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Open access

H. May, R. Palka, P. Paplicki, S. Szkolny and W.-R. Canders

Modified concept of permanent magnet excited synchronous machines with improved high-speed features

Permanent magnet (PM) excited synchronous machines used in modern drives for electro-mobiles suffer in high speed regions from the limited battery-voltage. The field weakening requires designing machines with reduced power conversion properties or increasing the size of the power converter. A new concept of such a machine features PM excitation, single-tooth winding and an additional circumferential excitation coil fixed on the stator in the axial center of the machine. By the appropriate feeding of this coil, the amplitude of the voltage effective excitation field can be varied from zero to values above those of the conventional PM-machines. The capability of reducing the excitation field to zero is an important safety aspect in case of failing of the feeding convertor.

Open access

R. Caramia, R. Piotuch and R. Pałka

Abstract

The paper presents a methodology for the optimization of a Brushless Direct Current motor (BLDC). In particular it is focused on multiobjective optimization using a genetic algorithm (GA) developed in Matlab/Optimization Toolbox coupled with Maxwell from ANSYS. Optimization process was divided into two steps. The aim of the first one was to maximize the RMS torque value and to minimize the mass. The second part of the optimization process was to minimize the cogging torque by selecting proper magnet angle. The paper presents the methodology and capabilities of scripting methods rather than specific optimization results for the applied geometry

Open access

Duncan Palka, Mahinda Yogarajah, Hannah R. Cock and Marco Mula

Summary

Background. Epilepsy is among the most frequent neurological conditions and it is estimated that approximately 8% of the population experience a seizure at some time in their lives.

Aim. To examine the characteristics of patients referred to a First Seizure Clinic (FSC) at a University Hospital in South-West London.

Methods. All subjects referred to the FSC at St George’s University Hospitals between January and December 2015 were included in this audit.

Results. From a total of 257 patients, males 49.5%, age range 16–90, 30% referred by General Practices (GPs), 59.1% by the Accident & Emergency Department (A&E) and 10.9% by other hospital wards, 24.5% did not attend (DNA) the clinical appointment. Females who did not attend were significantly older than males (49.8 years old vs 39.7; p = 0.007). Among those who attended the clinical appointment, 17% were diagnosed first unprovoked seizure, 12.4% acute symptomatic seizure and 28.9% epilepsy. These patients were referred mainly by A&E while GPs referred seizure mimics especially non-epileptic attack disorder (NEAD) and syncope. Patients with NEAD were significantly younger than those with seizures (29.4 years old vs 44.2; p < 0.001) and had a previous psychiatric history (72.7% vs 16.8%; p < 0.001). The proportion of seizure mimics was similar in the older sample group (> 65 years). Regarding acute symptomatic seizures, 33.3% were alcohol-related, 20.8% acute brain insults and 12.5% drug-related (always overdose).

Conclusions. 1 in 4 patients referred to a FSC does not attend the clinical appointment, especially older females. More than 1 in 3 cases represent seizure mimics and are referred mainly by GPs.

Open access

G. Kwinta, S. Kara, B. Kalandyk, R. Zapała and P. Pałka

Abstract

The exposed selvedge layers in slabs cast by the continuous process should be free from surface defects, which in most cases appear in the form of cracks on the casting surface and run to its interior. In addition to the parameters of the casting process, the occurrence of such defects depends on the chemical composition of cast steel, on the segregation of surface active elements and formation of the precipitates of carbides, nitrides and other phases. Due to the frequent occurrence of defects in corners of the slabs, non-destructive testing was performed on the mechanically cleaned surfaces of slabs. The test material was low-carbon API(American Petroleum Institute API 5L standard) steel micro alloyed with Nb and Ti designed for the production of pipes to handle gas, oil and other liquid and gaseous fuels. Despite the use of different methods of inspection, i.e. ultrasonic, magnetic particle and penetrant, cracks were not traced in the examined material. Then, from the corners of the examined slabs, specimens were cut out for metallographic examinations. The main purpose of these examinations was to disclose the presence of possible cracks and micro cracks on the surfaces transversal and longitudinal to the direction of casting. At the same time, studies were conducted to establish the number and morphology of non-metallic inclusions in selvedge layers of the slab corners and axis. Additionally, hardness of the slabs was measured. The conducted studies revealed only some minor differences in the slab hardness along its axis (130 ÷ 135 HB) and in selvedge layers (120 ÷ 123 HB).

Open access

M. Marcinek, M. Hołub, S. Kalisiak and R. Pałka

Abstract

A technique for stabilization of resonant frequency is proposed in this paper. An additional power circuit, a compensator that allows keeping constant resonance frequency was introduced by the authors. In the presented solution the resonant circuit frequency stabilization is achieved by forcing a zero phase shift between the current and the voltage of the main switching module.