Re: E-stop relay welds contacts for load dump resistor

Correct about the multi-pole relay. I am using a 4 pole, DT relay that is set to "latch" when E-stop is released. On E-stop press, one set of NO contacts opens the AC to the Toroid, while a second set of NC contacts crowbars the resistor to ground, to bleed the stored energy from the power supply filter capacitor. Of course, when the contacts for the load dump resistor stuck in the closed position, the exact situation you described did occur, burning up the resistor after a minute or two. The other two contacts of the relay are to signal the Hitachi VFD and the computer that E-stop has occurred. I am using the exact E-stop circuit design recommended by Geckodrive as shown at the bottom of this page:

http://finance.groups.yahoo.com/group/geckodrive/files/G320%20and%20G340/

The file is called "Servo E-stop circuit" and by reading Mariss' description, it is the recommended way to implement E-stop, without risking damage to the G320 drives. Jon Elson commented earlier that he saw some shortcomings in this circuit, but it looks like an old circuit design that has been around for more than 5 years and there are probably lots of people using this same circuit. That is the part that puzzles me, that it must work OK or it would not be published any longer. Thanks for all the help!

Dan.
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--- In CAD_CAM_EDM_DRO@yahoogroups.com, "David G. LeVine" <dlevine@...> wrote:
>
> On 01/30/2011 02:48 PM, kzf817 wrote:
> > + Terminal on power supply Cap---> 7 ohm resistor--->
>
> I did not see where there was an interlock on the power supply to
> protect the resistor against the power supply against the ESTOP
> crowbarring the output. You need one or the 7 ohm resistor must be
> better than 1/2 KW!
>
> Consider a DPDT relay. When energized (I.E. no ESTOP), it allows AC to
> flow into the supply and is open in the resistor path. When deenergized
> (i.e. ESTOP or power failure), it opens the AC input to the supply and
> shorts the 7 Ohm resistor to ground.
>