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Propagating brush discharges can release large amounts of energy. From the point of view of safety, this feature makes them among the most destructive electrical discharges. This paper provides a survey of recent work in the modeling of propagating brush discharges. Experimental data from various authors are compared with a discharge model in which areas of a charged surface are modeled as capacitive cells, and bridges between cells are modeled as spark gaps driven by the tangential electric field between cells. A theory that explains the physics of this particular type of discharge is presented. Charge transfer and post-discharge charge distributions are compared between the theory and the experimental data of several authors. [ABSTRACT FROM AUTHOR]

This paper describes the dynamic overmodulation strategies for fast torque control of the high-saliency-ratio ac motor. For the high-saliency-ratio ac motor, the dynamic control of both d- and q-axes currents is required for fast torque control with optimal efficiency. However, in transient operation, the d- and q-axes current regulators are easily saturated even at low speed because the stator inductance is designed large enough to generate the desired reluctance torque. With the conventional overmodulation strategies, the current regulation performance degrades severely compared to a nonsalient motor. In this paper, the drawbacks of the conventional overmodulation strategies are investigated and a dynamic overmodulation strategy is proposed to improve the current response to fast transients. For the effective implementation of the strategy, a practical algorithm is also presented. The performance of the proposed strategy is con- firmed by computer simulation and experiment with a 3.75-kW axially laminated synchronous reluctance motor and an interior Permanent-magnet synchronous motor for 42-V integrated starter-generator applications. [ABSTRACT FROM AUTHOR]

The concept of lightly ferromagnetic rotor bars to improve the starting performance of squirrel-cage induction motors is presented in this paper. Although the induction machines are popular for their ruggedness and simplicity, their starting torque is low and the starting current is 5-8 times higher than the rated current. A simple solution to this problem is the introduction of new rotor-bar material with lightly ferromagnetic properties, which in turn improves the starting power factor due to enhanced skin effect. Relevant electromagnetic theory supporting this is e presented in this paper. A computer simulation also produced expected re sults. A 1-hp induction machine has been tested to verify the proposed methodology. [ABSTRACT FROM AUTHOR]

This paper presents a new three-phase 12/8-pole doubly salient permanent-magnet (DSPM) machine for application to wind power generation. The key is to design and analyze the proposed DSPM generator, namely, the design of a new machine structure to achieve high power density and high robustness and the device of system operation to attain high efficiency. By using finite element analysis, the static characteristics of the proposed generator are given. Hence, the evaluation of system performances is conducted by computer simulation. Experimentation is also given to verify the validity of the proposed DSPM generator. [ABSTRACT FROM AUTHOR]

Strong circumstantial evidence suggests that lightning has initiated methane explosions in abandoned and sealed areas of underground coal mines. The Mine Safety and Health Administration (MSHA) investigated several of these occurrences within recent years. The investigated explosions occurred at significant depths, ranging from 700 to 1200 ft. Data from the National Lightning Detection Network indicated a strong correlation between the times and locations of the explosions with those of specific lightning strikes. This paper proposes that corona discharge from a steel borehole casing is the most likely mechanism responsible for these ignitions. A recently investigated mine explosion and fire at a depth greater than 1000 ft was selected for this study. Computer simulations were performed, using data collected at the mine site. CDEGS software from Safe Engineering Services & Technologies, Ltd. and MaxwellSV from Ansoft Corporation were used for the simulations. [ABSTRACT FROM AUTHOR]

Multioop control strategies have commonly been used to control power inverters of both the voltage-source and current-source topologies for power conversion applications including uninterruptible power supplies and utility interfaces for distributed power generation. However, these control strategies tend to be developed and comparatively evaluated for a particular application, with strategies for other applications presented as independent new developments. This paper presents a generalized analysis of different multiloop control approaches using alternative feedback control variables for several popularly adopted system configurations, highlighting similarities and identifying a generalized optimal control-variable selection criterion that is applicable across most multiloop-controlled inverter systems. The generality of the presented optimal variable selection criterion has been verified through the close similarities between the time-domain waveforms of the different inverter systems simulated in MATLAB Simulink and implemented experimentally in the lab- oratory. [ABSTRACT FROM AUTHOR]

