Using Closed Loop Speed Control; Introduction; Installation Of Control Loop Speed Control; Scaling Factor Of 'Actual Speed - Siemens Simovert P 6SE21 Series Operating Instructions Manual

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SIMOVERT P 6SE21 Series Inverters

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.
fmin – P07
Requested
Frequency
fmax – P08
Actual
Speed
(0 – 50 V )
max
Figure 6: Closed Loop Speed Control

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
frequency, an external scaling resistor is required. This can be calculated using the following formula:
(
R = 50 kΩ x
ext
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
P31 = 00.1
P32 = 001
P33 = 000
P34 = 000
P35 = 00.0
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.
32
G85139–A1615–U156–A
02.95
f
t
Ramp Generator
Scaling
Factor
P31
Sampling Rate P36
)
V
max
–1
50
Speed control enabled
Scaling factor
Speed regulator proportional gain term
Speed regulator integral gain term
Speed regulator differential gain term
Slip limit
Operating Instructions
Slip Limit
+
–
f
Speed Controller
P32, P33, P34
Actual Frequency
P37
. If the voltage can exceed 50 V at maximum
max
Motor
P35
Tachometer
Siemens plc 1995