No abstract

Applications such as electrolysis, electrowinning, DC arc furnaces and plasma torches require high-current (several kA) power supplies at low-voltage levels (few hundreds of volts). In this study, conventional rectifier topologies (diode-and thyristor-based multi-pulse rectifiers with on-load tap changing transformer and chopper-rectifier) used for high-current, variable-voltage applications are reviewed along with recent advancements in the field. The main applications themselves are also discussed. Issues with conventional topologies are highlighted. Power quality techniques like passive and active filters are discussed for power factor and current harmonics compensation. Advanced medium-to high-frequency transformer-based topologies (with current and voltage source rectifiers) are discussed along with simulation results.

No abstract

No abstract

A complete model-based control for traveling-wavetype ultrasonic motors is presented in this paper. The control scheme consists of inner control loops with respect to the oscillation systems, offering all meaningful degrees of freedom for adjusting the traveling bending wave, and outer control loops for torque and speed. After a brief review on modeling the actuator and presentation of a parameter identification method, the control scheme is developed and verified by measurements on a prototype drive system. Several measures for the compensation of nonlinearities and temperature effects are developed and achieved improvements are discussed with respect to the special properties of this novel actuator. Finally the developed drive is applied to an "active control stick."