Specifications

Function Paramete
r
Setting
Set acceptable limits for
the motor speed.
4-12
4-14
4-19
10 Hz, Motor min speed
50 Hz, Motor max speed
50 Hz, Drive max output
frequency
Switch from open loop to
closed loop.
1-00
[3] Closed Loop
4) Configure the feedback to the PID controller.
Select the appropriate
reference/feedback unit.
20-12
[71] Bar
5) Configure the set-point reference for the PID controller.
Set acceptable limits for
the set-point reference.
20-13
20-14
0 Bar
10 Bar
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).
6-10
6-11
6-14
6-15
0 V
10 V (default)
0 Bar
10 Bar
Scale Analog Input 54 for
pressure sensor (0 - 10
Bar, 4 - 20 mA)
6-22
6-23
6-24
6-25
4 mA
20 mA (default)
0 Bar
10 Bar
7) Tune the PID controller parameters.
Adjust the frequency
converter’s Closed Loop
Controller, if needed.
20-93
20-94
See Optimisation of the
PID Controller, below.
8) Save to finish.
Save the parameter
setting to the LCP for safe
keeping
0-50
[1] All to LCP
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
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).
Introduction to VLT® HVAC D... Design Guide
40 Danfoss A/S © Rev. 06/2014 All rights reserved. MG11BC02
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