On 09/17/2010 09:21 AM, Karl Townsend wrote:
On Fri, 17 Sep 2010 07:06:25 -0700 (PDT), Jim Wilkins
wrote:
On Sep 17, 9:51 am, Jim wrote:
...
Digikey lists rectifiers up to 400A
http://search.digikey.com/scripts/DkSearch/dksus.dll
The anode/cathode studs let you use only two heatsinks.
jsw
That copied URL didn't lead to the part, so search for DSA75-16B and
DSAI75-16B.
jsw
Thanks, these parts are diodes. One is an anode stud, the other a
cathode stud. Do I need two of each? Draw me a picture of how to make
these parts into a bridge rectifier, please. (I'm thinking each AC
line gets one of each with both cathodes on one block and both anodes
on the other.) Does a cathode or an anode stud go to ground?
Do I tap these into an AL block for heat shink ? For my "hot" bock
could I also tap cap connections and four spots to send power to the
four servo amps? I would plan to fuse each servo here.
.--|-----.
| |
| |
-. ,----o--)--|-----o--o-----o VDC+
AC in )|( | | |
)|( | | |
-' '----)--o--|---. ---
| | ---
| | |
'-----|---o----o-----o VDC-
(created by AACircuit v1.28.6 beta 04/19/05
www.tech-chat.de)
The "VDC-" here is probably what you want to use for ground. You can
see how two anode-stud and two cathode-stud rectifiers would simplify
the heat sinking.
Usually you see these bolted to a heat sink -- the heat sink has a
through hole, with a bolt on the back. You could tap the heat sink, but
then you'd have to be sure to put the rectifier in before soldering, and
unsolder it before removing if you ever have to replace it. I'd prefer
working on a piece of equipment that's design such that I can take the
diode loose easily without unsoldering -- so, easy access to both sides
with wrenches, and a bolt-on diode.
Your idea of using the heat sink as a terminal block has merit, as long
as you pay attention to aluminum's deficiencies as an electrical contact
material. Check the data sheets -- if you need to use copper heat
spreaders anyway you can use those for your electrical termination. Or
just use some thin copper for a conductor, and only use the aluminum for
heat conduction.
Use all due caution in protecting innocent bystanders from the high
voltage, of course.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at
http://www.wescottdesign.com/actfes/actfes.html