Siemens 6SE2101-1AA01, Operating Manual

Page: 34 / 110

English 6/1

Siemens plc 1993
6. USING CLOSED LOOP SPEED CONTROL
6.1 Introduction
Closed loop speed control ( see Figure 6) allows the speed of a motor to be regulated to hold constant the analogue
value of a speed measuring device (e.g. a tachometer) for a given ‘requested frequency’ setting of the inverter.
The actual speed signal must be positive and in the range 0 – 50 V.
f
t
fmax – P08
fmin – P07
Ramp Generator
Requested
Frequency
Scaling
Actual
Speed
Factor
P31
Sampling Rate P36
f
Slip Limit
Speed Controller
P32, P33, P34
P35
Actual Frequency
P37
+
–
Figure 6: Closed Loop Speed Control
Motor
Tachometer
(0 – 50 V
max
)
6.2 Installation of Control Loop Speed Control
6.2.1 Scaling Factor of ‘Actual Speed’
The actual speed signal is connected to terminal X11.12 (positive) and X11.10 (negative / 0 V). The appropriate
voltage from the actual speed measuring device is to be calculated at f
max
. If the voltage can exceed 50 V at
maximum frequency, an external scaling resistor is required. This can be calculated using the following formula:
R
ext
= 50 k
Ω
x –1
V
max
50
( )
The scaling of the analogue value of the feedback signal can be adjusted with P31. This can be achieved as
follows:
(1) Operate the inverter with the following parameter settings:
P30 = 001 Speed control enabled
P31 = 00.1 Scaling factor
P32 = 001 Speed regulator proportional gain term
P33 = 000 Speed regulator integral gain term
P34 = 000 Speed regulator differential gain term
P35 = 00.0 Slip limit
Ensure that the maximum frequency parameter P08 is set to the correct value for the application.
Initially set P09 to the same value as P08 and set P04 to 003.
(2) Run the inverter. The motor speed will increase until the value stored in P08/P09 is reached.
(3) With the inverter running at maximum frequency, look at the value of parameter P37 (actual
frequency). Adjust the value of parameter P31 (scaling factor) until the value of P37 corresponds
to the maximum frequency P08.