Newsgroups: comp.robotics
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From: hattori@csrd.nkk.co.JP (Mato Hattori)
Subject: Re: looking for a SCR speed control unit....
In-Reply-To: ORBAN@amt00.ime.nrc.ca's message of Fri, 25 Jun 93 14:45:20 GMT
Message-ID: <HATTORI.93Jun28131105@athena.csrd.nkk.co.JP>
Sender: news@csrd.nkk.co.jp
Organization: Computer System Research Dept., Elec. R. Center, NKK Corporation,
	Kawasaki, JAPAN
References: <HATTORI.93Jun24102855@athena.csrd.nkk.co.JP>
	<20b6jeINNfdn@master.cs.rose-hulman.edu>
	<1993Jun25.144520.24601@nrcnet0.nrc.ca>
Date: Mon, 28 Jun 1993 04:11:05 GMT
Lines: 25

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.
---
--
Mato  Hattori                      Computer System Research Department,
email : hattori@csrd.nkk.co.jp     Electronics Research Center, NKK Corporation
voice : 81+44-322-6281 (office)    1-1 Minamiwatarida Kawasaki-ku
      : 81+44-246-9665 (home)      Kawasaki-city, 210 JAPAN
