"Don" wrote in message
...
On Jul 30, 12:19 pm, "Ed Huntress" wrote:
"Don Foreman" wrote in message
...
On Fri, 30 Jul 2010 09:38:42 -0400, "EdHuntress"
wrote:
"Joseph Gwinn" wrote in message
...
In article ,
"EdHuntress" wrote:
"Don Foreman" wrote in message
m...
On Tue, 27 Jul 2010 14:19:15 -0400, "EdHuntress"
wrote:
But it was
apparent to me from the time you first commented that you must have
been
absent the day they explained internal phase relationships and
force
in
single-phase motors. g You went so far off base, contending that
those
motors operate inquadratureand so on (most inentionally do *not*
operate
inquadrature; it's part of their design to have partially-shifted
phases)
that I didn't even respond to much of it.
Engineers refer to aquadraturecomponent in any case where there is
phase difference. It's standard notation. However slight the phase
difference is, aquadraturecomponent is necessary to develop torque.
The engineers I know, and the electronics I learned when studying for
both
my amateur and commercial radiotelephone licenses, mean a 90-degree
phase
shift -- pi/2. Anything else is a phase shift of different
proportions --
notquadrature.
What kind of engineers call any phase shift "quadrature"?
Mathematicians
use
different meanings for the term, referring to different processes of
integration, but I've never heard that usage in engineering
applications.
The critical word is "component". Any angle can be resolved into the
sum
of an
in-phase component and aquadraturecomponent.
http://en.wikipedia.org/wiki/Phase_%..._and_quadratur....
29_components
Joe Gwinn
Of course. But to be "inquadrature" means that the phases are displaced
by
90 degrees. Anything else is some other phase shift.
Any phasor can be expressed as the vector sum of an inphase component
and aquadraturecomponent, wherein thequadraturecomponent is
displaced from the inphase component by 90 degrees.
Of course. But you weren't talking about a complex phase relationship. You
were talking about a second phase that was "inquadrature." You can find
definitions for "inquadrature" in any technical resource. It means related
as per a quadrant of a cycle -- in other words, displaced by 90 degrees
from
the reference phase.
I decribed the *real* phase relationship as a phase shift that wasn't
"inquadrature." You scoffed. d8-)
I scoffed at your introduction of the notion of a "drive pulse" in an
induction motor with sinusoidal excitation.
But that's precisely what it is. The primary phase is the "drive pulse(s)."
It provides almost all of the drive in a shade-pole motor; *all* of the
drive in a split-phase motor; *all* of the drive in a capacitor-start
motor -- and those are the three dominant types of single-phase motors,
numerically speaking. The two or three varieties of motors in which the
secondary windings are permanently connected (in addition to shaded-pole
types) also, for the most part, derive most of their drive from the primary
phase.
Again, that discussion, from the first post until you introduced the idea of
two-phase motors, was entirely about single-phase motors. In fact, the
entire issue was about motors driven from a single-phase source.
For example, in one of the most common types of single-phase motors, the
basic split-phase, the starting phase lags the primary phase by,
typically,
around 30 degrees.
In this instance, the starting phase could be expressed as the vector
sum (0.866 + j 0.5)M where M is its magnitude. The magnitude of
the inphase component is .866M or M cos (30) that of the
quadraturecomponent is 0.5M or M sin(30).
Yes. But we were talking about relationships that were "in quadrature."
--
EdHuntress-
The two components above are indeed in quadrature, by definition.
Which "two components"? In most single-phase motors, there is NO quadrature
component driving the motor. The 90 degree phase shift provided by
inductance or capacitance in the motor is shifted back (or forward, if there
is a capacitor in the circuit) to some other phase angle before it delivers
magnetic force to the motor. Those motors never actually *run* in
quadrature, unlike a true two-phase motor, which you introduced to the
discussion.
The term quadrature wasn't used in the previous discussion until the
notion of an external two-phase synthesizer
was introduced. Such a device would indeed produce two phases that
are displaced by 90 degrees. The vector sum of these two
components then comprises a rotating vector at synchronous speed.
The discussion was about single-phase motors.
--
Ed Huntress