Speed Trim - Danfoss VLT AutomationDrive EZ FC 321 Programming Manual

VLT® AutomationDrive EZ FC 321
Programming Guide
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.
• Ensure that all drives in the torque sharing system use the same parameter settings.
• Adjust the value in parameter 7-01 Speed PID Droop.
Do not use overvoltage control when using the PID droop function (select [0] Disabled in parameter 2-17 Over-voltage Control).
If the speed reference is lower than the value in parameter 7-01 Speed PID Droop, the drive makes the PID droop factor equal to
the speed reference.

4.8.2 Speed Trim

The speed trim function is an add-on to the speed PID droop. The speed trim provides torque sharing with precise speed down to
0 RPM. The function requires wiring of analog signals.
In speed trim, the master drive runs normal speed PID without droop. The follower drives use the speed PID droop, but instead of
reacting on their own load, they compare their own load to the load of other drives in the system. The follower drives then use that
data as input for the speed PID droop. A setup with a single source, where the master drive sends information about torque to all
followers, is limited by the number of available analog outputs on the master drive. It is possible to use a cascade principle which
overcomes this limitation, but makes the control slower and less accurate. The master drive operates in speed mode. The follower
drives operate in speed mode with the speed trim. The trim function uses torque data from all drives in the system.
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Parameter Descriptions
AU373327181955en-000101 / 130R1208 | 189