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Abstract: Reliable functioning of a power electronic switching device is limited not only by the instantaneous device junction temperature but also by its variation. A technique for reducing the device temperature variation is described. A simplified mathematical model of the thermal process in the device is evaluated in real time to estimate the instantaneous device temperature. A temperature control loop adjusts the device switching losses to compensate changes in conduction loss, thus keeping the total losses, and hence the temperature, substantially constant. This principle is applied to a pulsed power supply and to a PWM converter operating at a very-low-frequency (0.1Hz) output power modulation. The amplitude of device temperature variations is reduced by at least 50%. [Copyright &y& Elsevier]

The operation of a brushless permanent-magnet machine requires rotor-position information, which is used to control the frequency and phase angle of the machine's winding currents. Sensorless techniques for estimating rotor position from measurements of voltage and current have been the subject of intensive research. This paper reviews the state of the art in these sensorless techniques, which are broadly classified into three types: motional electromotive force, inductance, and flux linkage. [ABSTRACT FROM AUTHOR]

Microscopic voids in the die attachment solder layers of power semiconductor devices degrade their overall thermal transfer performance. This paper presents analytical results of the effect of spherical and spheroidal void geometries on the thermal conductivity of bulk media. Analytical results are compared with axially symmetric and three-dimensional thermal simulations of single and multiple cavity defects in planar structures. The effective thermal conductivity of the die to case attachment solder layer of two commercial metal oxide semiconductor field effect transistor (MOSFET) devices is estimated using these results, with cavity dimensions and distributions obtained by electron microscopy. [ABSTRACT FROM AUTHOR]

Features a study which devised a strategy for device switching and voltage vector selection in direct torque control (DTC). Background of DTC; Leg-switching strategy in DTC; Inverter switching process; Experimental results.

Describes a novel algorithm for the estimation of rotor position in a switched reluctance motor based on recursive least-squares estimator. Capability of the algorithm to extract information about rotor position at very low speeds from voltage and current waveforms; Position estimation procedure.

Introduces a flywheel energy storage device capable of enhancing the fuel economy of a hybrid-type road vehicle. Speed range; Power requirements; Machine type; Rotor construction; Effect of pole number and core back depth upon iron loss.

Describes a modern solution to real-time rotor position estimation of brushless permanent magnet (PM) motor drives. Details on the two types of control used to drive brushless PM motors; What is the estimation scheme based on; Methodology used in the description process; Features of PM motors; Information on the conventional way of measuring rotor position in brushless PM motors.

The most advanced vacuum cleaners are now using brushless drives, with operating speeds in excess of 100 000 r/min. The drives are very sophisticated, but must also be low in cost. Sensorless control is desirable, but most sensorless methods involve extensive computation, which is prohibitively expensive at such high speeds. This paper looks at a 100 000-r/min, 1600-W switched reluctance machine (SRM) and drive system using the current gradient sensorless (CGS) scheme and analyzes parameters that affect the stability of the system. Commercial products require very robust control schemes: effects such as motor magnetic saturation, speed variations, changes in advance angle, and changes in dc-link voltage are examined to determine the boundaries within which the CGS scheme is stable. Both simulation and measurements are used, demonstrating measures which ensure stable operation over the entire operating range. [ABSTRACT FROM PUBLISHER]