The researches on direct AC-AC converters have been an important field. The DC-modulated method, which was used in DC-DC converters before, is used in AC-AC converters to realize a direct AC-AC converting now. The traditional control method regulates the output by adjusting the duty ratio. Its’ core is the PWM technology. In this paper, the variable structure control (VSC) strategy was utilized...

Background Some comparative studies have reported improved outcomes for early compared with delayed reconstruction high-grade acromioclavicular (AC) joint dislocations. However, most are based on older techniques and did not specifically involve of both the coracoclavicular (CC) AC ligaments. The purpose this study was to compare functional vs. surgical intervention dislocations managed combine...

The reconstruction of PET brain data in a PET/MR hybrid scanner is challenging in the absence of transmission sources, where MR images are used for MR-based attenuation correction (MR-AC). The main challenge of MR-AC is to separate bone and air, as neither have a signal in traditional MR images, and to assign the correct linear attenuation coefficient to bone. The ultra-short echo time (UTE) MR...

This paper presents the choice between the utilizing a lower cost die cast or fabricated aluminium rotor versus the more expensive copper bar rotor. In industrialized countries Induction motors account for approximately 50% of the overall electricity use. In every field whether it is agricultural sector or the economical sector. The power consumption by a.c motors is quite enough. On an average...

in this study, a manganite sample with a nominal formula of la0.9sr0.1mno3 was prepared by the microwave assisted sol-gel method and annealing at various temperatures. the structural and magnetic properties of the samples were investigated by xrd, fesem and ac susceptometer, respectively. xrd analysis showed that the samples are a nearly single phase. fesem micrographs showed that by increasing...

The Nyquist sampling theorem states that band limited signals may be represented without error by sampled data. Among the effects which place additional restrictions on the signal, beyond those which are given by the Nyquist theorem, are aperture effects. Aperture effects such as aperture jitter, and aperture time, contribute to a signal degradation which is frequency dependent. In applications...

This paper presents some implementation details of a threephase to three-phase matrix converter prototype. The bidirectional semiconductor switches were built using discrete IGBTs and fast diodes. Design aspects such as protection against overvoltage and short-circuit, commutation process Artigo submetido em 23/04/2010 (Id.: 1132) Revisado em 18/09/2010, 15/07/2011, 30/08/2011 Aceito sob recome...

Multilevel converters are powerful converters in the medium-voltage high-power range. Inside this family of converters, the three-level neutral point clamped converter has its own importance. The main control methods associated with this converter are the carrier-based PWM with added DC components and the space vector PWM. Two of the most important features of the NPC converter are the neutral ...

Matrix converter is a single-stage converter which directly connects a three-phase voltage source to a three-phase load without dc-link components. Therefore, any harmonic distortion and imbalance in input voltage directly reflect to the output of the converter. Recently, many researchers have made an effort to cope with this problem. In this paper, under distorted input voltage conditions, beh...