how does this plc programme work?

[ant9985]

Can someone tell me how this PLC programme works please?
You will have to use the zoom in option to see it properly

 

[Skogsgurra]

Looks like some sort of a controller application for crane application wound induction motor. Probably a motor for raising/lowering an arm (or some other heavy part) since there is no reverse, which implies that the load always tries to bring the load back down. Or simply a starter circuit for a high inertia load.

The X-es are probably input from the operator stick and the R-s are probably outputs that control the contactors. R1 - R6 are probably the "step" contactors that short out the rotor resistors. T1-T5 seem to be there to prevent too fast acceleration, making it impossible to short out the whole rotor resistor in less than 25 seconds (all T-s have a 5 second delay).

The R0 contacts seem to be MR contacts that keep the whole thing up and running as long as X0 AND X11 are activated.

Lots of reservations on this one. Unusual to see an application with no NC contacts. Also wonder what X0/X12/X1 are doing there. An alternative command path?

 

[ant9985]

im not really sure, im kind of new to plc programmes, thnx a lot for the help