Programming Advice

[Splash 0]

Have a project using a CPU-226 thats starts groups of motors after a power blip. I am wanting to start groups of motors in categories after loss of power to the MCC. The 226 has a run input and start output for each motor, as well as an undervoltage input for loss of power. The plc is being powered by a UPS. I am looking for ideas as to how to "capture" motors running before the power blip so they can be started after powered is restored.

[Henric 0]

every time a motor changes it state and you have power (running to not running or vice versa) save the motors status to a word or doubleword. example motor 1running motor 3 running rest of = 0000 0000 0000 0101 when power comes back you compare bit for bit with corresponding motor and start them if they had status 1 before.. do you get it??

[Crossbow 295]

It's been a while since I worked on an S7-200, but they should have some memory retentive addresses, which will not lose their status if the power goes out. Not sure if this will help since you did say the PLC is on a UPS. But the idea to copy the outputs to a word and use the bits in that word make perfect sense.

[Splash 0]

Makes since, the other problem i think i may have is determing if the motor was stopped intentionally or was it stopped because of undervoltage. I'm thinking i am gonna have to use a timer for each motor, if i get a stop and dont get an undervoltage within a certain amount of time, then its a planned stop else it was an undervoltage stop and go ahead restart once power is back.

[Crossbow 295]

Are these motors running on variable speed drives? Most drives include an alarm output which can be brought back to the PLC and tell you when an alarm (like undervoltage) occurs in the drive.

[Splash 0]

They're all cutler hammer advantage starters. We are probaly gonna set the undervoltage relay to pickup just before the threshold of the coil on the starters to sort of "predict" a bower blip.