Re: [CAD_CAM_EDM_DRO] Re: Info from Ah-ha! on BOSS's/Motors/HVdrivers

> There is less than a 2 to 3% "performance hit" running a motor in
> half-winding instead of parallel. Let's take your 4.7A motor and 48V
> power supply as an example. It is probably a 1.7 volt motor. If it
> were wired in parallel the coil resistance would be halved and it
> would drop .85 volts instead. Since motor power is proportional to
> voltage, and this voltage subtracts from the power supply, what you
> have is:
>
> Half-winding: 46.30V ( 48 - 1.7 )
> Parallel: 47.15V ( 48 - 0.85 )
>
> Taking the ratio of the two, the half-winding motor "sees" 98% of the
> voltage the parallel motor "sees", for a performance loss of 2%. At
> higher speeds where inductive reactance dominates and phase currents
> drop, this loss fades into insinificance ( << 1% ). Apart from I
> squared R losses at low speeds, there is no advantage to parallel
> connecting the motor.
>
> Mariss

If each half of the winding has a given electrical inductance L, then
putting the two halves in parallel would give an inductance of L/2,
and half the inductive reactance (or a quarter of that found in series
connection). In the regime where inductive reactance is dominant,
won't this make a huge difference?

Am I missing something? Does the fact that the two inductors are
wound together mean they don't add the way isolated inductors would?
(ie, one could argue two pieces of wire wound in parallel around the
same core are really the same as one piece of bigger wire)

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
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