Danfoss FC 300 Design Manual

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Danfoss FC 300 Design Manual Manual pdf 34 page image

3.4.2 Tuning PID speed controlThe following tuning guidelines are relevant when using one of the Flux motor control principles in applications where the load is mainly inertial (with alow amount of friction).The value of par. 7-02Speed PID Proportional Gain is dependent on the combined inertia of the motor and load, and the selected bandwidth can becalculated using the following formula:Par. 7 − 02 =Total inertia k gm 2x par. 1 − 25Par. 1 − 20x 9550x Bandwidth rad /sNote: Par. 1-20Motor Power [kW] is the motor power in [kW] (e.g., enter ‘4’ kW instead of ‘4000’ W in the formula). A practical value for the bandwidthis 20 rad/s. Check the result of the par. 7-02Speed PID Proportional Gain calculation against the following formula (not required if you are using a highresolution feedback such as a sin-cos feedback):Par. 7 − 02MAXIMUM = 0.01x 4x Encoder Resolution x Par. 7 − 062x πx Max torque ripple %A good start value for par. 7-06Speed PID Lowpass Filter Time is 5 ms (lower encoder resolution calls for a higher filter value). Typically, a max torqueripple of 3% is acceptable. For incremental encoders, the encoder resolution is found in either par. 5-70Term 32/33 Pulses per Revolution (24V HTL onstandard drive) or par. 17-11Resolution (PPR) (5 V TTL on MCB102 Option).Generally, the practical maximum limit of par. 7-02Speed PID Proportional Gain is determined by the encoder resolution and the feedback filter time,but other factors in the application might limit the par. 7-02Speed PID Proportional Gain to a lower value.To minimize the overshoot, par. 7-03Speed PID Integral Time could be set to approx. 2.5 s (varies with the application).Par. 7-04Speed PID Differentiation Time should be set to 0 until everything else is tuned. If necessary, finish the tuning by experimenting with smallincrements of this setting.3.4.3 Process PID ControlProcess PID control can be used to control application parameters that can be measured by a sensor (i.e., pressure, temperature, flow) and be affectedby the connected motor through a pump, fan or otherwise.The table shows the control configurations where the process control is possible. When a flux vector motor control principle is used, take care also totune the speed control PID parameters. Refer to the section about the Control Structure to see where the Speed Control is active.par. 1-00ConfigurationModepar. 1-01Motor Control PrincipleU/f VVCplus Flux sensorless Flux w/ enc. feedb[3] Process N.A. Process Process & Speed Process & SpeedNote: The Process Control PID will work under the default parameter setting, but tuning the parameters is highly recommended to optimize the applicationcontrol performance. The two flux motor control principles are specially dependant on proper speed control PID tuning (prior to tuning the process controlPID) to yield their full potential.3 Introduction to AutomationDrive FC 300 FC 300 Design Guide3-18 MG.33.BC.22 - VLT® is a registered Danfoss trademark3