Efficient Networks S120 manual Motor model change, Vector control 4.3 Speed controller

Vector control 4.3 Speed controller

●Compared with speed control without an encoder, the dynamic response of drives with an encoder is significantly better because the speed is measured directly and integrated in the model created for the current components.

●Higher speed accuracy

Motor model change

A model change takes place between the current model and the observer model within the speed range p1752*(100%-p1756) and p1752. In the current model range (i.e at lower speeds), torque accuracy depends on whether thermal tracking of the rotor resistance is carried out correctly. In the observer model range and at speeds of less than approx. 20% of the rated speed, torque accuracy depends primarily on whether thermal tracking of the stator resistance is carried out correctly. If the resistance of the supply cable is greater than 20% to 30% of the total resistance, this should be entered in p0352 before motor data identification is carried out (p1900/p1910).

To deactivate thermal adaptation, set p0620 = 0. This may be necessary if adaptation cannot function accurately enough due to the following general conditions: for example, if a KTY sensor is not used for recording the temperature and the ambient temperatures fluctuate significantly or the overtemperatures of the motor (p0626 ... p0628) deviate significantly from the default settings due to the design of the motor.

4.3Speed controller

Both closed-loop control procedures with and without an encoder (VC, SLVC) have the same speed controller structure, which contains the following components:

●PI controller

●Speed controller pre-control

●Droop

The total of the output variables result in the torque setpoint, which is reduced to the permissible magnitude by means of the torque setpoint limitation.

Speed controller

The speed controller receives its setpoint (r0062) from the setpoint channel and its actual value (r0063) either directly from the speed sensor (control with sensor (VC)) or indirectly via the motor model (control without sensor (SLVC)). The system deviation is increased by the PI controller and, in conjunction with the pre-control, results in the torque setpoint.

When the load torque increases, the speed setpoint is reduced proportionately when droop is active, which means that the single drive within a group (two or more mechanically connected motors) is relieved when the torque becomes too great.

Drive Functions	119
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4