Multiphase induction motor drives - a technology status review

The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operatio

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

Impact of PWM strategies on RMS current of the DC-link Voltage Capacitor of a dual-three phase drive

The major drawback of usual dual three-phase AC machines, when supplied by a Voltage Source Inverter (VSI), is the occurrence of extra harmonic currents which circulate in the stator windings causing additional losses and constraints on the power component. This paper compares dedicated Pulse Width Modulation (PWM) strategies used for controlling a dual three phase Permanent Magnet Synchronous machine supplied by a six-leg VSI. Since the application is intended for low-voltage (48V) mild-hybrid automotive traction, an additional major constraint arises: the compactness of the drive related to the size of the DC-bus capacitor. Thus, the PWM strategy must be chosen by taking into consideration its impact on both, the motor and the RMS value of DC-bus current

Vectorial formalism for analysis and design of polyphase synchronous machines

A vectorial formalism for analysis and design of polyphase synchronous machines without reluctance and saturation effects is described. We prove the equivalence of such a machine with a set of magnetically independent machines, which are electrically and mechanically coupled. Specific problems of polyphase machines can thus be favorably analyzed with this concept. Rules of conception and constraints on electric supply can be deduced. Moreover the vectorial approach, which generalizes the complex phasor method, can also be used to control n-leg Voltage Source Inverters. This methodology is applied to 3-phase and 6- phase synchronous machines

Detection and Diagnosis of Motor Stator Faults using Electric Signals from Variable Speed Drives

Motor current signature analysis has been investigated widely for diagnosing faults of induction motors. However, most of these studies are based on open loop drives. This paper examines the performance of diagnosing motor stator faults under both open and closed loop operation modes. It examines the effectiveness of conventional diagnosis features in both motor current and voltage signals using spectrum analysis. Evaluation results show that the stator fault causes an increase in the sideband amplitude of motor current signature only when the motor is under the open loop control. However, the increase in sidebands can be observed in both the current and voltage signals under the sensorless control mode, showing that it is more promising in diagnosing the stator faults under the sensorless control operation

Three-dimensional electromagnetic field model of an auger electromechanical converter with an external solid rotor

Purpose. Creating a three-dimensional mathematical model of the electromagnetic field of an auger electromechanical converter with the external solid rotor, taking into account the geometry peculiarities and the finite length factor. Methods. Calculation of the electromagnetic field distribution has been performed with the use of the computational solving the differential equations by the finite element method in a three-dimensional statement. Findings. It has been set that in the air gap the values of magnetic induction vary in the range of 0.7 – 0.8 T, in the flanks of the stator teeth they reach the value of 2 T. Induction in a hollow ferromagnetic rotor varies mainly in the range of 1.3 – 2.0 T, and in a thin layer with a thickness of 1.0 – 1.5 mm, facing the stator surface, it reaches the value of 2.3 T. Within one pole pitch, the z-component maximum of the eddy currents density is 18·106 A/m2 on the inner hollow rotor surface. It has been determined that, with the exception of the ‘edge’ rotor sections, where the transverse component of eddy currents prevails, as well as the sections of the magnetic flux “input” into the rotor, the eddy currents are mainly axial. A comparison of the results of measuring the electric field intensity on the rotor surface evidences a data difference of not more than 4%. The proposed model enables to optimize the design of the converter, in particular, to reduce the magnetic induction in the stator teeth. Originality. Numerical results have been obtained in the form of spatial patterns of distribution and graphical dependences that take into complete account the axial and tangential components of the electromagnetic field. Practical implications. The considered finite element model can be used when analysing the electromagnetic fields in electromechanical converters with a complex secondary part. This will give a possibility to consider the real three-dimensional field character, caused by the design peculiarities and the final axial dimensionsМета. Створення тривимірної математичної моделі електромагнітного поля шнекового електромеханічного перетворювача із зовнішнім масивним ротором, що враховує особливості геометрії і фактор кінцевої довжини. Методика. Розрахунок розподілу електромагнітного поля виконаний із використанням чисельного рішення диференціальних рівнянь методом кінцевих елементів в тривимірній постановці. Результати. Встановлено, що у повітряному зазорі значення магнітної індукції змінюються в діапазоні 0.7 – 0.8 Тл, в ніжках зубців статора досягають величини 2 Тл. Індукція в порожнистому феромагнітному роторі переважно змінюється в діапазоні 1.3 – 2.0 Тл, а в тонкому шарі товщиною 1.0 – 1.5 мм, зверненому до поверхні статора, досягає величини 2.3 Тл. В межах одного полюсного поділу максимум z-компоненти густини вихрових струмів становить 18·106 А/м2 на внутрішній поверхні порожнистого ротора. Визначено, що за винятком “крайових” ділянок ротора, де переважає поперечна складова вихрових струмів, а також ділянок “входу” магнітного потоку в ротор, вихрові струми в основному є аксіальними. Порівняння результатів вимірювання напруженості електричного поля на поверхні ротора показало відмінність даних не більше 4%. Запропонована модель дозволяє оптимізувати конструкцію перетворювача, зокрема, зменшити магнітну індукцію в зубцях статора. Наукова новизна. Отримано чисельні результати у вигляді просторових картин розподілу та графічних залежностей, які повністю враховують аксіальну та тангенціальну компоненти електромагнітного поля. Практична значимість. Розглянута кінцево-елементна модель може бути використана при аналізі електромагнітних полів в електромеханічних перетворювачах зі складною вторинної частиною. Це дозволить врахувати реальний тривимірний характер поля, викликаний особливостями конструкції і кінцевими осьовими розмірами.Цель. Создание трехмерной математической модели электромагнитного поля шнекового электромеханического преобразователя с внешним массивным ротором, учитывающей особенности геометрии и фактор конечной длины. Методика. Расчет распределения электромагнитного поля выполнен с использованием численного решения дифференциальных уравнений методом конечных элементов в трехмерной постановке. Результаты. Установлено, что в воздушном зазоре значения магнитной индукции изменяются в диапазоне 0.7 – 0.8 Тл, в ножках зубцов статора достигают величины 2 Тл. Индукция в полом феромагнитном роторе преимущественно изменяется в диапазоне 1.3 – 2.0 Тл, а в тонком слое толщиной 1.0 – 1.5 мм, обращенном к поверхности статора, достигает величины 2.3 Тл. В пределах одного полюсного деления максимум z-компоненты плотности вихревых токов составляет 18·106 А/м2 на внутренней поверхности полого ротора. Определено, что за исключением “краевых” участков ротора, где преобладает поперечная составляющая вихревых токов, а также участков “входа” магнитного потока в ротор, вихревые токи в основном являются аксиальными. Сопоставление результатов измерения напряженности электрического поля на поверхности ротора показало различие данных не более 4%. Предложенная модель позволяет оптимизировать конструкцию преобразователя, в частности, снизить магнитную индукцию в зубцах статора. Научная новизна. Получены численные результаты в виде пространственных картин распределения и графических зависимостей, которые полностью учитывают аксиальную и тангенциальную компоненты электромагнитного поля. Практическая значимость. Рассмотренная конечно-элементная модель может быть использована при анализе электромагнитных полей в электромеханических преобразователях со сложной вторичной частью. Это позволит учесть реальный трехмерный характер поля, вызванный особенностями конструкции и конечными осевыми размерами.This research would not have been possible without the support provided under the state-financed scientific research theme “Development of subsystem for predicting and controlling the dynamics of methane content at mines”. The authors express their gratitude to Professor Mykola Antoshchenko for assistance in conducting the research

