Re: [CAD_CAM_EDM_DRO] Gecko G420's question

The rumor started from Mariss's recent post: "ITs ALIVE"

Tom

----- Original Message -----
From: "Nicolas Benezan" <bene@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, April 30, 2002 5:35 AM
Subject: Re: [CAD_CAM_EDM_DRO] Gecko G420's question


> David Eldredge wrote:
> >
> > Does anyone know what type of feedback the G420's are expected to use?
> > Hall effect or encoder?
>
> Where did you get information about the G420? I heared roumors, too. But
> there's no announcment or other info on their web page. Do you know when
> they will be available.
> (I'm new to this list)
>
> I know brushless motors from Indramat (german company). They use both,
> hall effect sensors for the commutation (6 pulses per rev) and optical
> encoders (2500 p/rev) for the feedback loop.
>
> Someone said, the brushless geckos will have the same voltage and
> current rating as the others (80V 20A). But most brushless motors
> available here in Europe are 600V-types (directly fed from 400V mains
> without transformer). Are there any sources for 60-80V brushless motors?
>
> > Will the G420s save money on servo motor cost? I understand the
benefits
> > of eliminating brushes and commutators, but are there many sources of
> > motors for them?
>
> Probably more than for servo motors with brushes. In new proffessional
> machines, you find exceptionally brushless motors. None of the "big"
> manufacturers i know still uses brushes.
>
> > Someone mentioned that the brushless motor is kind of like a DC
permanent
> > motor turned inside out, I think.
>
> Yes, a brushless motor is mainly a synchronous AC motor with the coils
> in the stator and a permanent magnet in the rotor.
>
> > Can someone take a three phase AC motor, and make a new rotor with
permanent
> > magnets glued to the rotor and make their own motors?
>
> Yes this would work, although it is difficult to create the proper
> "shape" (sinusodial or trapezoid) of the magnetic field like this. If
> the waveform of the voltage of the motor (when used as generator)
> doesn't match that of the driver/commutator you will have a lot of
> torque ripple.
>
> I tried to build something similar to the geckos for brushless motors
> myself a few years ago but effectively gave up due to the torque ripple
> problem. It is not sufficient to simply switch the coils in a constant
> relation to the shaft angle the way you do with a stepper motor. You
> either have to add speed dependant phase shift or drive the current in
> some continous shaped (sinusodial or smoothened trapezoid) way which is
> not that easy.
>
> > Maybe a dumb question,
> > but I thought I'd ask. I have re-glued permanent magnets back on some
motor
> > housings in the past. They seem simple enough.
>
> Yes, theoretically it would work if you could get magnets that fit. You
> could even mount a solid ring of permanent magnetic material on the
> shaft and use the coils of the motor itself to magnetize the rotor with
> a very high current pulse. But I doubt that this results in a high
> quality motor.
>
> Ciao
> Bene
>
> --
> !!! Achtung, neue Adresse !!!
> Benezan Electronics, Maria-Merian-Str. 20a, 70736 Fellbach, Germany
> Kundenspezifische Elektronikentwicklung, Sondermaschinenbau
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