Emerson manual WRITING 848L EQUATIONS Basic Motor Control, Rosemount 848L, Reference Manual

Page 80
WRITING 848L

Rosemount 848L

Reference Manual

00809-0100-4696, Rev AA September 2004

Timed Switch

The pumps have a known life time within an acceptable risk, so one pump is allowed to run until that time expires. The other pump automatically takes over at that time.

Switch on Failure

If a process condition can be sensed that says the running pump failed, then the other pump is started regardless of the starting protocol.

WRITING 848L

EQUATIONS

Basic Motor Control

It is not easy to convert a functional diagram to an 848L equation because all of the functions must be nested in the proper order. One way to begin the process is to draw the functional diagram in ladder logic. The following is a basic two button and auxiliary contact motor control that is drawn with channel numbers.

 

 

 

 

1

 

2

 

Out1

+--

--

+--

--

+----------------------

( )--+ OUT1_EQ

 

 

 

3

 

+--

--

+

 

 

 

 

Input 1 is from a normally closed stop button, which does not have to be inverted in the equation. This is true for all stop buttons in the following examples.

Input 2 is from the normally open start button and Input 3 is from the contactor’s auxiliary contact.

The ladder coil shown is at Out1, which is the value of output equation 1. Wires from output 1 will switch power from the control voltage to the contactor’s solenoid or pilot relay.

Since the 848L uses RPN, begin from the lowest line in the ladder diagram and work upwards.

The first expression is OR(IN(2),IN(3)) from “2 or 3” in the ladder diagram. This is one term in an AND function, so build the function around it.

The top and final expression is AND(IN(1),OR(IN(2),IN(3))) from “1 and (2 or 3)” in the ladder diagram.

Enter the expression as the contents of parameter OUT1_EQ in the logic transducer block. Do not forget to append the terminating semicolon.

Connect the buttons, auxiliary contact and contactor (a small relay will do) in order to test the operation.

