RE: [CAD_CAM_EDM_DRO] resistor for power supply

What your friend says is strictly true.
However as long as the ratings on all components is high enough you
don't need the resistor unless you are trying to limit start up current.
Even if you are trying to limit start up current usually I would use an
inrush limiter that effectively goes to 0 ohms once the cap is charged
(In other words effectively becomes a piece of wire) not a resistor as
this will effect the voltage depending on load conditions.

Chris.

-----Original Message-----
From: cadcamcenter [mailto:cadcamcenter@...]
Sent: Monday, December 10, 2001 4:53 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] resistor for power supply


Hi all,

So far all the suggestions for the power supply for drives shows the
connection from the output of the bridge rectifier direct to the
capacitor (some may have bleed resistor, LED etc in parallel)

An power engineer (who may not have very much experience with CNC
items) mentioned that there will a large current surge on initial
power up (when V on cap is 0) and suggested putting a resistor. My
interpretation of his suggestion

rectifier R
. .-----/\/\/\-----
/ \ |
/ \ _____
/ \ _____ C
\ / |
\ / |
. \./---------------

What does the list think? And if this is an improvement what kind of
relationship R = function (C,I,etc) should there be between R, C etc.

A million thanks to the list

Peter




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