In article ,
LRod wrote:
On Fri, 18 Mar 2005 00:03:52 -0000,
(Robert Bonomi) wrote:

In article ,
LRod wrote:

I don't remember that being claimed, but I can dispense with it
quickly (I thought I already had in my original response). From the
standpoint of the motor windings, it's always running on 120V. Either
the windings are wired in parallel (120V supply) or the windings are
wired in series (240V). Since the motor windings are always seeing
120V it can't possibly have any different life expectancy based on the
input voltage.

Well, things aren't quite that simple. grin

"All else being equal" -- things like distance from the main breaker
panel, gauge of the distribution wire, etc. -- and which I must note
are usually _not_ equal ;

Points I have often made about 120V vs 240V, some in this thread.

The 240v powered motor tends not to 'bog down' as much / as fast as the
120V powered one. This is attributable to the lower 'line losses' upstream
of the motor, resulting in what is effectively a "stiffer" power supply.

"Stiff" being exactly the term I used in this thread when describing
the supply issues.

Aw shucks, we're having an *agreement*!!! Dammit!

"Amps drawn" goes up as the load goes up, with the supply voltage remaining
constant.

*IF* the supply voltage does _not_ remain constant, but 'sags', the amps
drawn goes up even *more*, to compensate for the 'sag'.

Which is not stiff...

"All things are relative". grin

A result of 'all of the above", plus some other things: voltage sag is
more pronounced and longer duration at 120V than 240V.

Such "parasitic' losses in the motor go up as the *square* of the current.

Yes, I referred to that earlier in this thread. I described it as
voltage drop is four times higher at 120V vs 240V.

This _can_ have an adverse affect on motor longevity.

I didn't connect those dots, but it's also not necessarily a realistic
expectation, either. I can't imagine trying to quantify the
difference.

Quantitative difference depends totally on the *precise* circumstances
involved.

Given _sufficiently_detailed_ information a quantitative evaluation of
reduction in life expectancy is possible. The thought of actually _getting_
said detail in a USENET posting is laughable. It is probably *not*
realistic to expect anyone to have, or be able to produce, sufficiently
detailed source data for such an analysis of a real-world situation.

That said, everything mentioned works _against_ life-expectancy at 120V,
relative to life-expectancy at 240V. 'Best possible case' scenario is that
120V operational life is "as long as" 240V life. If there are _any_
differences, they will be in favor of the 240V operation. "Empirical"
data, from motors in near-continuous use, under varying, but peaking fairly
heavily, load, indicates a 'few' percentage points of life expectancy in
favor of the higher-voltage operation.

I'm taking issue _only_ with the "_can't_possibly_ have _any_ effect on life
expectancy" part of your recent statement.

I'd agree totally with "*probably* won't have any -significant- effect..."

'Possible/probable minor increase in motor longevity' would, it seems to me,
qualify as "one more reason" to favor 240V over 120V wiring; *not*, however,
a 'compelling reason' to change, in and of itself.