In this paper, a novel sensorless commutation method for BLDC motors is presented to eliminate simultaneously phase shifter and low-pass filter. An analytical model of the motor is presented, and the ripples resulted from the current commutation are investigated in details. By detecting the zero crossing points of the unfiltered voltages of the motor terminals with regard to the ground and to the DC link, the commutation signals can be generated using a set of proposed logical equations. The extracted commutation points are phase delay-free, because the low-pass filters have been eliminated. Therefore, the proposed method can be used in a wide range of speeds. Moreover, the method is cost-effective because it does not need any phase shifters. Simulation and real-time implementation results show the effectiveness of the proposed method.

First, the impedance source idea is used to alleviate the problems of Voltage Source Inverters (VSI), and Current Source Inverters (CSI), which leads to the introduction of the Z-Source Inverter (ZSI). Afterwards, not only did the Z-source cells were used in the inverter topologies, but they were also added to other power electronic converters, such as dc-dc choppers, ac-dc rectifiers, and ac-ac converters. Moreover, these power electronic converters, which have Z-source cells, are widely used in different applications. In particular, the existing single-phase ac-ac Z-source converters are reviewed in this paper, and their different features are studied in detail. In the past decades, the single-phase Z-source ac-ac converters have attracted significant attention due to their unique features, such as single-stage power conversion, boost in-phase, and buck out-of-phase features. Therefore, several modified or improved structures along with different control methods have been introduced to solve their problems and limitations. Based on the four features, these structures can be categorized into four groups: without magnetic coupling, with magnetic coupling, able to change the frequency, and inherent commutation. In this review, a general diagram is depicted, which many of the existing topologies can be obtained from it. Additionally, new topologies can be obtained by having this general diagram. After studying these structures, a comparative study is made to obtain the advantages and disadvantages of each. In the end, some advice and recommendations are given to develop and obtain new structures.

This paper presents the method of reducing torque ripple of brushless DC (BLDC) motor. The commutation torque ripple is reduced by control of the DC link voltage during the commutation time. The magnitude of voltage and commutation time is estimated by a neural network and optimized with an optimization method named particle swarm optimization (PSO) algorithm analysis. The goal of optimization is to minimize the error between the command torque and real torque and doesn't need knowledge of the conduction interval of the three phases. It adaptively adjusts the DC link voltage in commutation duration so that commutation torque ripple is effectively reduced. In this paper, the performance of the proposed brushless DC (BLDC) control is compared with that of conventional BLDC drives without input voltage control.

This paper presents an original study on the generated torque ripples of phase commutation in the Four-Switch, Three-Phase Inverter (FSTPI) Brushless DC (BLDC) motor drive which is suitable for low cost applications. Analytic values of torque ripple and commutation duration are obtained for different operation conditions. Moreover, limitation on the speed range operation caused from splitting of the DC-link voltage is shown exactly.Then a novel current control technique is developed to minimize the commutation torque ripple for a wide speed range. The technique proposed here is based on a strategy that the current slopes of the rising and the decaying phases during the commutation intervals can be equalized by proper duty-ratios at commutations. Finally, the validity of the proposed analysis and developed torque ripple reduction technique are verified via simulation.

Background and purpose: Nowadays over 153 million women use IUD worldwide as contraception. Long-term durability, high efficacy, and cost effectiveness are advantages of this method.This study compares the side effects and continuation rate of TCu380A and Cusafe (300, +300) IUDs during a 6-month period in Taamine Ejtemaee clinics, Hamadan, Iran.Materials and methods: This was a description study. By using a continued method, 250 candidates applied for IUD were randomly placed in two groups of IUD. The side effects and continuation rate were recorded in the following 1,2,3,6 months. Statistical analysis was performed using Students t-test, fisher and chi-squared test where appropriate. The method for data collection was using some information record whose reliability and validity had been approved by the authorities in the field and after data collection they were analyzed statistically.Results: Vaginal bleeding was the most common consequence during the first month of implantation in both groups, however in months 1, 2, and 6 vaginal bleeding was significantly less prevalent in Cu safe group. At all intervals Cu safe users were complained for pain and infection significantly less than that in the TCu380A group. The continuation rate was significantly higher in the 3rd month for Cu safe users. No other major differences in spontaneous expulsion and contraceptive failure were found between the study groups.Conclusion: According to our findings, the side effects included bleeding; pain, infection and spontaneous expulsion were less incident in Cu safe users than TCu380A. Therefore, the use of Cu safe IUD is recommended.

Background: IUD is a useful and effective tool for family planning. Different kinds of this equipment are available at the market, but currently the most commonly used one in our country is CU T380A. Previous studies have shown that CU safe 300 is more effective and associated with less complications than CU t380A, thus it is more acceptable by users. The aim of this study was to determine and compare failure rate of CU T380A and CU safe 300 IUDS, four years after insertionMaterials and methods: The present research is a cohort study carried out on 246 women who referred to health clinics of Khorramabad four years ago. These women divided into two equal groups. One group used CU T380A and the other group used CU safe 300. The rate of unwanted delayed complications such as spontaneous bleeding, pregnancy and spontaneous repelling of the IUDs were assessed by a questionnaire. Data were analyzed by Chi square and paired T test.Results: Failure rate of CU T380A was more than CU safe 300. Statistical tests showed significant differences between these two groups.Conclusion: This study shows that new IUD (CU safe 300 ) which are smaller in size have less Failure rate and more acceptable by women, so their use is suggested in health clinics.

The commutation process causes current ripple to be generated in the drive system of brushless DC (BLDC) motor. This, in turn, leads to torque ripple that causes mechanical vibration and acoustic noise which are undesirable phenomenon in some applications. A new method is presented in this paper which reduces torque ripple and commutation period in the entire range of motor speed. This method is designed and implemented using two-segment pulse-width modulation (PWM) and DC-link voltage doubling during commutation. Based on the presented theory and given the influence of DC-link voltage on ripple magnitude, some experiments were carried out in which simultaneous contribution of the above mentioned factors in reducing current ripple and commutation time in the entire speed range of rotor are shown. The experimental results showed that the current ripple magnitude in high speed range is almost 20 times less than conventional method based on H-PWM_L-ON technique.