Specifications

27
PLC and motor
control device
design
The exchange between PLC application and motor control devices is designed using DFB. A DFB (Derived
Function Block) represents a type of starter and it is associated to the type of interface; it is used to manage:
the operating modes: Local buttons and HMI interfaces -
the interface with the starter: Control I/O -
the human/machine interface: HMI interfaces -
the interface with the sequences and the process status: Process control sequence and Status feedback. -
the adjustment of parameters: Param. -
1 Local / buttons
Operating mode selection between Local/Off/Remote selector switch position input (DI).
ARun Runs the motor forward in automatic mode (signal set to 1).
Lock Interlock input for motor operation. Motor operation is stopped or inhibited, when
the input is set to 1. The motor is automatically restarted, when signal returns
to 0 and the run condition is still present (ARun set to 1 in automatic mode or
HMI command set to 1 in manual mode).
ExErr Input for external error signals. Motor operation is stopped or inhibited,
when the input is set to 1. The error has to be acknowledged after it is gone.
Local Sets the block to local mode. The pump is directly piloted by the local button box;
the commands from HMI and process commands are ignored.
Remote The PLC manages the motor. The commands come from a process sequence
in Auto mode and from HMI or SCADA in Manual mode.
2 Process control sequence
This group gathers DFB inputs used by PLC program to control the device, mainly in auto mode.
Note re external errors: signals that prevent or stop device operation. Main difference to the interlock
is that the external error will need to be reset via SCADA/HMI before authorizing a new start of the device.
It is the user's responsibility to dene the error cases that generate a fault.
Local buttons
Local
Remote
Process control
sequence
Control I/O
Param
HMI interface
Arun
FbStat
Param
HMI
FbAuto
FbOff
FbLocal
FbManual
Lock
ExErr
HMI
FbRun
Locked
Error
QCtrl
DFB design
3-Application design
Software design
The general structure of the proposed DFB interface is described below. In order to have clear interfaces,
the same general structure will be applied to all device DFBs.