Acionamento de máquinas à relutância variável.

Abstract

The use of variable reluctance machines (\"RM) as viable system have been waited for the development of suitable motor drive systems. These systems must be able to accomplish operacional requirements as fast current commutation among the phases and also the knowledge of the axis position. In spite of V R M favorable inner characteristics as construction simplicity, concentration of the electric windings of the stator, better torque volume relationship, low inertia and operation capability at high speeds, the YRM presents high torque ripple due to its double saliency structure and switching current effects among phases, that moves i t away of high performance applications, as robotics. The difficulty of generating torque with low ripple is outlined by the use of strategies that control the form and the instants of current application for the phases of the machine based on the characteristic curves of inductance and derived of inductance versus position of it. The accurate knowledge of these curves allows implementing high performance systems. In this work, it will be analyzed some procedures that allow to obtain these curves in a faster way. keeping the precision of the estimation method based on the flux x current x position curves The current loop control is one of the most important loops in a drive system based on variable reluctance machines. Among the more commonly used controllers, stand out the hysteresis control and PWM, usually implemented with PI or PID regulator. The first controller is indicated for operations in high-speed while the second one is more efficient in low and medium speeds. An alternative to the previous controllers is the predictive controller, which is proposed in this work. It will be shown that the use of this type of controller for regulation of the variable reluctance machine phase current is technically viable and simple and robust to parametric variations as well. The implementation of the control action is accomplished by the inverter switches command that is usually for a voltage source inverter. The variable reluctance machines can operate w i t h unidirectional currents simplifying the project of the inverter and allowing the use of inverter w i t h just a switch for each phase, but imposing severe operation restrictions to the machine. The use of the inverter with integrated structures, as the three phase bridge inverter are shown as alternatives to drive variable reluctance machines. Following this direction, i t w i l l be presented alterations in the form as these structures have been used allowing them to reach equivalent performance to the half bridge inverter. To conclude, the effects of the dead time compensation will be analyzed in three phase bridge inverters. In spite of the simplicity and efficiency of the compensation strategies

based on the modification of the inverter switches command pulses, i t will be shown that the strategies should be monitored to avoid that the command compensated times extrapolate the up or down limits of the sample time. This situation can cause distortion in the synthesized voltage by the inverter.