Danfoss VLT AutomationDrive FC 301 Programming Manual page 175

Parameter Descriptions
3.8.2 Speed PID Droop
This feature implements precise torque sharing between
multiple motors on a common mechanical shaft.
Speed PID droop is useful for marine and mining
applications, where redundancy and higher dynamics are
required. Speed PID droop allows to reduce inertia by
utilizing multiple small motors instead of 1 big motor.
Set-point
Calculation
Set-point
External Set-point
Calculation
Set-point
Calculation
Illustration 3.47 Speed PID Droop
The value in parameter 7-01 Speed PID Droop ensures that
the load is shared equally between the motors. If the
torque on the motor is 100% of nominal motor torque, the
frequency converter reduces its output to this motor by
100% of the value in parameter 7-01 Speed PID Droop. If the
torque is 50% of nominal motor torque, the frequency
converter reduces its output to this motor by 50% of the
value in parameter 7-01 Speed PID Droop. This ensures that
the motors share the load evenly.
A side effect of using speed PID droop is that the actual
shaft speed does not match the reference exactly. Speed
PID droop is not efficient in low-speed applications
because the adjustment range may be insufficient.
M0013101
Programming Guide
VLT 1
Ramp
VLT 2
Ramp
VLT 3
Ramp
Danfoss A/S © 10/2019 All rights reserved.
Illustration 3.47 shows the concept of the feature:
Speed
-
PID
Droop
Speed
-
PID
Droop
Speed
-
PID
Droop
Use speed trim if the application requires the following
features:
•
Accurate speed (the actual shaft speed matches
the reference speed).
•
Precise speed adjustment down to 0 RPM.
Torque
M1
PID
Torque
M2
PID
Torque
M3
PID
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