Stator Winding Configuration Research Articles

Effect of stator winding chording on the performance of five phase synchronous reluctance motor

The effect of winding chording on five-phase synchronous reluctance motor (SRM) modelled in phase variables is presented. The stator winding configuration is shifted a pole pitch from a full-pitch configuration to a 54 degrees over-full-pitched configuration incorporating the effect of 3rd harmonic of the air-gap magneto-motive force in the inductance equations. The models are monitored on starting, synchronism, loading, faults and loss of synchronism. These are considered simultaneously with vector potential, rotor speed, air-gap flux linkage and winding current. The phase variable (analytical) models have been simulated by using MATLAB/Simulink software while ANSYS Maxwell software has been used to simulate the finite element model (FEM) of the motor for corresponding chording ranges for comparison on direct online starting (DOL). Under all conditions considered in the work, the detailed results are presented and very close similarity is observed between the analytical and the nearly ideal FEM model for all chording ranges and the similarity is enhanced with increase in chording angle.

Analysis of a Three-Phase Induction Motor with a Double–Triple-Layer Stator Winding Configuration Operating with Broken Rotor Bar Faults

This paper presents the performance analysis of a three-phase squirrel cage induction motor (SCIM) with a double–triple-layer (DTL) stator winding configuration operating with broken rotor bar (BRB) faults. The effects of BRB faults on the performance of specific parameters are analyzed under a steady-state regime. The SCIM is modeled using the two-dimensional finite element method (FEM) to study electromagnetic performance under healthy and BRB faulty conditions. To validate the finite element analysis (FEA) results, a prototype of an SCIM with a DTL stator winding configuration is tested for performance evaluation under healthy and BRB faulty conditions. The FEA and experimental (EXP) results of the SCIM with a DTL stator winding arrangement are compared with the results of the SCIM with a conventional double-layer (CDL) stator winding configuration. FEA and EXP results evidenced that the SCIM with a DTL stator winding configuration mitigates some of the adverse effects introduced by the BRB faults compared to the SCIM with a CDL stator winding of the exact specifications. Under loaded conditions, the SCIM with a DTL stator winding configuration reduced the magnitudes of the twice slip frequency sidebands caused by BRB faults from ±1.2 Hz for the SCIM with a CDL stator winding arrangement down to ±0.2 Hz and ±0.36 Hz when operating with 3BRB and 6BRB faults, respectively. The results also indicate that the SCIM with a DTL stator winding configuration has reduced the decibel sideband magnitude by 7.5 dB and 8 dB for unloaded and loaded conditions, respectively. This premise has positioned the SCIM with a DTL stator winding configuration as a strong candidate in applications where BRB faults are frequent, and the motor may be required to continue operating with a BRB fault until scheduled maintenance is in effect.

Performance improvement of 36‐slot 6‐terminal induction motor drive using pole phase modulation with higher slot per pole per phase

SummaryElectric vehicles (EVs) are getting imperative with passing time due to depleting fossil fuel resources and worsening pollution scenario. Induction motors (IMs) are a promising alternative to the conventional drive systems due to its inherent advantages. However, an efficient geared operation similar to internal combustion engine (ICE) vehicles is essential for wider adoption of the IM drive in EVs. Pole phase modulation technique helps achieve variable speed and torque combinations analogous to geared operation in IM. Performance of the IM drive can be improved by altering the stator winding configuration to achieve high slot per pole per phase, lesser leakage reactance, and lower DC link voltages. A single layered distributed winding is proposed in this work to achieve the above objectives. The proposed winding is first simulated using Maxwell‐2D and Finite Element Analysis (FEA) that are performed to understand the performance characteristics of IM drive with proposed winding scheme. The hardware implementation of the similar setup is done, and the tests are carried out to validate the simulation results. A 3HP, 36‐slot, 6‐terminal IM was fabricated for this purpose which was fed by the microcontroller based 6‐leg inverter for stator winding excitation. This helps to achieve low pole (6‐phase/2‐pole) and high pole (3‐phase/4‐pole) modes of operation to simulate a 2‐geared ICE performance. The study proved that high torque driving requirements can be fulfilled by a low pole operation while cruising requirements are met with a high pole operation. It also showed that the constant power region increases along with the efficiency contours plotted against the torque‐speed characteristics.

