On Wed, 8 Oct 2008 09:13:35 -0700 (PDT), Vernon
wrote:
On Oct 8, 10:02*am, "Pete C." wrote:
"DoN. Nichols" wrote:

The best course is to follow the e-stop wiring guides provided in the
VFD manual.

Thanks. But is "e-stop" the same as "dynamic braking"? The latter
term is the only thing I see in the glossary.

D: All of the Above.

A true "Emergency Stop" button is: "Cut the main motor power and
trigger the dynamic braking, ignore all other inputs saying Start or
Run while the E-Stop circuit is open, dump or short out the main power
input if you have to, damage the drive by blowing the main SCR's if
you must, shove a chock block into the gears - but whatever you need
to do to make it happen YOU WILL STOP NOW, PERIOD."

In the old days, they would place a huge contactor as a "Crowbar
Safety" so it puts a dead short across the main motor power line, to
blow the main fuses upstream if the service motor contactor welds shut
or gets mechanically stuck and won't open.

Or they put two magnetic contactors in series, one for service and
one for emergencies only, on the theory that two of them won't both
have welded contacts at the same time.

But you only went to that much trouble on things like punch presses,
where people crawl inside to service it and/or they stick their hands
inside the open jaws to load material and remove the finished goods.
And the edict has been issued that This Machine Shall Not Start Up
Unexpectedly, nor fail to shut down when turned off.

-- Bruce --