Many mathematical models have been developed to describe the lateral dynamics of a moving web, including Shelton's model. Experimental results in this study showed that the existing model does not fully describe the characteristic of the lateral dynamics for some typical operating conditions. An experimental model was derived by means of system identification using a well-known least-square method to improve the prediction capability of the lateral dynamics. A commercial guidance system usually has the proportional and integral control structure. Sometimes it may not eliminate the effect of periodic lateral disturbances efficiently which are transferred from upstream spans because the controller relying solely on feedback generates control action only when an output measurement signal differs from a reference value. However, if the disturbance is deterministic, a feed forward control structure may offer simple and effective disturbance rejection performance. In this paper, the lateral position of a web at the upstream span and the identified model of lateral dynamics for the span were used to estimate the effect of disturbance on the lateral dynamics of a moving web at the exit span of the guidance system. A feed forward controller was designed to reject the deterministic disturbance of lateral dynamics of a moving web. The disturbance rejection performance of the proposed controller was verified by computer simulation and experiments. These results showed that the proposed feed forward scheme with an improved mathematical model greatly improved control performance in overcoming the dynamic disturbance. [ABSTRACT FROM AUTHOR]

The condition of rolls has significant influence on the process conditions such as longitudinal tension and lateral error in web transport systems such as in metal and film processes. In particular, a roll-shape defect such as an eccentricity is a major cause for the periodic tension disturbance in the web. In this paper, the authors aim to reject these disturbances caused by unknown shapes of rolls. In order to reject the tension disturbance due to the roll shape, an adaptive eccentricity estimator and eccentricity compensation methods are proposed. The validity of the compensation method including the adaptive eccentricity estimator was tested through computer simulation and experimental study. [ABSTRACT FROM AUTHOR]

A magnetically levitated motor (MLM) with two directions of movement is presented in this paper. The thrust and the levitation force of the proposed motor can be achieved simultaneously by using only a single power source. Analytical equations for the operation principle of the proposed MLM are derived. Computer simulations of the MLM characteristics by using the finite-element-analysis method are also presented. The same trend can be found between analytical equations and computer-simulation results. Then, some experimental results are provided to confirm the theoretical analysis. All of the results can provide very useful information of mechanical-structure design and control scheme development for the MLM. [ABSTRACT FROM AUTHOR]

Neutral-point-clamped converters are increasingly applied in industrial drive systems as they allow the use of lower voltage devices in higher voltage applications, provide reduced output voltage total harmonic distortion (THD), and can develop low common mode voltage. Several distinct modulation strategies have been proposed in the past for eliminating the common mode voltage, providing low THD output voltage or reducing the neutral point current ripple. However, each of these strategies improves the performance of the converter on one metric while trading off performance in other metrics. Nearest three vector, radial state, and zero-common-mode types of space-vector modulation techniques are compared using metrics that clearly elucidate the performance tradeoffs. Analytical models, computer simulation results, and experimental verification are presented. [ABSTRACT FROM AUTHOR]

An electronic throttle is a low-power dc servo drive which positions the throttle plate. Its application in modem automotive engines leads to improvements in vehicle drivability, fuel economy, and emissions. Transmission friction and the return spring limp-home nonlinearity significantly affect the electronic throttle performance. The influence of these effects is analyzed by means of computer simulations, experiments, and analytical calculations. A dynamic friction model is developed in order to adequately capture the experimentally observed characteristics of the presliding-displacement and breakaway effects. The linear part of electronic throttle process model is also analyzed and experimentally identified. A nonlinear control strategy is proposed, consisting of a proportional-integral-derivative (PH)) controller and a feedback compensator for friction and limp-home effects. The PID controller parameters are analytically optimized according to the damping optimum criterion. The proposed control strategy is verified by computer simulations and experiments. [ABSTRACT FROM AUTHOR]