Hitachi X200-002SFE/NFU Instruction Manuals page 196

PID Loop Configuration
The inverter's PID loop algorithm is configurable for various applications.
PID Output Limit - The PID loop controller has a built-in output limit function. This
function monitors the difference between the PID setpoint and the loop output (inverter
output frequency), measured as a percentage of the full scale range of each. The limit is
specified by parameter A078.
• When the difference |(Setpoint – loop output)| is smaller than or equal to the A078
• When the difference |(Setpoint – loop output)| is larger than the A078 limit value,
The diagram below shows PID setpoint changes and the related output frequency
behavior when a limit value in A078 exists.
Error Inversion - In typical heating loops or ventilation loops, an increase in energy into
the process results in an
cooling loops, an increase in energy into the process results in a
case, the Loop Error = –(SP – PV). Use A077 to configure the error term.
Other PID-related topics:
•
•
•
•
More user manuals on
limit value, the loop controller operates in its normal linear range.
the loop controller changes the output frequency as needed so that the difference
does not exceed the limit.
%
Output limit
A078
PID Setpoint
Output freq.
A078
Output limit
increasing
A077 =00
SP
Error
+
Σ
calculation
-
PV from process with
PV
positive correlation
"PID Control" on page 3–22
"PID ON/OFF and PID Clear" on page 4–26
"Output Deviation for PID Control" on page 4–41
"PID Second Stage Output" on page 4–45
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Limit imposed
on output
PV. In this case, the Loop Error = (SP – PV). For
SP
Freq.
-
PID
Limit imposed
on output
t
decreasing
PV. In this
A077 =01
Error Freq.
PID
Σ
calculation
+
PV from process with
PV
negative correlation
4−57