Üç Fazlı Bir Asenkron Motorun Çeşitli Bobin Adım Biçimi ile Performans ve Harmonik Analizi

In this work, analyses of the effect of full-, under-, and over-pitched stator winding configurations on the efficiency, output power, torque characteristics, and current and voltage harmonic components are carried out on a three-phase, squirrel cage induction motor. Performance analyses have been performed both via Ansys/RMxprt and Maxwell/2D software by modelling the stator winding with coil pitches of 100°, 120°, 140°, 160°, 180°, 200°, 220°, 240°, and 260°. Current and voltage harmonics analyses have been performed in Matlab using the data obtained from Maxwell/2D simulations. Maxwell/2D results showed that the maximum efficiency is attained at 200° over-pitched configuration, which is 0.73% higher than the efficiency when the motor is full-pitched. The maximum output power and torque are attained at 240° over-pitched configuration, which is 7.96% and 7.45% more than the power and torque obtained when the motor is full-pitched, respectively. Harmonic analysis results showed that both under-pitched and over-pitched coils can be used to eliminate harmonics in the current and voltage waveforms. However, over-pitched coils performed better in eliminating the phase current harmonics. The minimum total harmonic distortion (THD) of the phase current and induced voltage are reached at 260° over-pitched and 120° under-pitched configurations, which is 52.39% and 74.36% lower than the THD when the motor is full-pitched, respectively. Over-pitched coils provide slightly higher efficiency, output power, and torque than the under-pitched coils. There is no unique coil pitch configuration to eliminate all harmonic components. Therefore, in order to eliminate a specific harmonic component, a specific coil-pitch must be applied.

Eddy current loss estimation for direct drive wind turbine generators with superconducting excitation winding by numerical and analytical models

AbstractDirect drive wind turbine generators with superconducting excitation winding are studied with focus on the electromagnetic damper design. A semi‐analytical eddy current model is built for parametric design studies based on a vector potential approach. The considered generators employ open stator slots and exhibit strong saturation effects, so that an analytical expression for the source terms is not adequate. Whilst the field equations are solved analytically, an equivalent current loading, accounting for slotting effects and saturation, is obtained by magnetostatic models applying the 2D finite element method (FEM). The proposed framework for the extraction of the current loading is universal and may also be applied to other machine types (e.g., permanent magnet synchronous machines, [PMSM]). In relation to transient FEM models, a considerable time‐saving can be achieved, which is particularly beneficial in case of large models, for example, in case of fractional slot windings or intermittent feeding schemes. The eddy current loss in warm and cold rotor parts in a direct drive generator in the 7 MW power class are computed with the semi‐analytical and transient 2D FEM models under variation of the damper geometry and the stator winding configuration. Minimum damper dimensions as well as constraints regarding applicable stator windings are derived.

A Permanent Magnet Synchronous Spherical Motor for High-Mobility Servo-Actuation

The development of direct-drive spherical motors offers a potential solution to the limitations of conventional multiple degree-of-freedom (DOF) actuators, which typically utilize single-DOF joints (rotational and/or prismatic), arranged in series or parallel and powered by multiple single-DOF actuators. These configurations can be accompanied by kinematic singularities, backlash, limited power density and efficiency, and computationally expensive inverse kinematics. This paper details the design, fabrication and experimental testing of permanent magnet synchronous spherical motors (PMSSM) for multi-DOF servo-actuation. Its stator-pole arrangement is based on a Goldberg polyhedron, with each pole comprised of hexagonal or pentagonal inner and outer plates. The stator geometry and winding configurations are optimized using electromagnetic finite element analysis. A custom-made controller board includes a microcontroller, servo drivers, a wireless serial interface, and a USB PC interface. Angular orientation is sensed using an inertial measurement unit in wireless communication with the microcontroller. A PID controller is implemented and demonstrated for time-varying reference trajectories.

Study of current ripple characteristics of inverter-fed multiple three-phase AC motors

The need of higher power and more reliable applications have promoted the use of multiphase alternating current (AC) drives. Mostly the motors are used in wide speed operation range. To control the motors, in the low speed region the motors are operated under pulse width modulation (PWM) mode and in the high speed region, they use square wave mode. In this paper, the current ripple characteristics of inverter-fed multiple three-phase AC motors that are operated under dual mode operation (PWM and square wave modes) are investigated. The optimal motor stator winding configuration will be optimized from the viewpoint of inverter input and motor current ripples. Six-phase motor is used as the representative of even-phase motors and nine-phase motor for odd-phase motors. It is found that nine-phase motor is better than six-phase motor if dual mode operation is desired. Experimental results are incorporated to support the analytical results.

