Continued
n087 : Integral Time Factory setting: 10.0 seconds
(PID I Time)
Range: 0.0 to 100.0 seconds
This parameter determines how fast the integral gain increase is added to the
control loop.
n088 : Derivative Time Factory setting: 0.0 seconds
(PID D Time)
Range: 0.00 to 1.00 seconds
Derivative time can be adjusted to dampen initial oscillations and reduce overshoot,
which serves to improve stability.
These parameters are all interactive, and will need to be adjusted until the control loop is
properly tuned, i.e. stable with minimal stead-state error. A general procedure for tuning
these parameters is as follows:
1. Adjust Proportional Gain until continuous oscillations in the Controlled
Variable are at a minimum.
2. The addition of Integral Time will cause the steady-state error to approach
zero. The time should be adjusted so that this minimal error is attained as
fast as possible, without making the system oscillate.
3. If necessary, adjust derivative time to reduce overshoot during startup.
The drive’s accel and decel rate times can also be used for this purpose.
H. n089 : Integral Value Limit Factory setting: 100 %
(PID I Limit)
Range: 0 to 109 %
Parameter n089 is factory set for optimum results for most applications, and generally
doesn’t need to be changed.
I. n036 thru n040 : Multi-function Input Terminals
(Terminal S2-S6 Sel)
PID I Reset ( 20 ): Integral Value Reset
A Multi-function Input Terminal can be used to reset the value of n087 to data " 0 ".
Note that this value is also reset to " 0 " if the drive is given a STOP command.
PID Disable ( 21 ): PID Disable
A Multi-function Input Terminal can be used to disable PID control. When this terminal
is closed, PID control is disabled, and the Setpoint Reference is used as the frequency
reference.
5-48
5.22 PID CONTROL
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