Transformers and power quality - Part II

This article investigates the generation of high harmonics in the magnetizing current of small three-phase transformers using the magnetic field analysis, the Finite Element Method (FEM). Through the analysis of the magnetic field in low power three-phase transformers, the magnetizing current waveform in the three phases of the transformer was obtained. The Fourier transform was then applied to obtain the harmonic analysis of the phase currents and determine their harmonic spectrum. Using the magnetic field analysis approach, the study aims to show that the generation of high harmonics in three-phase transformers – either low power ones or the power transformers in the electricity network – significantly influences the quality of electricity and its deterioration

Transformers and power quality - Part II

This article investigates the generation of high harmonics in the magnetizing current of small three-phase transformers using the magnetic field analysis, the Finite Element Method (FEM). Through the analysis of the magnetic field in low power three-phase transformers, the magnetizing current waveform in the three phases of the transformer was obtained. The Fourier transform was then applied to obtain the harmonic analysis of the phase currents and determine their harmonic spectrum. Using the magnetic field analysis approach, the study aims to show that the generation of high harmonics in three-phase transformers – either low power ones or the power transformers in the electricity network – significantly influences the quality of electricity and its deterioration

Transformers and power quality - Part I

This article examines issues related to power quality and generation of higher harmonics in single-phase transformers of low power supply, supplying electricity to household, office and industrial equipment. A simulation of the generation of higher harmonics of these transformers was performed based on the results of the analysis of the magnetic field using the Finite Element Method (FEM). Harmonic composition of the current in the primary side was determined using a Fourier transform applied to the curve of the current obtained through the analysis of the magnetic field using FEM. The results were fully confirmed by the experimental study of the harmonic composition of the current in the primary side of the investigated one-phase transformer using a digital oscilloscope. The used approach is unique, and it enables manufacturers to explore the harmonic composition during the design stage, and take appropriate measures to reduce their magnitude

DISTRACTION EXTERNAL FIXATIONS OF PELVIC FRACTURES CAUSED BY A LATERAL COMPRESSION.

The authors represent a distraction external pelvic fixation technique, which they use in pelvic fractures caused by a lateral compression. They consider the indications and mounting techniques. The authors recommend the early movement activities (on the 3rd - 5th day) after the external fixator placement. This method had been used in 8 patients and 3 cases are analyzed in details. The priority of this technique over open reduction and internal fixation (ORIF) mainly are: (1) the implementation of good reduction of the fracture preventing the risk of ORIF; (2) the possibility for early movement activities for the patient

Seventh course in ent surgery at “Trakia” hospital: 10 years cochlear implantation center in Stara Zagora

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Eosinophilic granuloma of the skull bone: a case report Langenharns cell granulomatosis

Eosinophilic granuloma is a rare benign tumor which is a variety of histiocytosis-X with unknown etiology. Eosinophilic granuloma occurs as single or multiple lesions of bone destruction. The eosinophilic granuloma of the skull can be asymptomatic or presented with pain and swelling. We present a clinical case of 20-years-old female patient who has entered the Neurosurgery clinic of “St. Marina” University Hospital with clinical manifestation of growing and painful tumor formation in the left frontal area for several weeks. MRI scan discovered evidence of a tumor formation on the left frontal side of the skull, suspicious for an eosinophilic granuloma. Under general anesthesia, an operative treatment was performed. Total extirpation of the tumor mass was achieved and cranioplasty with titanium mesh of the bone defect was performed. Posteratively, the patient had a good cosmetic effect, she was mobilized on the first day after the intervention and discharged from the hospital on the 5th day. Surgery-related complications were not observed. In the postoperative period the patient was followed-up by a hematologist. It is important and recommended for clinicians to include eosinophilic granuloma in the differential diganosis of bone lesions in patients because of the possible expansion of the disease if untreated. A follow-up of a year is necessary for possible recurrence

Osteoplasty in Surgical Treatment of Chronic Exogenous Osteomyelitis

Introduction: The aim of our research is to show the role of osteoplasty and surgical treatment of chronic exogenous osteomyelitis and to present exact rules of performing its different types - primary osteoplasty (PO - right after the renovation of the area of the infection), primary delayed osteoplasty (PDO - till the 30th day after the renovation of the area of infection ) and secondary osteplasty (SO - after more than 30 days after the renovation of the area of infection ).Many authors recommend performing of PO and many others claim that the best way of performing the procedure is PDO, based on results of their own researches. The dispute PO or PDO (SO) has continued for many years, but recently with the improved possibilities of planning ahead, the various ways of antibacterial treatment, the osteoplasty suggestions of the second group authors is starting to sound more convincing.Materials and Methods: We present 255 patients suffering from chronic exogenous osteomyelitis with defect of the bones, which means cases, in which two types of activities need to be performed:1. Removing bone infection from the osteomyelitic area by sanitizing it; 2. Creating good conditions for the bone consolidation via fixation (internal, external) and osteoplasty.Results: In 205 cases, we have sanitized the osteomyelitic area by using fixation and osteoplasty at the same time (PO). In 50 cases, because of the inability to perform PO, we proceeded with PDO or SO later.A good result would be a lack of bone infection and presence of bone consolidation for the first year. We observed that in 90% of PO and 60% of PO and PDO. Because of our database, we consider that PO should be prioritized if sanitizing the osteomyelitic area is performed perfectly.Conclusions: Based on our data we consider that PO is a priority if the renovation of the area of infection is performed perfectly