Siemens G85139 Closed Loop Control, General Description, Hardware Setup, Parameter Settings

4. OPERATING MODES English

4.6 Closed Loop Control

4.6.1 General Description

The MICROMASTER provides a PI control function for closed loop control (see Figure 11). 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.

Note: The closed loop function is not designed for speed control, but can be used for this provided that fast response times are not 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.

Setpoint

Low Pass
Filter	Scaling
	–
P206	P211, P212

Feedback

Sample

Rate

P205

P	Acceleration/
P202	Deceleration
+	Ramp	Motor
		M	Process
			e.g. fan
	P002, P003		Feedback
		(e.g. duct pressure)
I			Transducer

P203, P207

P208

Closed Loop Mode Disabled
P201 = 000
Closed Loop Mode Enabled	Feedback
	Monitor
P201 = 002	P210

Figure 11: Closed Loop Control

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 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 11. 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 Siemens DA 64 Catalogue.

© Siemens plc 1997G85139-H1750-U049-B

19 26/09/97