Re: Speed control

[Bear Woods <bearasaur@yahoo.com>]

Hi.  My name is Aaron.  I have not participated very much to date
(other than to read).  I made an error in calculating density (sea
water and fresh water) in one of my last postings.  I was quite
embarassed that I had made such an error and have been shamed into just
reading for a while.....I especially did not want to cough up my
profession after that!  I am a mechanical (currently design) engineer
in AZ.  These electrical questions are pretty interesting but I do not
have much knowledge to offer there.

At my last job we had large and small equipment that utilized AC motors
and used what were termed 'inverters' for control.  They were pretty
sofisticated (sp?) and I am only familiar with the operational
characteristics but I have often thought that this might be a possible
solution.  The only drawback I could see would be cost and perhaps fall
back control if they were damaged (partial flooding or general
failure).  As I remember they could get pretty spendy.  The ones we
used were Toshiba products.  

Regards,

Aaron

--- Jon Hylands <hylands@ibm.net> wrote:
> On Fri, 14 May 1999 11:43:23 -0500 (CDT), Nathanael
> Henderson
> <jude@pconline.com> wrote:
> 
> >     So, the question to Them That Knows Better is:
>  Is this a good idea, a
> > bad idea, or something else?  Is there an inherent
> flaw in the idea?
> 
> PWM (pulse-width-modulation) is definitely the way
> to do it "right".
> Electric cars all use this.
> 
> The advantages are that at low speeds, you're still
> delivering the full
> amount of voltage to the motor, just not very often,
> so the motor doesn't
> lose anywhere near as much torque as it would if you
> were to vary the
> voltage directly.
> 
> The disadvantage is that a PWM controller costs a
> lot of money (into the
> hundres of dollars).
> 
> Check into the EV (electric vehicle) web pages (a
> good place to start is
>
http://dir.yahoo.com/Recreation/Automotive/Alternative_Fuel_Vehicles/Electric_Vehicles
> 
> Later,
> Jon
> 
> --------------------------------------------------------------
>    Jon Hylands      Jon@huv.com     
> http://www.huv.com/jon
> 
>   Project: Micro Seeker (Micro Autonomous Underwater
> Vehicle)
>            http://www.huv.com
> 

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