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4. OPERATING MODES
4.6
Closed Loop Control
4.6.1
General Description
The MICROMASTER provides a PI control function for closed loop control (see Figure 4.6.1). PI control is
ideal for temperature or pressure control, or other applications where the controlled variable changes slowly or
where transient errors are not critical. This control loop is not suitable for use in systems where fast response
times are required.
When closed loop PI control is enabled (P201 = 002), all setpoints are calibrated between zero and 100%, i.e.
a setpoint of 50.0 = 50%. This allows general purpose control of any process variable that is actuated by motor
speed and for which a suitable transducer is available.
Set point input
MICROMASTER Closed loop PI control - Block Diagram
Figure 4.6.1
4.6.2
Hardware Setup
Connect the outputs from the external feedback transducer to control terminals 3 and 4. This analogue input
accepts a 0/2 - 10 V signal, has 10-bit resolution and permits a differential (floating) voltage. Ensure that the
values of parameters P023 and P024 are set to 000 and that P006 is set to 000 or 002.
15 V dc/Max 50mA power for the feedback transducer can be supplied from terminals 8 and 9 on the control block.
4.6.3
Parameter Settings
Closed loop control cannot be used unless P201 is first set to 002. Most of the parameters associated with
closed loop control are shown in Figure 4.6.1. Other parameters which are also associated with closed loop
control are as follows:
P001 (value = 007)
P061 (value = 012 or 013)
P210
P220
Descriptions of all closed loop control parameters are provided in section 5. For further detailed information
about PI operation refer to the application note "Closed Loop Control", which may be obtained from
http://www.con.siemens.co.uk, or a Siemens sales office..
© Siemens plc 1999
Proportional
Gain
P202
Integral
Integral
capture
Gain
P207
P203
Closed Loop
Transducer
Control on/off
Type
P201
P208
MICROMASTER
Ramp rates,
P002, P003
Scaling
Sample
P211
Interval
P212
P205
23
Motor
Process
Filter
/Integrator
P206
G85139-H1750-U049-C1
English
19/08/99
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