Hitachi SJ 300 - Manual (Page 4)

SJ100/L100 / PID / 4
SJ100/L100 series inverters have integrated PID control, which is indicated by the dotted line in Fig. 2-1.
You can use PID control by setting a target value and providing a feedback signal.
The example in Fig. 2-2 shows a connection diagram for ventilation flow control in a fan application.
(1) P : Proportional Control
This controls the output frequency so that output frequency and deviation have a proportional relation.
The coefficient of deviation and output frequency (expressed in %) is called Proportional Gain (K
p
). This
parameter can be set under function [A71].
Fig. 2-3 shows the relationship between deviation and output frequency. If you set a high value of K
p
,
the response of the system to a rapid change in deviation is fast. However, if K
p
is too high, the system
can become unstable.
SJ100/
L100 Target
Feedback
Transducer
(DC0-10V, 4-20mA)
Flow volume sensor
Fan
Motor
Fig. 2-2 Wiring example for flow control application
100% of output frequency of above figure is equivalent to maximum output frequency.
K
p
can be chosen between 0.2 and 5.0 in function [A71].
4 bit of digital
input signal
Fig. 2-3 Relation between deviation and output frequency of SJ100/L100
Max. frequency <--- 100
75
50
Output
frequency
(%)
25
100 75 50 25 0
Deviation(%)
K
p
=2
K
p
=1
K
p
=0.75
Kp=0.5
Kp=0.25
0 2 5 0 . .
≤ ≤
K p