Pid Loop Operation - Hitachi X200-002SFE/NFU Instruction Manuals

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PID Loop Operation

In standard operation, the inverter uses a reference source selected by parameter A001
for the output frequency, which may be a fixed value (F001), a variable set by the front
panel potentiometer, or value from an analog input (voltage or current). To enable PID
operation, set A071=01. This causes the inverter to
A calculated target frequency can have a lot of advantages. It lets the inverter adjust
the motor speed to optimize some other process of interest, potentially saving energy as
well. Refer to the figure below. The motor acts upon the external process. To control that
external process, the inverter must monitor the process variable. This requires wiring a
sensor to either the analog input terminal [O] (voltage) or terminal [OI] (current).
When enabled, the PID loop calculates the ideal output frequency to minimize the loop
error. This means we no longer command the inverter to run at a particular frequency,
but we specify the ideal value for the process variable. That ideal value is called the
setpoint
application it may be gallons/minute, or it could be air velocity or temperature for an
HVAC unit. Parameter A075 is a scale factor that relates the external process variable
units to motor frequency. The figure below is a more detailed diagram of the function.
NOTE: You cannot use [O] and [OI] simultaneously. For example, if you select [OI] to
setpoint, it is not possible to use [O] as a Process Variable, and vice versa.
More user manuals on
Setpoint
Error
PID
+
Calculation
SP
PV
, and is specified in the units of the external process variable. For a pump
Setpoint
(Target)
Standard setting
F001
Scale factor
Reciprocal
Multi-speed
1
settings
A075
to
A020 A035
Potentiometer on
keypad
V/I input
select
[AT]
Process Variable (Feedback)
A GND
L
O
Voltage
OI
Current
A076 PID V/I input select
ManualsBase.com
calculate
Freq.
Inverter Motor
Process Variable (PV)
Frequency
source select
Scale factor
A001
SP
+
Analog input scaling
A012
Scale factor
A011
A015 A013 A014
the target freq, or setpoint.
External
Process
Sensor
A072 F001
P gain
A072
Frequency
setting
I gain
+
A073
D gain
A074
Monitor
A075 D004