Control Strategies for Open-End Winding Drives Operating in the Flux-Weakening Region

This paper presents and compares control strategies for three-phase open-end winding drives operating in the flux-weakening region. A six-leg inverter with a single dc-link is associated with the machine in order to use a single energy source. With this topology, the zero-sequence circuit has to be considered since the zero-sequence current can circulate in the windings. Therefore, conventional over-modulation strategies are not appropriate when the machine enters in the flux-weakening region. A few solutions dealing with the zero-sequence circuit have been proposed in literature. They use a modified space vector modulation or a conventional modulation with additional voltage limitations. The paper describes the aforementioned strategies and then a new strategy is proposed. This new strategy takes into account the magnitudes and phase angles of the voltage harmonic components. This yields better voltage utilization in the dq frame. Furthermore, inverter saturation is avoided in the zero-sequence frame and therefore zero-sequence current control is maintained. Three methods are implemented on a test bed composed of a three-phase permanent-magnet synchronous machine, a six-leg inverter and a hybrid DSP/FPGA controller. Experimental results are presented and compared for all strategies. A performance analysis is conducted as regards the region of operation and the machine parameters.Projet SOFRACI/FU

Comparison and Design Optimization of a Five-Phase Flux-Switching PM Machine for In-Wheel Traction Applications

A comparative study of five-phase outer-rotor flux-switching permanent magnet (FSPM) machines with different topologies for in-wheel traction applications is presented in this paper. Those topologies include double-layer winding, single-layer winding, C-core, and E-core configurations. The electromagnetic performance in the low-speed region, the flux-weakening capability in the high-speed region, and the fault-tolerance capability are all investigated in detail. The results indicate that the E-core FSPM machine has performance advantages. Furthermore, two kinds of E-core FSPM machines with different stator and rotor pole combinations are optimized, respectively. In order to reduce the computational burden during the large-scale optimization process, a mathematical technique is developed based on the concept of computationally efficient finite-element analysis. While a differential evolution algorithm serves as a global search engine to target optimized designs. Subsequently, multiobjective tradeoffs are presented based on a Pareto-set for 20 000 candidate designs. Finally, an optimal design is prototyped, and some experimental results are given to confirm the validity of the simulation results in this paper

On the reliability of electrical drives for safety-critical applications

The aim of this work is to present some issues related to fault tolerant electric drives,which are able to overcome different types of faults occurring in the sensors, in thepower converter and in the electrical machine, without compromising the overallfunctionality of the system. These features are of utmost importance in safety-criticalapplications. In this paper, the reliability of both commercial and innovative driveconfigurations, which use redundant hardware and suitable control algorithms, will beinvestigated for the most common types of fault: besides standard three phase motordrives, also multiphase topologies, open-end winding solutions, multi-machineconfigurations will be analyzed, applied to various electric motor technologies. Thecomplexity of hardware and control strategies will also be compared in this paper, sincethis has a tremendous impact on the investment costs

Asynchronous performance analysis of a single-phase capacitor-start, capacitor-run permanent magnet motor

This work presents a detailed analysis of the asynchronous torque components (average cage, magnet braking torque and pulsating) for a single-phase capacitor-start, capacitor-run permanent magnet motor. The computed envelope of pulsating torque superimposed over the average electromagnetic torque leads to an accurate prediction of starting torque. The developed approach is realized by means of a combination of symmetrical components and d-q axes theory and it can be extended for any m-phase AC motor - induction, synchronous reluctance or synchronous permanent magnet. The resultant average electromagnetic torque is determined by superimposing the asynchronous torques and magnet braking torque effects