RE: [CAD_CAM_EDM_DRO] Re: Tawagawa Seiki steppers

I wasn't making any distinction between 2 or 5 phase and I agree that you
need to consider the other windings.

I also agree that if you short the windings together or to ground that it
will cause braking.

However, if I connect the coil to ground on both ends with an NPN transistor
at each end (and they have sufficient base current to be in saturation) I
will not have current flow, therefore no braking. Now if I have enough back
EMF (if the RPM is high enough) you would experience one of the adjacent
windings losing effectiveness because the current flow would decrease.

I am curious what you mean by braking mode on a normal stepper.

-----Original Message-----
From: Alan King [mailto:alan@...]
Sent: Friday, August 10, 2001 9:13 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Tawagawa Seiki steppers


Hey,

If that were the case, then braking mode wouldn't work on a normal
stepper either, there isn't anything special about a 5 phase motor for
that case. Two ends of a coil switched to ground brakes, just shorting
the wires you'll feel it, and it also works with two semiconductors
switching to ground. Try it and you'll see, and if what you're thinking
were true, braking wouldn't work for a single seperated motor coil on a
normal stepper either.

Also, on a 5 phase you can *NEVER* (one of the few times you can use
that word and be ok!) consider one coil by itself without then taking
that info, and apply it back through the other coils. Your end going
negative would still not be high impedance, it'd be being pulled up
through that other coil that has it's other side connected to +V. But
it doesn't get the chance to go negative, braking a coil works even with
a seperate coil, so 5 phase or 2 phase doesn't make a difference..



"Scott M. Thomas" wrote:

>
> If you think about it, with 4 coils powered you really don't have one in
> brake mode. Even though both ends of the coils are at the same potential
> (either + or -) the semiconductors on either end can only pass current in
> one direction, therefore which ever direction the back EMF generated on

that

> coil was flowing, one end would be always be in a high impedance state so

no

> braking would occur.
>

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