3
Inverter Control with Process Data
By
Process Data (PD) we mean all time-critical (real time) data in a process which have to be
processed or transferred at high speed. These data are characterized by the fact that they are highly
dynamic and always up to date. Examples of process data are setpoints and actual values of the
inverter, or peripheral conditions of limit switches. They are exchanged in cycles between the
automation unit and the inverter.
Control of the MOVITRAC
®
31.. inverter by means of process data takes place on the fieldbus system.
The process data interfaces for
Process Input (PI) and Process Output (PO) should be treated
separately. Process input data (PI) are data that are transmitted from the inverter to the higher-level
automation unit (e.g. status information, actual values, etc.). Process output data (PO) are data that
are output to the inverter by the automation unit (e.g. setpoints, control commands, etc.).
3.1
Commissioning the Inverter
Parameters can be assigned to the MOVITRAC
®
31.. inverter via the fieldbus system immediately
after the fieldbus option pcb has been installed; no further settings are necessary. Amongst other
things, this enables all parameters directly to be downloaded from the higher-level automation unit
via the fieldbus system after switching on the inverter.
To control the inverter via the fieldbus system, however, the latter must first be switched to the
relevant control mode. This can be done with the parameter
P841 Control Mode. After the inverter is
set to the factory settings, this parameter is set to
STANDARD (control and setpoint processing via
input terminals). The inverter is parameterized to accept the setpoints from the fieldbus with the
setting
P841 Control Mode = FIELDBUS. The MOVITRAC
®
31.. will now react to the process output
data transmitted by the higher-level automation unit.
Activation of the fieldbus control mode is signalled to the higher-level control by means of the
Fieldbus
Mode Active bit in the status word.
For safety reasons, the inverter must also be enabled on the terminal side in order for it to be controlled
via the fieldbus system. The terminals should therefore be wired or programmed so that the inverter
is enabled via the input terminals. The simplest method of enabling the inverter via the terminals is
to provide input terminal 41 (
CW/STOP function) with a +24 V signal and to program input terminals
42 and 43 to
NO FUNCTION. Fig. 1 demonstrates how the MOVITRAC
®
31.. inverter is commissioned
with a fieldbus connection.
Attention!
Carry out commissioning with mains voltage switched off and with the external 24 V-supply only.
This prevents the drive from starting to move automatically during reprogramming. Switch on mains
voltage only after completed setting of parameters.
3
Inverter Control
with Process Data
MOVITRAC
®
31.. Fieldbus Unit Profile
9
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