Re: Big servo motors drive recommendations

Mark -

You have shared some interesting observations. You mentioned that
your motors were about 1 ohm resistance. Do you know the inductance?
The PWM drives usually have a minimum inductance specification that
will work with the PWM rate. In an earlier post you described that
the PWM was "folding back" on one of the drives you tested at large
PWM ratios and that makes me wonder if the issue has more to do with
the PWM response in individual PWM cycles than with the PID algorithm
itself. Ideally the PWM cycle rate is fast compared to the current
rise time in the motor windings such that the motor current during a
move would change over multiple cycles and not hit the trip limit
within a cycle. If you are hitting the drives current limit during
hard acceleration and over several PWM cycles, then this would
probably not be the case. It is an interesting issue; thanks for the
post.

Regards,
Gary

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mark Vaughan" <mark@...> wrote:
>
> I'll second that.
>
>
>
> Dr. Mark Vaughan Ph'D. B.Eng. M0VAU
>
> Managing Director
>
> Vaughan Industries Ltd, reg in UK no 2561068
>
> Water Care Technology Ltd, reg in UK no 4129351
>
> Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
> Phone/Fax 44 1872 561288
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> RSGB DRM111(Cornwall)
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> _____
>
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Steve Blackmore
> Sent: 27 May 2007 16:33
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Re: Big servo motors drive
recommendations
>
>
>
> On Sun, 27 May 2007 13:27:21 +0200, you wrote:
>
> >Well, time is money and money is time. If converting is sucha a
pita ill
> hold on
> >to this machine a year longer bleeding $$$ for repairs and then buy
a new
> or
> >fairly new instead of messing for countless hours to convert it into
> something
> >slow and sensitive. Rapids in my machine are 12000mm/s, 10000mm/s and
> >7000mm/s. And I need to be able to cut in 400mm/s.
>
> Yep - Often when you take into account all the messing around with time
> and "cheap" parts, you could have gone out and bought commercial parts
> or even a good second hand machine for less...
>
> Steve Blackmore
> --
>
>
>
>
>
> [Non-text portions of this message have been removed]
>