Re: [CAD_CAM_EDM_DRO] Re: What makes a motor a servo? calculating power

----- Original Message -----
From: "Codesuidae" <codesuidae@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, May 11, 2005 2:29 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: What makes a motor a servo? calculating
power


> Mariss Freimanis wrote:
>
> >I figure on about $35 per lb for motors. Check it out:
> >
> >1) USDigital MS-23 single-stack 23, 1.6 Lbs, $59
> >2) Vexta PK268 double-stack 23, 2.25 Lbs, $80
> >3) Camtronics IH34-112 double-stack 34, 5 Lbs, $165
> >4) Machine Tool Camp 34-size servo, 10 Lbs, $350
> >
> >It makes sense. The motor market is competetive, profit margins are
> >small. The ingredients for the product are primarily copper, iron and
> >aluminum, commodities that are priced by weight.
> >
> >
> If only hobby RC motors for cars and airplanes were similarly priced.
> In their case the price depends mostly on how cool the stickers on the
> case look. :)
>
> I'm curious about brushless motors. They are built somewhat like
> steppers, but operate more like servos. The brushless motors I'm
> familiar with from RC cars typically consist of a 4 pole rare earth
> magnet mounted on the shaft, with three coils in wye configuration
> (evidently delta configuration is preferred for motors that don't
> normally run in one direction) and connected to a brushless controller.
> The motor may or may not have magnetic or optical feedback sensors.
> These motors typically have horrendous cogging as they are intended to
> run at high speed.
>
> Steppers seem to be essentially the same kind of beast, magnet rotor
> with a smart controller running some coils to make the magnets chase a
> rotating field around (or stand still in the same place). And yet while
> brushless servos are smaller, lighter, more powerful and more efficent
> than brushed servos, steppers are slower, bulkier, weaker and less
efficent.
>
> What is it about the design differences that make brushless servos good
> for high speed, high power applications (everything from RC toys to
> electric cars for example), and take steppers in the opposite direction?
>
> cs
>
>
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