"The Natural Philosopher" wrote in message
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Fred wrote:
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Bob Mannix wrote:
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Bob Mannix wrote:
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Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
The commutator is to ensure the field
in the rotor is aligned wrt the stator to provide continuous
torque. Not sure where you get 3 phase from.
Each winding gets an AC signal.
No - it gets switched polarity DC. A different thing entirely.

NO, it is true alternating current in the meaning of the term.
Current that has an average value of zero, but has at any given
time, a value that is not zero.

Err no, it's *an* alternating current in *your* meaning of the term
"True" alternating current is that whis is assumed in AC theory and
engineering and in the design of AC motors and equipment and is
sinusoidally varying.


Er, no, sinusoidal is not mentioned anywhere in the *definition* of
AC.
Oh well, that's all AC current theory out the window then, so that's
OK!


Not at all. Sinusoidal merely makes it easy to do calculations based on
single frequency operation.

In te real world, its almost never seen ourtside of ultra low distortin
oscillators.

You have to distinguish between 'electrical theory for dummies' and
'electrical engineering, an advanced course'

Agreed!

To get the advantages of 3 phase, each waveform has to be close to
sinusoidal.


No it doesn't.

3 phase as far as a motor is concerned, simply means it knows which way to
go round.

What on earth are you talking about? Are you seriously suggesting that it
doesn't matter what the waveform is for each of the phases, that you can
still tell me which way the motor will turn? Wow.