Re: [CAD_CAM_EDM_DRO] Re: 8-wire stepper: series is 1/2 the amps.Strange but True

On Sat, 31 May 2003 20:24:53 -0000, you wrote:

>
>Hi Lee,
> Won't series winding (full winding) RESISTANCE be TWICE the amount
>of the single coil (1/2 coil), while your series winding INDUCTANCE
>be FOUR times that of the single coil (1/2 coil)?
>
> With series winding (full winding), you have twice the number of
>turns of wire being energized as half winding, so you use half the
>amount of current to acheive the same holding torque.

Seems to be two factors here. One is the maximum flux through the
motor, the other is the power dissipation of the motor. The
inductance does relate to the maximum supply voltage needed for "good"
performance.

The motor is not rated (unless it's stated by the manufacturer) for
both halves of a 6 wire motor actuated at once (running unipolar as
bipolar). You have to derate the motor to get this to keep both the
flux (excessive can demagnetize the motor) and the power dissipation
in limits.)

So running both halves of the motor windings (say 4 volts at 2 amps if
unipolar) as bipolar, full coil means that you have an 8 volt winding,
but at about 1.3 amps, assuming a derating factor of 0.66. Using one
coil of a unipolar stepper (ignoring the lead completely, using only
the CT and one wire) will get you the original nameplate ratings.. say
that same 4 volts at 2 amps. You will need a bipolar driver to handle
it, and the easiest one of those is a chopper style driver...

Further complications come when you use 8 wire steppers, which are
steppers with all 4 coils wired independently.

(All the above is what I've managed to piece together, if it's
incorrect, please correct it, and blame it on the lateness of the
hour...)

Harvey

>
>Jeff
>http://www.xylotex.com
>