Search

Economic justification of electric drives is the primary reason for many applications. However, the cumbersome trial-and-error calculations necessary to present this aspect often leads to omission of the topic in electric drives courses. This paper presents a MATLAB-based program that generates plots of input power and shaft torque for variable-frequency operation of three-phase induction motors. Based on these graphs, an example is presented illustrating how a cost amortization study for an adjustable speed drive application can be presented with minimal effort and lecture time. Index Terms--Electric drives, motor-drive cost study, variable-frequency induction motors.

A novel dc-link converter utilizing resonant commutation is presented. Since resonant commutation is accomplished, converter switches are thyristors (SCR's) with lower costs than forced commutated devices. Focus is on the variable-frequency operation of the converter, with potential application in variable-frequency custom power delivery or adjustable-speed motor drives. The converter operates with greater stored energy in the dc link, thus offering current holdup capabilities during a contingency which cannot be attained with a conventional resonant dc-link converter and achieves minimum switching losses without increased conduction losses. Harmonic elimination is achieved by employing sinusoidal pulsewidth modulation (SPWM) control of the converter. Simulation results and experimental validation of the resonant commutation of a low-voltage and low-power laboratory model are discussed. Work in progress and the scope of further work are discussed. Index Terms - Modulation index control, resonant commutation, resonant link converter, switching losses.

Unlike its rotary counterpart, the linear switched reluctance machine (LSRM) lends itself to double-sided excitation and multiple translator (or 'rotor') configurations that can yield high-force density designs suitable for controlled linear motion in hostile environments. This paper presents the particular design of a 6:4, double-sided, double-translator LSRM that develops 5.1 Ib/[in.sup.2] of air gap force shear. The work develops a permeance tube based method to allow simple algebraic magnetic circuit analysis and associated prediction of flux linkages regardless of the level of magnetic saturation of the ferromagnetic structure. Theoretical static thrust predictions are made based on the calculation of change in stored magnetic coenergy per unit distance of translator movement. Laboratory testing of a proof-of-principle LSRM, built up to verify the theoretical predictions, shows that the calculated and measured average thrust values agree within reasonable error over the range of excitation.