"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.

The second phase -- or the shifted phase, actually -- just smooths out the
torque. And, of course, it makes the motor self-starting.


Motors designed to be capacitor-run are two-phase motors. The
advantage is smoother operation at rated load, much less torque ripple
hence much less vibration. In a well-balanced polyphase motor torque
ripple is zero. Capacitor run motors are usually employed in apps
where the load is quite predictable. Once example is a buffer,
another is a blower. There is no separate start cap or centrifugal
switch on my cap-run 2HP buffer.

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.

--
Ed Huntress


I would presume that the gadget in question dispenses with the
capacitor and drives both phases of the motor in proper phase
relationship regardless of frequency.