Newsgroups: comp.robotics
Path: brunix!uunet!haven.umd.edu!darwin.sura.net!uvaarpa!cv3.cv.nrao.edu!cv3.cv.nrao.edu!browen
From: browen@lyapunov.aoc.nrao.edu (Bruce Rowen)
Subject: Re: looking for a SCR speed control unit....
In-Reply-To: hattori@csrd.nkk.co.JP's message of Mon, 28 Jun 1993 04: 11:05 GMT
Message-ID: <BROWEN.93Jun28123857@lyapunov.aoc.nrao.edu>
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Organization: National Radio Astronomy Observatory, Socorro NM
References: <HATTORI.93Jun24102855@athena.csrd.nkk.co.JP>
	<20b6jeINNfdn@master.cs.rose-hulman.edu>
	<1993Jun25.144520.24601@nrcnet0.nrc.ca>
	<HATTORI.93Jun28131105@athena.csrd.nkk.co.JP>
Date: Mon, 28 Jun 1993 17:38:57 GMT
Lines: 30


In article <1993Jun25.144520.24601@nrcnet0.nrc.ca> ORBAN@amt00.ime.nrc.ca (Peter Orban) writes:

 |SCRs are also used for controlling the speed of DC motors. The SCRs
 |form a rectifying bridge (usually three phase) and the turn on
 |time is controlled. Like your dimmer at home. SCR drive units got
 |superseeded by the PWM and most recently by AC drives, as those 
 |have higher bandwidth. (SCR units work with 50 or 60 Hz, depending 
 |where you are, while PWM units have the switching frequency in the 
 |KHz range.) SCR units are still used where high bandwidth is not a
 |criteria, as they are a lot cheaper.

>I didn't know SCR can be used for DC control.  I need to study more
>about SCR...  Thank you Peter.  
>
>As you said, using SCR rather than FET is much reasonable when we try
>to control BIG motors, like RC car's one.  Usually, RC car's motors
>are so highly tuned, because higher speed gives us much more fun, that
>more than 30 Amperes of DC current flows in control circuit.  It's
>hard to find a FET with such big capacity.
                ^^^^^^^^^^^^^^^^^^^^^^^^^
FETs of several hundred amps are easy to find!
they have a great speed advantage (efficient) over SCR's that make
them the ideal choice if you feed and care for them properly.

>--
>Mato  Hattori                      Computer System Research Department,


BR
