4-2 Function Mode „ PID Output Limit Function •This function limits PID output within a variable range relative to the target value. •To use this function, set PID output limit function A078. The output frequency will be limited within a range of "target value ± (A078)", with the maximum frequency defined as 100%. •With A078 set to 0.0, this function is disabled. PID output (%) PID output range PID target value PID variable range (A078) PID variable range (A078) 4 Time (s) Functions „ PID Reverse Output •When a PID operation result is a negative value under normal PID control, the frequency reference to the Inverter is limited at 0 Hz.
However, if PID selection A071 is set to "02" (reverse output enabled), reverse output can be provided for the Inverter when the PID operation result is a negative value. •When A071 = 02, the above-mentioned PID variable range limit function and the PID output stop function are disabled. „ PID Gain Adjustment •If a stable response cannot be obtained in PID function operation, adjust each gain as follows according to the situation. •Feedback value variation is slow when the target value is changed. → Raise P gain A072. •The feedback value changes fast but isn't stable. → Lower P gain A072. •The target and feedback values wouldn't match smoothly. → Lower I gain A073.
•The feedback value fluctuates unstably. → Raise I gain A073. •Response is slow even with P gain raised. → Raise D gain A074. •With P gain raised, the feedback value vibrates and isn't stable. → Lower D gain A074. „ Excessive Deviation/Output •You can set PID deviation excessive level C044 during PID control. With this function allocated, the multi-function output terminal is turned on when the PID deviation ε reaches the set level in C044. •C044 can be set from 0 to 100. The setting corresponds to the range of 0 to the maximum target value. •Allocate 04 (OD) to any of multi-function output terminals C021 to C025 or relay output terminal C026.
„ Feedback Comparison Signal •If a PID feedback value is out of the specified range, it can be output to a multi-function output terminal. •Allocate 31 (FBV) to any of multi-function output terminals C021 to C025 or relay output terminal C026. 4-34