A self-commissioning method for permanent magnet dc-motor drives

The conventional model describing the electrical and mechanical properties of a permanent magnet dc-motor drive is extended in order to take into account the oscillations of the induced voltage that are caused by slotting effects, and - as the electrical machine investigated is fed from a PWM-inverter - in order to include the inverter´s voltage drop. Furthermore, a method is proposed to estimate the extended model´s parameters from one single experiment that is easy to be carried out. The method is based on recording the inverter´s dc-link voltage, the dc-motor´s armature current and the rotor´s angular position as a function of time while the dc-motor is fed from the inverter. As the inverter is controlled by a digital signal processor system, this can be done without using additional measuring devices, but just with the dsp-system´s measurement facility which is required anyway for the controlled operation of the drive. No additional mechanical components have to be coupled if the motor is equipped with an incremental encoder. Besides the method´s aptitude for self commissioning purposes, it is also perfectly suited for quality control as in addition to the relevant electrical parameters one can also estimate mechanical parameters (e.g. to describe the load torque). This makes it easy to control the assembly quality of the motor. Last but not least the model´s predictions are compared to experimental results and this comparison clearly shows the benefits of the method proposed.