On Mon, 3 May 2010 09:14:52 -0400, "Ed Huntress"
wrote:
"Don Foreman" wrote in message
.. .
On Sun, 2 May 2010 06:42:14 -0400, "Ed Huntress"
wrote:
"Winston" wrote in message
...
On 5/1/2010 9:32 PM, Don Foreman wrote:
(...)
A capacitor-run induction motor is actually a two-phase motor that
produces a rotating magnetic vector.
http://www.electrical-contractor.net...y/msp2v_01.gif
So, if the claims that were *actually* made in the original
source document were (for all intents) the same as the claims
that I dreamt up, then it is highly likely to be fraud because
the magnetic displacement of the second phase will not occur
at the proper time to support armature rotation, given a
significantly different operating frequency?
--Winston --- Or...... not
Keep in mind that I didn't even try to read the original, but Don's
description of a capacitor-run motor, while accurate, doesn't explain the
whole situation.
Once a motor is running, it doesn't need the second phase. Furthermore,
the
second phase only needs to be strong enough, and close enough to proper
phase, to keep the motor moving until it picks up a driving pulse from the
primary phase. The capacitor typically doesn't produce a perfect
"in-between" phase anyway, even at the designed frequency.
A motor designed to be capacitor-run definitely needs the second
phase.
Hmm. If you mean that it "needs" it to run well, then yes. But I don't think
it needs it to run, Don.
As Clinton might have said, "define run". It can limp without it once
started, but it needs it to deliver rated performance. If it can't
meet load while limping then it will stall, which always results in
functional failure and usually results in smoke.
The second phase -- or the shifted phase, actually -- just smooths out the
torque. And, of course, it makes the motor self-starting.
There is no difference between "second phase" and "the shifted phase
actually" because a second phase can only be defined by a phase shift.
A device intended to drive a two-phase motor would make said second
phase in phase quadrature with said first phase regardless of
frequency, and the two phases would be similar or ideally identical in
magnitude. This can be approximated by a capacitor in fixed-frequency
cases with predictable load as previously explained.
A second phase doesn't just smooth out the torque; it is not
subordinate in importance or contribution. In a properly-excited
polyphase motor, all phases contribute equally to output power. A
capacitor-run two-phase motor approaches this at design frequency
while driving approximately design load. An external generator or
producer of a quadrature second phase of similar magnitude to first
phase would significanly ameliorate dependence on both load and
frequency.
I'm going to leave this discussion and let Winston study it on its own. In
my experience, the motors used for blowers are almost always permanent-split
capacitor motors, not capacitor-run. But my experience is pretty old. g I
don't want to confuse things here with terminology.
Terminology like "permanent split capacitor" perhaps? Induction motor
technology is considerably older than we are, terminology hasn't
changed in decades.
Ed, being an editor does not qualify you as an engineer any more than
being an engineer qualifies me as an editor. You have plenty of
credentials and know a lot of stuff, don't need to fake. You are one
of few posters on this NG I respect most days ... not including today.