Need Help with Medar 3005 and SLC 5/03

[chas183 0]

Hello, I need a point in the right direction. I have a medar card software version T93300-00-20 and an allen bradley SLC 5/03. I added a cascade card to the system and now I get shorted WCU#00 and Breaker tripped. I only get the fault if the isolation contactor is closed and I have no SCR selected. How can I get around this? I want to have the isolation contactor closed during a machine cycle and select the SCR and weld schedule as needed during machine cycle. It would apper that the Medar card wants voltage signal when ever the contactor is closed and the scr is selected. If the contactor comes in and no scr is selected I get the faults. If I hold the SCR high until the contactor goes low I have no problems. I do no not want to cycle the contactor in and out every weld but want to have it closed for 15 seconds. If the machine cycles within the 15 seconds the contactor stays closed. I have attached the program for review. Please keep in mind that this is a work in progress. The current ladder file I am working on is ladder 4 LH Function. Kindest Regards, Charlie WP IN HOUSE 8-3-10.RSS

[Armadillo852 25]

Why not just use the contactor saver option in the Medar? You should be able to select the scr, but just not initiate the weld. Edited 5 Aug 2010 by Armadillo852

[chas183 0]

Thanks for the help. I made a work around by always keeping SCR 1 high while the contactor is in. If SCR 2 is called SCR1 goes low. Kindest regards, Charlie

[jholmes 0]

In reply to this post, I had recently run into a similar issue and had a medar tech visit on site. He installed a simple hardwire jumper between the scr3 input and +24v, this will eliminate a shunt fault that occurs on the pendant when switching scr wires (the medar is faster than the plc can deenergize and energize outputs) The way it was explained was scr2 input overrides scr3; scr1 overrides scr2 and scr3.. We can leave scr3 on all the time because it will be overridden if required. The other alternative is if you have the medar processor in your allen bradley rack you can use the software bits to trigger the scr... Excerpt from the integrators manual: B6x:11/02-05 Locations 02, 03, 04 and 05 define the Contactor Select Bit #1, #2, #4 and #8, respectively. The user decodes the Contactor select bits to control separate contactor outputs (1 to 15). These bits are provided by application programs that support multi-contactor operation. Currently these are T93300–17 or greater, and T93302–03 or greater.