Re: A little experiment on demagnetization

You can increase current by 1.41 in a parallel connection to get more
holding torque but so what? Power (it's what gets things done) is RPM
times torque, and that does not increase. You simply reach the
motor's rated output a little lower speed.

Past that speed power output stays constant.

We can all agree that power delivered to the motor that goes up as
resistance heating is power not available for some portion to be
converted into mechanical power. On a triple-stack size 34 motor that
is about 6 Watts. Assuming 50% is converted to mechanical power, 3
additional Watts would have been available. For a motor that is
developing 200W mechanical, those 3W amount to 1.5%.

I would welcome anyone to run these tests independently.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "krnldmp <krnldmp@y...>"
<krnldmp@y...> wrote:

> Sure. But in the case of the bipolar two coil motor the coil wire

cross sectional area is doubled to fill the slot space and preserve
motor efficiency. In the case of the unipolar motor pinched into half
coil bipolar operation there might be some waste totalling more than
the one percent the way the writer of "3)" below seemed to suggest.
If one were to opt for full coil utilization of any six wire motor
then the normal bipolar holding power loss would be preserved at the
expense of increasing inductance limiting of useful speed, which is
still losing a lot more than 1% of the available motor should the
thing be re-wired for bifilar two coil operation. If you attempt to
obtain max pole saturation levels (holding torque) through half the
coil, the IR loss doubles, and the motor overheats.

>
> ???? I dunno. I thought that's what the guy asking about re-wiring

for bipolar was looking for, max performance from the motor, a
difference of a lot more than 1%.

>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "jeffalanp <xylotex@h...>"

<xylotex@h...> wrote:

> > Hi,
> > Not to respond for the writer of "3)" below, but, The extra

wire in

> > the stepper motor (the second pair of two coils - 4 coils total),

is

> > needed to allow the stepper motor to be run in unipolar mode. A
> > stepper designed strictly for bipolar use wouldn't need the extra
> > coils and would only have four leads (two coils total).
> >
> > Jeff
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "krnldmp <krnldmp@y...>"
> > <krnldmp@y...> wrote:
> > >
> > > > 3) This voltage drop is meaningless while the drive is

current

> > > > limiting at low speeds.
> > > >
> > >
> > > I don't know if I had too much coffee yesterday and not enough

this

> > > morning, or what, but I'm no less confused now. It seems like

you're

> > > writing that stepper motors could do away with half the wire

used

> > and
> > > not lose any significant amount of performance, and/or, that

stepper

> > > motors aren't thermally limited performancewise.