Re: [CAD_CAM_EDM_DRO] Re: 8-wire 1/2coil stepper?

Tony,

You are missing the difference between a unipolar drive and a bipolar drive.
It is not that you are using 1/2 the coil that makes the drives different.
Take a look at:
http://www.wirz.com/stepper/phasesqe.html
to see that a bipolar will give more torque.

Tim
[Denver, CO]

----- Original Message -----
From: "Tony Jeffree" <tony@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, May 08, 2002 1:45 PM
Subject: [CAD_CAM_EDM_DRO] Re: 8-wire 1/2coil stepper?


> At 17:14 08/05/2002 +0000, you wrote:
> >Bipolar 1/2 coil vs bipolar parallel or bipolar series is not the same as
> >unipolar rating. You are correct that there is about a 30% greater torque
> >when using a biploar driver vs a unipolar driver. But, there is only a
few %
> >difference between the various bipolar connections.
>
> Correct me if I'm wrong, but I believe that if you are only using 2 coils
> of an 8-wire motor, you should be using the unipolar current rating, and
> will get broadly the same performance as you would with a unipolar drive
> (assuming the same supply voltage in both cases). The 30% advantage with
> bipolar drive is a consequence of being able to parallel connect the coils
> & uprate the (unipolar) current by 1.41 (or series connect coils &
downrate
> the current by 1/1.41). I quote from Marris's post back in January
(message
> 36945):
>
> "If an 8-wire motor has a 1A unipolar rating and you have a full step or
> half step drive, then:
>
> Use 1A if you are running the motor with a unipolar drive (6 wire)
>
> Use 1A if you are running half-winding bipolar
>
> Use 1.41A if you are running parallel bipolar
>
> Use 0.707A if you are running series bipolar
>
> .....
> <The rest snipped>
> .....
> "
>
> Regards,
> Tony
>
>
> >Tim
> >[Denver, CO]
> >
> >-----Original Message-----
> >
> > >Its not necessarily just 3% difference - it depends greatly on the
motor
> > >spec. For example, take a look at:
> > >
> > >http://www.mae.it/us/2231.htm
> > >
> > >This 8-wire motor (RH column of the table) is quoted as giving 30% more
> > >holding torque when bipolar parallel connected vs. unipolar connected.
They
> > >uprate the current by a factor of 1.4 for bipolar parallel connection
(or
> > >downrate by 1/1.4 for series connection).
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
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