Danfoss VLT AutomationDrive FC 301 Programming Manual page 253

VLT AutomationDrive FC 301/302
Programming Guide
5.8 Parameter Group 7-** Controllers
5.8.1 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 large motor.
External Set-point
Illustration 72: Concept of 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 drive 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 drive 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.
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.
Enabling PID droop
To enable speed PID droop:
• Run the drive in 1 of the following modes:
-
Flux closed loop (parameter 1-01 Motor Control Principle, [3] Flux w/ motor feedb).
-
Flux sensorless (parameter 1-01 Motor Control Principle, [2] Flux sensorless).
•
Run the drive in speed mode (parameter 1-00 Configuration Mode, option [0] Speed open loop or [1] Speed closed loop).
• Ensure that parameter 1-62 Slip Compensation contains the default value (0%).
• Ensure that all drives in the torque sharing system use the same speed reference and start and stop signal.
Danfoss A/S © 2022.12
Drive 1
Set-point
Ramp
Calculation
Drive 2
Set-point
Ramp
Calculation
Drive 3
Set-point
Ramp
Calculation
Speed
-
PID
Droop
Speed
-
PID
Droop
Speed
-
PID
Droop
AU275636650261en-000101 / 130R0334 | 253
Parameter Descriptions
Torque
M1
PID
Torque
M2
PID
Torque
M3
PID