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Expert is concerned with the design, performance, and control of electrical energy conversion devices. He has research, development, and design experience in all types of variable-speed or constant-speed electromechanical drives, including variable-frequency/variable-voltage drives. He designed electric-hybrid, variable-speed drives for automobiles and variable-speed train drives for wind power plants employing insulated-gate bipolar transistors (IGBTs) for rectifier and inverter circuit components. The electric machines involved are mostly of the permanent-magnet type with neodymium-iron-boron (NdFeB) magnets with field weakening, resulting in high efficiencies.

A significant portion of Expert's career in the design of drives has involved the optimization of single- and three-phase induction motor drives concerning efficiency for given constraints (costs, performance characteristics). A comparison of several constrained optimization techniques involving nonlinear programming approaches leads to similar solutions. It can be expected that such optimal design techniques will be heavily used due to the recent passage of the Energy Policy Act of 1992.

Within the emerging field of power quality in power systems, Expert is an expert in the analysis of the generation, propagation, mitigation, and prevention of harmonics and fractional harmonics in distribution systems. He uses fundamental Newton-Raphson type load flow, harmonic load flow (HARMFLO), and the electromagnetic transients program (EMTP). He studied the impacts of voltage and current harmonics on power system components and end-user devices as well as the effects of geomagnetically induced currents in power systems.

In his design and development work, Expert routinely uses nonlinear magnetic field analysis such as finite element and finite difference methods in two and three dimensions. Applications of such methods include induction, synchronous, permanent-magnet, and homopolar machines; linear and rotary motion electromechanical actuators, magnets, and inductors. These numerical methods solve the linear and nonlinear Laplace, Poisson, and diffusion equations, that is, magnetostatic as well as electrodynamic field problems.

Expert's most recent work concerns the improvement of the seasonal energy efficiency ratio (SEER) of heat pumps and the design of variable-speed wind power plants, hybrid electric cars with the recovery of braking energy, and high-efficiency electric motors and drives exploiting permanent magnets. New materials such as compressed powdered iron cores are employed. Energy conservation is possible through motor efficiency improvement, distribution system power factor correction, mechanical system and motor matching with adjustable-speed drives, and process optimization.

Expert has designed pulse-width-modulated inverters and rectifiers and their simulation with SPICE. He has dealt with reverse-recovery currents of diodes and transistors and their suppression. Gating circuits with either transformer or optical coupling have been applied to single- and three-phase systems where the gating pulses are synchronized with an external periodic signal via a voltage-controlled oscillator. Control of inverters is made such that these devices can continuously change the power factor and waveshape of the output current.

Expert has consulted with numerous businesses concerning the application of electric machines, transformers, and actuators. He has resolved issues related to the rewinding of electric machines, harmonic currents in the neutrals of transformers, and the application of induction motors within boreholes. Electronically commutated DC, stepper, and switched reluctance motors, field-oriented control, and field weakening appear to be of recurring importance. He has advised on the design of magnetic couplings and electromagnetic actuators consisting of permanent-magnet and voice coil, as well as torque motors.

Most electric quantities encountered are nonsinusoidal, Expert maintains, so conventional analog metering is not possible. With the emergence of flexible PCs, analog to digital (A/D) and digital to analog (D/A) converters as well as programmable arbitrary waveform generators, the measurement of nonsinusoidal/sinusoidal quantities can be performed based on 12 to 16-bit sampled data acquisition networks. Expert has gained considerable laboratory experience through recent research and development work at the University of Colorado concerning online monitoring of transformer losses and derating.