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The aim of this work was to eliminate the backflow power present in an isolated three-port DC–DC converter. Backflow power (which is an inherent property of phase-shifted DC–DC converters) is the major contributor of circulating current the converter, which in turn is known to be the leading cause of system loss. The dual phase shift (DPS) control scheme (which alters the transformer voltage waveform at the different winding terminals) was used to reduce the backflow power. Mathematical relations for the backflow power present in the three-port converter were derived. And from this equation, an operating point in which the backflow power is zero was also obtained. This condition for zero backflow power was confirmed by simulations on PSIM. Added to this were simulation results that show other operating conditions in which zero backflow power could be obtained in the converter. In addition, equations for the power processed at the different ports of the converter were also presented, and 3D plots were made to illustrate the variation of the power and backflow power with respect to the phase shift ratios of the DPS control scheme. It was observed that the backflow power can be totally removed from the three-port converter when using this control scheme. [ABSTRACT FROM AUTHOR]

This paper deals with a design of the exciter which is a self-magnetizing apparatus of a written-pole motor (WPM). For a given rotor of 0.2 hp WPM, the pole shape and winding specifications of the exciter which is driven by a general voltage are optimally designed. Then, with consideration of hysteresis characteristics of a magnetic layer, the magnetization waveform is investigated with Preisach model. To validate the results calculated in design and analysis, the experimental test is carried out and comprehensive test results are suggested. Index Terms--Exciter, hysteresis, magnetization, Preisach, written pole motor.

This paper proposes a newly structured double excited two-degree-of-freedom (DOF) motor with tilt/pan motion to use in a security camera. For applications in active vision, a tilt/pan mechanism should be accurate, fast, small, inexpensive, and have low power requirements. We have designed a new type of motor meeting these requirements, which incorporates both tilt and pan into a single, two-degree-of-freedom device. The focus of the research is to design the improved 2-DOF motor which can eliminate the drawbacks as manufacturing, complicated control, and difficulty in lamination in conventional model. Additionally, to effectively improve the torque characteristic, the main pole pitch and the auxiliary pole shape are determined by the pan motion and the tilt motion, respectively. The validity of proposed structure will be shown in the computer simulation of the newly structured double excited 2-DOF motor for security cameras. Index Terms--Multi-degree-of-freedom (DOF), security camera, spherical motor, tilt/pan, 3-D finite-element method.

This paper describes a new position sensorless starting method, specialized for low-cost applications, of a brushless dc (BLDC) motor with a surface permanent-magnet (SPM) rotor to prevent demagnetization of permanent magnet and vibrations due to pulsating currents during the starting period. That the magnitude of peak current causes irreversible demagnetization of permanent magnet, has been measured through experimental tests. The proposed method limits the motor currents during the starting period to lower than the demagnetization currents by doing commutation depending on the level of the measured phase currents. Experimental results show that the proposed method implemented in an inverter for a BLDC motor-driven reciprocating compressor considerably reduces not only the pulsating currents but also the vibration of the compressor during starting. Index Terms--Brushless dc motor, reciprocating compressor, sensorless control, starting method.

This paper presents a novel method to reduce commutation torque ripple in a position sensorless brushless dc (BLDC) motor drive. To compensate the commutation torque ripple considerably, conventional methods should know commutation interval, so that they need current sensors. However, the proposed method measures commutation interval from the terminal voltage of a BLDC motor, calculates a pulsewidth modulation (PWM) duty ratio using the measured commutation interval to suppress the commutation torque ripple, and applies to the calculated PWM duty ratio only during the next commutation. Experimental results verify that the proposed method implemented in an air conditioner compressor controller considerably reduces not only the pulsating currents but also vibrations of a position-sensorless BLDC motor. Index Terms--Brushless dc (BLDC) motor, commutation torque ripple, sensorless drive.