PM fractional machines adopting bonded magnets: effect of different magnetizations on the energetic performance

The adoption of Permanent Magnets in small brushless machines for automotive applications is becoming frequent. Some research on bonded magnets is being carried on to substitute the ferrites. In the paper the parallel and radial magnetizations are considered: the different process complexity levels are analyzed and the effects on the iron losses and the energetic performances are evaluated by means of a simulation analysis and its experimental validatio

Evaluation of the magnetization direction effects on ferrite PM brushless fractional machines

Permanent magnets are frequently adopted in small brushless machines for automotive applications. Normally anisotropic ferrites, but some research on bonded magnets is being carried on. Several types of magnetization can be proposed, involving different levels of complexity in the magnetization process. In the paper a comparison between parallel and radial magnetization is described, taking into account on one side the major complexity of the radial process and on the other the small power derating of the paralle

Digital Current-Control Schemes

The paper is about comparing the performance of digital signal processor-based current controllers for three-phase active power filters. The wide use of nonlinear loads, such as front-end rectifiers connected to the power distribution systems for dc supply or inverter-based applications, causes significant power quality degradation in power distribution networks in terms of current/voltage harmonics, power factor, and resonance problems. Passive LC filters (together with capacitor banks for reactive power compensation) are simple, low-cost, and high-efficiency solution

Direct torque control for dual three-phase induction motor drives

A direct torque control (DTC) strategy for dual three-phase induction motor drives is discussed in this paper. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. The DTC strategy is based on a predictive algorithm and is implemented in a synchronous reference frame aligned with the machine stator flux vector. The advantages of the discussed control strategy are constant inverter switching frequency, good transient and steady-state performance, and low distortion of machine currents with respect to direct self-control (DSC) and other DTC schemes with variable switching frequency. Experimental results are presented for a 10-kW DTC dual three-phase induction motor drive prototype

Enhanced Stray-Load Loss Measurements Through a Zig-Zag Variable Load Test Approach

This article proposes an enhanced procedure for executing the standard variable load test that allows obtaining high correlation factors for indirectly measured stray-load loss during efficiency tests of induction motors. This helps to achieve the minimum values required by the international standards to consider the variable load test well executed, avoiding unwelcome test repetitions and leading to significant amount of time saved. With the machine at steady-state temperature, the enhanced procedure consistsofalternativelyapplyingloadlevelshigherandlowerthan the rated load, so that the stator winding temperature zigzags aroundtheratedvalue.Hence,multiplereadingscanbeperformed for each load point, having the machine in isothermal conditions. This allows averaging many measurements of the same load point to mitigate the impact of instrumentation and reading errors. The article includes load tests conducted on different induction motor sizesandpolecounts,applyingboththestandardvariableloadtest procedure and the proposed approach. The experimental results show that theproposed technique allows achieving higher correlation factors on the stray-load losses than the standard procedure

Off-Line Efficiency Mapping of Induction Motors Operated in Wide Torque-Speed Ranges

In the context of a progressive component virtualization for energetic assessments in variable speed and load operations, this paper presents a methodology for computing the efficiency maps of three-phase induction motors. The proposed approach is based on the conventional machine equivalent circuit to quickly obtain a set of efficiency maps at different machine temperatures and supply voltage levels. The well-known no-load and locked-rotor tests are used to determine the motor parameters at different frequencies and voltages, taking into account the machine nonlinearities and the iron losses. The approach has been validated on an 11 kW, 4 poles, 50 Hz induction motor tested in different operating conditions

Temperatures evaluation in an integrated motor drive for traction applications

The integrated propulsion motor is a drive designed for an individual self-driven container rail-platform wagon developed in the ldquointegrated standard transport unitrdquo research and development project, supported by the European commission. This paper presents the study of the motor and the converter temperatures at rated and overload working conditions. The problem is afforded by combining the simulation (finite-element method and lumped-parameter models) and the experimental approaches. For this purpose, a dedicated experimental setup has been designed and realized

Accurate Induction Machines Efficiency Mapping Computed by Standard Test Parameters

The extensive electrification process that is taking hold in several applications makes increasingly necessary the virtualization of electric components for energetic and performance assessments during the system design stage. For this purpose, this paper proposes a straightforward methodology for computing the efficiency maps of induction machines operated in wide torque-speed ranges. The modeling approach is based on the induction machine equivalent circuit defined in the rotor dq coordinates. The procedure allows computing a set of efficiency maps at different machine temperatures and supply voltage levels, both for motor and generator operation modes. The equivalent circuit parameters at different frequencies and voltages are determined by means of the well-known no-load and locked-rotor tests, thus including in the modelling the machine nonlinearities, skin effect and the iron losses. The proposed methodology has been validated on a 10 kW, 4-pole induction machine. The comparison between computed and experimental efficiency maps for different operating conditions, confirm the validity of the proposed methodology

Design and Analysis of High-Speed Induction Machines for Submerged Cryogenic Pumps

This paper discusses the electromagnetic design and loss analysis of a 15 kW, 13500 rpm induction machine for a single-stage submerged cryogenic pump. The study starts from an existing machine driving a three-stage cryogenic pump, rated 7.5 kW at 7300 rpm. The new motor design is approached by increasing the rotating speed of the reference machine at fixed outer diameter, aiming at an optimum between efficiency and power factor. Experimental investigations are carried out on the reference machine to analyze its thermal behavior. The results allow to obtain initial values for the electrical loadability of cryogenic induction machines. The electromagnetic design of the high-speed motor is successfully carried out with the help of detailed numerical simulations, particularly devoted to a precise analysis of the losses active in the machine. Special care is given to the iron losses, estimated with two different approaches

Малое и среднее предпринимательство: закономерности развития

Представлен анализ уровня развития, достигнутого малыми и средними предприятиями, а также индивидуальными предпринимателями в Российской Федерации. Рассмотрены основные показатели функционирования предпринимательских структур по видам экономической деятельности. Приведены зависимости, показывающие распределение средней численности работников. Показана возможность разработки производственных функций для совокупности малых, средних предприятий и индивидуальных предпринимателей. Сделаны выводы об основных закономерностях развития предпринимательских структур