Danfoss FC 102 Design Manual page 42

Introduction to VLT® HVAC D...
Function
2 2 Set acceptable limits for
the motor speed.
Switch from open loop to
closed loop.
4) Configure the feedback to the PID controller.
Select the appropriate
reference/feedback unit.
5) Configure the set-point reference for the PID controller.
Set acceptable limits for
the set-point reference.
Select current or voltage by switches S201 / S202
6) Scale the analog inputs used for set-point reference and
feedback.
Scale Analog Input 53 for
the pressure range of the
potentiometer (0 - 10 Bar,
0 - 10 V).
Scale Analog Input 54 for
pressure sensor (0 - 10
Bar, 4 - 20 mA)
7) Tune the PID controller parameters.
Adjust the frequency
converter's Closed Loop
Controller, if needed.
8) Save to finish.
Save the parameter
setting to the LCP for safe
keeping
Table 2.15 Programming Order
2.8.12 Tuning the Frequency Converter
Closed Loop Controller
Once the frequency converter's closed loop controller has
been set up, the performance of the controller should be
tested. In many cases, its performance may be acceptable
using the default values of 20-93 PID Proportional Gain and
20-94 PID Integral Time. However, in some cases it may be
helpful to optimise these parameter values to provide
faster system response while still controlling speed
overshoot.
2.8.13 Manual PID Adjustment
1. Start the motor.
2. Set 20-93 PID Proportional Gain to 0.3 and
increase it until the feedback signal begins to
oscillate. If necessary, start and stop the
frequency converter or make step changes in the
40
Design Guide
Paramete Setting
r
4-12 10 Hz, Motor min speed
4-14 50 Hz, Motor max speed
4-19 50 Hz, Drive max output
frequency
1-00 [3] Closed Loop
20-12 [71] Bar
20-13 0 Bar
20-14 10 Bar
6-10 0 V
6-11 10 V (default)
6-14 0 Bar
6-15 10 Bar
6-22 4 mA
6-23 20 mA (default)
6-24 0 Bar
6-25 10 Bar
20-93 See Optimisation of the
20-94 PID Controller, below.
0-50 [1] All to LCP
Danfoss A/S © Rev. 06/2014 All rights reserved.
set-point reference to attempt to cause
oscillation. Next reduce the PID proportional gain
until the feedback signal stabilizes. Then reduce
the proportional gain by 40-60%.
3. Set 20-94 PID Integral Time to 20 s and reduce it
until the feedback signal begins to oscillate. If
necessary, start and stop the frequency converter
or make step changes in the set-point reference
to attempt to cause oscillation. Next, increase the
PID integral time until the feedback signal
stabilizes. Then increase of the integral time by
15-50%.
4. 20-95 PID Differentiation Time should only be used
for very fast-acting systems. The typical value is
25% of 20-94 PID Integral Time. The differential
function should only be used when the setting of
the proportional gain and the integral time has
been fully optimised. Make sure that oscillations
of the feedback signal are sufficiently dampened
by the low-pass filter for the feedback signal
(parameters 6-16, 6-26, 5-54 or 5-59 as required).
MG11BC02