As I
understand it, each winding sees the same voltage and has the same current
flowing through it whether wired in series or parallel, so the power
dissipated by the windings will be the same in either case. The issue of
only needing 1/2 the current when using twice the voltage applies to the
wiring going to the motor.
For example, assume a motor has two windings where each winding draws 8 amps
with 120 volts across it. There are two options on how to supply the power
to the motor:
(1) Connect the windings in parallel; in this case you need to run a 120V
supply to the motor and the total current through the supply wires would be
16 amps (each winding sees a 120V drop and has 8 amps flowing through it).
(2) Connect the windings in series; in this case you need to run a 240V
supply to the motor and the total current through the supply wires will be 8
amps (each winding sees a 120V drop and has 8 amps flowing through it).

BadgerDog