Re: 8-wire 1/2coil stepper?

--- In CAD_CAM_EDM_DRO@y..., "Tim Goldstein" <timg@k...> wrote:

> 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.
>

...or maybe try:

http://www.cs.uiowa.edu/~jones/step/types.html

which gives a rather different picture (pun intended) ;-)

Regards,
Tony

> Tim
> [Denver, CO]
>
> ----- Original Message -----
> From: "Tony Jeffree" <tony@j...>
> To: <CAD_CAM_EDM_DRO@y...>
> 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
> > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> >
> > OFF Topic POSTS: General Machining
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reach it if

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> >
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