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Showing 2 results for Mirzaeian
Volume 12, Issue 4 (3-2013)
Abstract
The Direct Torque Control (DTC) of Interior Permanent Magnet Synchronous Motor (IPMSM) offers simple structure and fast torque response. The conventional Switching Table-based DTC (ST-DTC) presents some disadvantages like high torque and flux ripple and also variable switching frequency. This paper investigates the improved ST-DTC strategies to reduce both torque and flux ripple in DTC of IPMSM with emphasis on structure simplicity and fast dynamics. New switching table with only two active vectors for each sector is introduced and the torque control hysteresis band is replaced by duty cycle calculation unit. For flux ripple reduction, conventional hysteresis-based controller is replaced by simple dithering technique. The duty cycle calculation unit is implemented to operate on each selected vector with the aim of torque ripple RMS minimization. The increase of switching frequency in ST-DTC because of delay in torque and flux estimation process, actually, is not possible; even when hysteresis bands are sufficiently diminished. This paper incorporates the combination of duty cycle modulated DTC and dithering technique to enlarge switching frequency. It therefore provides smoother waveform concurrently for the motor torque and the flux. In the proposed method waveform comparison structure for duty cycle calculation is used; hence, the merits of classical ST-DTC, such as fast dynamic and simple structure, are mostly preserved
Volume 12, Issue 5 (November & December, (Articles in English & French) 2021)
Abstract
Annually, a good number of Iranian students who have completed their undergraduate studies in non-English-related majors apply and enroll in Master’s level Teaching English as a Foreign Language (TEFL) programs. Although evaluating MA TEFL program in Iran from university instructors’ and students’ perspectives has so far been the subject of several studies, the experiences and views of these TEFL major-changers have not been duly explored. To address the existing gap, in this qualitative research, the experiences of major-changers studying TEFL at MA level in three state universities in Tehran have been investigated. Besides, six TEFL university instructors were asked to share their perspectives concerning major-changers attending MA TEFL programs. In the main, the findings revealed that motives like interest in pursuing an English teaching career rather than a job related to their former major; gaining the required competency through attending crash courses held by university exam preparatory institutes; facing challenges in acquiring the specialized discourse of the community; and witnessing realities which ran counter to their prior supposition, as discussed by the major-changers and the instructors, formed part of the lived experiences and views of these major-changers.
