The research is devoted to the investigation of NdFeB permanent magnet (PM) based synchronous generators with non-overlapping concentrated windings. The rotor of such a generator has 10 pole pairs (PMs), which is dictated by the nominal voltage frequency (f=50 Hz) and the rotational speed (n=300 RPM). Comparison is made for four generators with three-phase winding coils and stator tooth numbers 18, 21, 24 and 27.
The paper considers the possibility to use permanent magnets in the rotor slots of axial inductor machine with the aim to create a hybrid excitation of such a machine - from the magnets and from the excitation winding which is placed between the stator cores. The hybrid excitation allows the weight and size parameters of the machine to be improved. Under consideration is a 32 kW under-carriage generator 2ГB.13.Y1.
Direct-Drive Contactless Wind Generator with Concentrated Winding
A clear trend has emerged in the field of wind power industry concerning the creation of low-, medium-, and even high-power direct-drive wind turbines without the use of gearboxes. Such generators are usually multipolar and mostly excited from permanent magnets. In the low-speed performance, multipolarity means a higher specific torque and reliability as well as lower operating costs, which in the case of high-speed generators is hindered by gearboxes. Multipolarity with a high specific torque can be achieved mainly through the use of permanent magnets of high-energy materials (such as NdFeB) and through design solutions for the armature winding. The authors compare two most common types of wind generator's armature windings: the distributed one, which contains a coil embracing several teeth, and the concentrated armature winding - with one coil for one stator tooth. The comparison (along with the experience in developing the wind turbines) shows that the con-centrated winding version has a number of advantages, the main of them being the multipolarity. This means that the generator with a concentrated winding can be more acceptable for the direct-drive wind turbines, is easier to make and simpler to operate. Another very important advantage of concentrated windings shown in this work is that they allow achievement of a higher specific electromagnetic torque, which means smaller size and weight of such a generator in the low-speed version.
Comparative analysis is performed for different motors from the standpoint of damage inflicted by them during their lifecycle. Three types of motors have been considered: the synchronous reluctance motor, the permanent magnet assisted synchronous reluctance motor and the induction motor. The assessment of lifecycle has been made in terms of its four stages: manufacturing, distribution, use and end of life. The results show that the production costs of synchronous reluctance motor are lower compared to that of permanent magnet assisted motors, but due to their low efficiency they exert the greatest environmental impact. The main conclusion is that the assessment made at the early designing stage for the related environmental impact enables its reduction.
The paper discusses problems concerning the influence of permanent magnet material characteristics on the low-speed permanent magnet generator losses and output characteristics. The variability of the magnet material and its effect on the output parameters of the machine has been quantified. The characteristics of six different grades of neodymium permanent magnets have been measured and compared to the supplier specification data. The simulations of the generator have been carried out using transient finite element analysis. The results show that magnet materials from different suppliers have different characteristics, which have a significant influence on the generator output parameters, such as efficiency and power factor.
The paper discusses the current developments in the recycling of electrical machines. The main attention is devoted to three types of motors: synchronous reluctance motor, permanent magnet assisted synchronous reluctance motor, and induction motor. Base materials of such electrical machines are also described in the paper. Rare-earth permanent magnets used in electrical machines are review separately. Moreover, the paper considers the features of the disassembly and recycling options.
The paper discusses issues related to the optimisation of magnetic couplings used in bioreactors (manufactured by JSC “Biotehniskais Centrs”). The purpose of optimisation was to preserve the maximum breakaway torque of the magnetic coupling while reducing the mass of rare earth elements used in its structure. The paper presents the rationale for the selected optimisation option taking into account the economic aspect. To solve the optimisation problem, the factors affecting the maximum torque of the magnetic coupling, such as the shape and height of the internal and external magnets, the angle of the external and internal magnets, as well as the height of the internal and external yoke, were determined. The design of the existing magnetic coupling was optimised and its prototype was made based on the results of optimisation. The results obtained by means of optimisation were compared with the results obtained experimentally by testing the manufactured prototype.
Mastocytosis is a heterogeneous group of disorders characterized by abnormal growth and accumulation of mast cells (MCs) in the skin and/or other organ systems. Mastocytosis is a rare disease. The annual incidence is 5–10 cases per 1 million people. However, the majority of cases stay undiagnosed due to the lack of specific tests and a wide variety of clinical features of the disease. In mastocytosis, somatic mutations of KIT gene lead to autocrine dysregulation and constitutive c-KIT activation in the absence of its ligand SCF. Clinical symptoms of the disease are determined by MC mediator release and/or infiltration of tissues by MCs. According to the World Health Organisation classification updated in 2016 mastocytosis is divided to cutaneous mastocytosis (CM), indolent systemic mastocytosis (ISM), smoldering systemic mastocytosis (SSM), SM with an associated hematologic (non-MC-lineage) neoplasm (SMAHN), aggressive SM (ASM), MC leukemia (MCL) and MC sarcoma (MCS). The CM and ISM prognosis is excellent with (almost) normal life expectancy, unlike aggressive forms (ASM and MCL) with poor prognosis. In this paper the key aspects of clinical features and diagnostic criteria of mastocytosis are discussed. We present a case report of a patient with mastocytosis in the skin following psoralen plus ultraviolet A (PUVA) therapy with good response.