ABB ACH 501 - Page 99

Chapter 6 – Parameters
ACH 500 Programming Manual 6-53
Figure 6-23 show three examples of actual value scaling.
Figure 6-23 Actual Value Scaling
27 ACT 2 MIN SCALE Refer to Parameter 40.2.25.
28 ACT 2 MAX SCALE Refer to Parameter 40.2.26.
29 BYPASS CONTROL NO/YES
The PI regulator of the PFC can be bypassed if the value of Parameter 40.2.29
is set to YES. When the regulator is bypassed, the actual value signal replaces
the output of the PI regulator as a final speed reference. The automatic start
and stop of constant speed motors is referred to the actual value signal instead
of the output of the PI regulator. Refer to Figure 6-24 for an example of the PI
regulator bypass function. This function is useful in flow control of
precipitation tanks.
Figure 6-24 PI Regulator Bypass Function
10 V(100%)
8 V(75%)
4 V(25%)
2 V(0%)
0 V 0%
100%
Actual Scaled Actual
10 V(100%)
8 V(80%)
4 V(40%)
0 V(0%) 0%
100%
Actual Scaled Actual
100%
60%
20%
0% 0%
100%
Actual Scaled Actual
Minimum AI 2V/4mA
Act 1 Max Scale 75%
Act 1 Min Scale 25%
Minimum AI 0V/0mA
Act 1 Max Scale 80%
Act 1 Min Scale 40%
Act 1 Max Scale = 20%
Act 1 Min Scale = 60%
Frequency = f(ACT 1)
f
max
f
min
H
min
H
max
Level of a Tank
RUN
STOP
RUN
STOP
Regulated Pump
1. Aux. Pump