AN improved method of optimization for electrical machines

Methods of optimizing the design of electrical machines are discussed. The augmented Lagrangian multiplier method is described, and an algorithm for this method is introduced. The method is compared with the more familiar exterior penalty function method using, as an example, the cost optimization of permanent magnetic variable-speed drive motors. The improved method is shown to be superior, both in its ability to reach an optimum consistently and in the number of required iterations     

Procedures for analysis of strain transfer in the acetabular region in vitro

The failure of acetabular cups via loosening, migration or fracture is partially related to the stress distribution existing in the acetabular region. The complexity of the investigation of these stresses demands the application of a variety of model testing techniques involving combined embedded strain gauging, finite element analysis, transmission and reflective photoelasticity and crack propagation studies. The application of these procedures are described and the difficulties of obtaining representative loadings and restraints are commented upon.     

Analysis of a PWM AC to DC voltage source converter under thepredicted current control with a fixed switching frequency

A detailed analysis of a pulse-width modulated AC to DC voltage source converter under the proposed predicted current control with a fixed switching frequency (PCFF) is presented. A steady-state analysis, a dynamic response analysis, a high-frequency component analysis, and their solutions are also provided. The results show that the converter under the PCFF control has a fast dynamic response, ease of control, and a good switching pattern. The theoretical derivation is experimentally verified     

Conceptualizations of novice and experienced counselors.

We examined the conceptualizations of 23 (11 experienced and 12 novice) counselors, with respect to general counseling process and specific client concerns by means of a two-part conceptual mapping task (CMT). Analyses of the CMT data revealed an interaction effect of counselor experience and generality of conceptual task on the extensiveness of counselor conceptualizations. Experienced counselors displayed slightly more extensive conceptualizations on the general CMT and less extensive conceptualizations on the specific CMT. This interaction effect was interpreted as evidence that experienced counselors possess extensive abstract, general knowledge of counseling that they use to conceptualize specific instances of counseling efficiently and parsimoniously. On the other hand, novice counselors, who lack such abstracted knowledge, engage in more extensive, unique conceptual work for each separate client. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the design of high-performance surface-mounted PM motors

This paper considers the major design factors which constrain the maximum acceleration capability of surface-mounted neodymium-iron-boron permanent magnet motors as used in servo drives. Expressions are derived for typical achievable values of the air-gap flux density and the linear current density around the stator periphery. For applications with small values of the duty factor, the stator linear current density is limited by the need to avoid demagnetization. For larger values of duty factor, the constraint is the ability of the cooling system to remove the heat losses within the magnet and insulation temperature limits. The paper derives general approximate expressions for maximum torque and acceleration limits, and shows graphs from which the range of acceleration capability of a permanent magnet motor in a given application can be assessed. The constraints involved in matching the motor design to an inverter with given maximum voltage capability are also discussed     

Steady-State Analysis of a Permanent Magnet Synchronous Motor Drive with Current Source Inverter

A steady-state analysis is presented of a permanent magnet (PM) synchronous motor drive with a current source inverter (CSI). The torque-speed profile required of the drive is a constant torque region from zero to base speed and a constant power region above base speed. The analysis assumes position feedback control. Optimum control strategies are obtained for the two regions of the torque-speed profile. Using these optimum strategies, performance curves of the drive are predicted and experimentally verified. The time harmonics in the motor are a function of the presence and configuration of the dampers in the motor. An expression is obtained for the equivalent inductance seen by the harmonics for different damper configurations. A Fourier series approach is used to predict the line-to-line voltage waveforms. Even though the presence of the dampers is not essential to the operation of the drive, their presence reduces the voltage spikes present in the line-to-line voltage.     

Synchronous Motor Drive with Current-Source Inverter

Steady-state properties of a variable-speed drive using a synchronous motor fed by a controlled current-source inverter are derived from an equivalent circuit model, including saturation, and are confirmed by experiment. The system is shown to be stable under all operating conditions. Control strategy for open-loop operation is discussed.     

Distributed steady state nonlinear modeling of turboalternators

This paper presents an alternate approach for modeling of steady state performance of large turboalternators including the effects of magnetic saturation. To avoid the superposition limitations of the conventional d-q approach, a sectoral model of a pole of the machine is developed and solved iteratively. The computational effort is orders of magnitude less than for a finite element solution. Results from the proposed model are compared with those from a conventional d-q model and with measurements made for a wide range of load conditions on a 588-MVA turbogenerator     

Cognitive mediation in person-centered and rational-emotive therapy.

Relations among counselor and client cognitive and behavioral variables were examined in relation to counselor and client ratings of counseling effectiveness. Unlike previous cognitive-mediational process research on counseling, the conceptual and coding systems used were tailored specifically to two different counseling approaches. Data were obtained from videotapes of 20 counseling sessions and from 40 stimulated recall interviews with both counselors and clients following the counseling sessions. Ten of the sessions followed a rational-emotive format; 10 followed a person-centered format. Both therapeutic conditions consisted of two dyads, each studied experimentally during 5 sessions selected from brief counseling interventions. Results indicated that variables composed from both cognitive and behavioral data predicted participant ratings of counseling effectiveness more than did behavioral variables alone. As in previous research, such relations seemed to depend on a strong negative correlation between counselor transparency (accurate client perceptions of counselor intentions) and participant ratings of counseling effectiveness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)