2271SVC 440 795 M01006 Inside the logic relayLogic relaycircuit diagram cycleIn conventional control systems, a relay or contactor controlprocesses all the rungs in parallel. The speed with which acontactor switches in this case depends on the componentsused, and ranges from 15 to 40 ms for relay pick-up anddrop-out.With the circuit diagram the logic relay is processed with amicroprocessor that simulates the contacts and relays of thecircuit concerned and thus processes all switchingoperations considerably faster. Depending on its size, the CLcircuit diagram is processed cyclically every 2 to 40 ms.During this time, the logic relay passes through fivesegments in succession.How the logic relay evaluates the circuit diagram:In the first three segments the logic relay evaluates thecontact fields in succession. The logic relay checks whethercontacts are switched in parallel or in series and saves theswitching states of all contact fields.In the fourth segment, the logic relay assigns the newswitching states to all the coils in one pass.Rungs Segment1 2 3 4 51234…I1-q1-j--ÄQ8I1-I4-Ö1-TT2I2-I3----RT2T2-u-----ÄQ1P1-kêê êêê