E-4

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Contents Reference Manual 00809-0100-4696,Rev AA SeptemberRosemount 848L Discrete Logic Temperature Transmitter withRosemount 848L FOUNDATION FieldbusTable of Contents SECTION 1 Introduction SECTION 2 InstallationSECTION 3 Configuration Rosemount 848LSECTION Operation and Maintenance APPENDIX A Reference Data APPENDIX B Product CertificationsAPPENDIX C Function Blocks Rosemount 848LAPPENDIX D Logic Equation Syntax APPENDIX E Motor ControlAPPENDIX F Valve Control Rosemount 848LTOC-4 Rosemount 848LReference Manual SAFETY MESSAGES Warnings SectionIntroduction Rosemount 848LOVERVIEW TransmitterManual Rosemount 848L00809-0100-4696,Rev AA September Rosemount 848LReference Manual Rosemount 848L Reference ManualInstallation SAFETY MESSAGES Warnings MOUNTINGSection Rosemount 848LMounting to a DIN Rail Without an Enclosure Mounting to a Panel with a Junction BoxRosemount 848L Reference ManualMounting to a 2-InchPipe Stand Rosemount 848LReference Manual 00809-0100-4696,Rev AA SeptemberWIRING Power Supply ConnectionsRosemount 848L Reference ManualSWITCHES Surges/TransientsGROUNDING Rosemount 848L00809-0100-4696,Rev AA September Rosemount 848LReference Manual I/O WIRING DISCRETE INPUT WIRING CONFIGURATIONDISCRETE OUTPUT WIRING CONFIGURATION Rosemount 848LReference Manual TAGGINGRosemount 848L INSTALLATION Using Cable Glands TRANSMITTER LABELRosemount 848L Reference ManualReference Manual Using Conduit EntriesRosemount 848L Configuration OVERVIEW SAFETY MESSAGES WarningsSection Rosemount 848LReference Manual GENERAL BLOCK INFORMATION ModesRosemount 848L Reference Manual Link Active Scheduler Block InstantiationRosemount 848L RESOURCE BLOCK FEATURES and FEATURES SEL CapabilitiesRosemount 848L Reference ManualReference Manual MAX NOTIFYRosemount 848L Reference Manual PlantWeb AlarmsRosemount 848L 00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual Reference Manual Alarms I/O TRANSDUCER BLOCKRosemount 848L Reference Manual LOGIC TRANSDUCER BLOCKRosemount 848L Rosemount 848L Reference Manual00809-0100-4696,Rev AA September Figure 3-1.848L Logic Transmitter Data Flow00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual Reference Manual DISCRETE INPUT BLOCKSRosemount 848L DISCRETE OUTPUT BLOCKS MULTIPLE DISCRETE INPUT BLOCKMULTIPLE DISCRETE OUTPUT BLOCK Rosemount 848LRosemount 848L Reference ManualSection 4 Operation and Maintenance FOUNDATION FIELDBUS INFORMATIONSAFETY MESSAGES Warnings Rosemount 848LMAINTENANCE Communication/PowerResetting the Configuration RESTART CommissioningTROUBLESHOOTING I/O Transducer and Logic Block TroubleshootingResource Block NAMUR SensorsRosemount 848L Reference ManualSPECIFICATIONS Functional Specifications Appendix AReference Data Rosemount 848L00809-0100-4696,Rev AA September Rosemount 848LReference Manual 00809-0100-4696,Rev AA September Rosemount 848LReference Manual Physical Specifications Function Blocks SpecificationRosemount 848L Reference ManualReference Manual DIMENSIONAL DRAWINGSRosemount 848L Figure A-3.Rosemount 848L Wiring Diagram Rosemount 848LReference Manual 00809-0100-4696,Rev AA SeptemberReference Manual ORDERING INFORMATIONRosemount 848L Rosemount 848L Reference ManualAppendix B Product Certifications APPROVED MANUFACTURING LOCATIONSEUROPEAN DIRECTIVE INFORMATION HAZARDOUS LOCATIONS CERTIFICATES North American ApprovalsReference Manual European ApprovalsRosemount 848L Appendix C Function Blocks RESOURCE BLOCK PARAMETERSRosemount 848L Reference ManualFREE SPACE Rosemount 848LReference Manual OUTPUT Rosemount 848LReference Manual Reference Manual ADVISE ENABLERosemount 848L I/O TRANSDUCER PARAMETERS Rosemount 848LReference Manual 00809-0100-4696,Rev AA SeptemberTRANSDUCER TYPE Rosemount 848LReference Manual OUT 3 TAG Rosemount 848LReference Manual LOGIC TRANSDUCER PARAMETERS Rosemount 848LReference Manual 00809-0100-4696,Rev AA SeptemberReference Manual DISCRETE INPUT BLOCKRosemount 848L Rosemount 848L Reference Manual00809-0100-4696,Rev AA September Table C-4.ParametersReference Manual DISCRETE OUTPUT BLOCK Supported ModesRosemount 848L Reference Manual MULTIPLE DISCRETE INPUT BLOCKSRosemount 848L Rosemount 848L Reference ManualMULTIPLE DISCRETE OUTPUT BLOCK 00809-0100-4696,Rev AA SeptemberRosemount 848L Reference Manual00809-0100-4696,Rev AA September Table C-7.Parameters andReference Manual Appendix D Logic Equation SyntaxRosemount 848L Rosemount 848L Reference Manual00809-0100-4696,Rev AA September Table D-1.Supported FunctionsPS channel number, divisor Rosemount 848LReference Manual ERROR HANDLING Table D-2.Error HandlingRosemount 848L Reference ManualReference Manual EXAMPLESRosemount 848L Rosemount 848L Reference ManualAppendix E Motor ControlINTRODUCTION TO MOTOR CONTROL Rosemount 848LReference Manual VARIATIONS ON MOTOR CONTROLRosemount 848L 00809-0100-4696,Rev AA September Rosemount 848LReference Manual Reference Manual WRITING 848L EQUATIONS Basic Motor ControlRosemount 848L Reference Manual Interlock Permissive Emergency ShutdownRosemount 848L Reference Manual Restart DelayRosemount 848L Reference Manual Maximum RestartsRosemount 848L Reference Manual Winding TemperatureRosemount 848L Reference Manual Hand-Off-AutoRosemount 848L Reference Manual Intermediate StopRosemount 848L Reference Manual Redundant Motors - Alternate StartRosemount 848L Reference Manual Redundant Motors - Timed SwitchRosemount 848L 00809-0100-4696,Rev AA September Rosemount 848LReference Manual Reference Manual Redundant Motors - Switch on FailureRosemount 848L 00809-0100-4696,Rev AA September Rosemount 848LReference Manual E-16 Rosemount 848LReference Manual Appendix F Valve ControlINTRODUCTION TO VALVE CONTROL Rosemount 848LReference Manual Alarms Variations on Valve ControlRosemount 848L Reference Manual Boolean Expressions Basic Valve ControlRosemount 848L Open-Auto-Close Alarm Variations Output Variations Output with InterlockRosemount 848L Reference ManualReference Manual Simple Valve Variations PermissiveRosemount 848L Reference Manual Double Block and BleedRosemount 848L Reference Manual Motorized Valve Heat Exchange Medium SelectionRosemount 848L Rosemount 848L Reference ManualIndex Rosemount 848LReference Manual 00809-0100-4696,Rev AA 9/17/0400809-0100-4696,Rev AA 9/17/04 Rosemount 848LReference Manual 00809-0100-4696,Rev AA 9/17/04 Rosemount 848LReference Manual Index-4 Rosemount 848LReference Manual ¢00809-0100-4697F¤ Reference Manual