Hi,
I'm new so bare with me if I do something wrong here. Well the problem, I hooked up a micrologix 1000 to switch a lathe between forward and reverse. The lathe started out a 3 phase 7hp motor which was switched to a 240 single phase 7hp motor.
It works fine most of the time but I'm not sure if when I stop or start the motor sometimes the processor will fault with a major error 8h "A fatal internal software error occurred."
The plc is mounted in the same panel as the motor starter relays and 240ac input lines. Seems to be caused from inconsistant ac supply to the plc when lathe is stopped or started.
What do you guys think my problem is, like I said I think it is happening when lathe is stopped because I don't hear the motor relays try to start when it happens but works fine until the stop switch is pushed.

The controller is a 1761-L16BWA

Thanks in advance,
Tom

Yep, I agree, it's most likely "dirty" power supply.

If you have room for a small PC sized UPS, hook the current power feed for the PLC into the UPS, and then take the UPS output to the PLC, should condition the power, and give a few minutes of runtime when the power goes low or off.

If you don't have room to permanently mount the ups, you could still try it on a temporary basis, this will confirm your theory.

Ken

Glitches are getting in.. I'm pretty sure that's the problem because it happens during switching. As the earlier poster said you could use a UPS, but often a line filter like a control concepts Islatrol is fine. Uses much less panel space too :) I hear the Corcom filters do a decent job as well.

Even if you have the line power filtered, you could still have glitches coming in from the inputs or outputs. Do you have suppressors on ALL coils? Valve solenoids, motor starters, control relays, etc. Everything well grounded? High voltage and low voltage wiring NOT runnning in parallel?

Micrologix's are nice processors, but are *VERY* sensitive to spikes, glitches, and power fluctuations. I get minor faults or lost programs all the time on uL1000-equipped machines we've got here.. Most of which were not properly built. Doing a good job with a micrologix "separates the men from the boys", so to speak.


The following Technote is written for SLCs, but applies equally well for micrologix or ANY control system for that matter:


http://domino.automation.rockwell.com/appl...6A?OpenDocument

Thanks for the replys guys, yes I do have suppressors across the coils of the motor starters. Hi and low voltages do not run in parallel to each other. I've installed many micrologix systems but never in a lathe switching a large 7hp single phase motor.
I did aquire a Corcom EMI filter that will be tryed this weekend.
A battery backup next if this doesn't help.
Tom