A Novel Sub-Harmonic Synchronous Machine Using Three-Layer Winding Topology

This paper proposes a novel brushless synchronous machine topology that utilizes stator sub-harmonic magnetomotive force (MMF) for desirable brushless operation. The sub-harmonic MMF component that is used in this novel topology is one fourth of the fundamental MMF component, whereas, in previous practices, it was half. To achieve the brushless operation, the novel machine uses a unique stator winding configuration of two sets of balanced 3-phase winding wound in 3 layers. For the rotor, additional winding is placed to induce the sub-harmonic component to achieve the brushless excitation. Unlike its predecessors, it utilizes maximum allowable space in the stator to house conductors in all of its slots. To implement the topology, 8-pole, 48-slot sub-harmonic brushless synchronous machine model has been designed. A 2-D finite element analysis (FEA) is used to simulate and validate the performance of the novel machine as a motor. The proposed topology shows better average torque than the existing sub-harmonic wound rotor brushless synchronous machine topologies.

Frequency Analysis of Partial Short-Circuit Fault in BLDC Motors with Combined Star-Delta Winding

This paper analyses the condition of a partial short-circuit in a brushless permanent magnet motor. Additionally, the problem was analysed for three stator winding configurations: star, delta and star-delta connection. The paper presents an original mathematical model allowing a winding configurations to be analysed. What is more, the said mathematical model allows taking account of the partial short-circuit condition. Frequency analysis (Fast Fourier Transform—FFT) of the artificial neutral point voltage was proposed for the purpose of detecting the partial short-circuit condition. It was demonstrated that a partial short-circuit causes a marked increase in the diagnostic frequencies of the voltage signal. The proposed brushless permanent magnet motor diagnostic method is able to detect the fault regardless of the stator winding configuration type.

Optimization of Air Gap Length and Capacitive Auxiliary Winding in Three-Phase Induction Motors Based on a Genetic Algorithm

There is a necessity to design a three-phase squirrel cage induction motor (SCIM) for high-speed applications with a larger air gap length in order to limit the distortion of air gap flux density, the thermal expansion of stator and rotor teeth, centrifugal forces, and the magnetic pull. To that effect, a larger air gap length lowers the power factor, efficiency, and torque density of a three-phase SCIM. This should inform motor design engineers to take special care during the design process of a three-phase SCIM by selecting an air gap length that will provide optimal performance. This paper presents an approach that would assist with the selection of an optimal air gap length (OAL) and optimal capacitive auxiliary stator winding (OCASW) configuration for a high torque per ampere (TPA) three-phase SCIM. A genetic algorithm (GA) assisted by finite element analysis (FEA) is used in the design process to determine the OAL and OCASW required to obtain a high torque per ampere without compromising the merit of achieving an excellent power factor and high efficiency for a three-phase SCIM. The performance of the optimized three-phase SCIM is compared to unoptimized machines. The results obtained from FEA are validated through experimental measurements. Owing to the penalty functions related to the value of objective and constraint functions introduced in the genetic algorithm model, both the FEA and experimental results provide evidence that an enhanced torque per ampere three-phase SCIM can be realized for a large OAL and OCASW with high efficiency and an excellent power factor in different working conditions.

Eccentricity fault detection in brushless doubly fed induction machines

A new fault diagnosis method for detecting the rotor eccentricity faults including static, dynamic and mixed eccentricity is proposed for brushless doubly-fed induction machines (BDFIMs). BDFIMs are attractive alternatives for the conventional doubly-fed induction generator (DFIG) for offshore wind power generation; therefore, paying attention to their fault detection is essential. Existing fault detection methods for conventional induction machines cannot be directly applied to the BDFIM due to its special rotor structure and stator winding configurations as well as complex magnetic field patterns. This article proposes a novel fault detection method based on motor current signal analysis to determine stator current harmonics, induced by the nested-loop rotor slot harmonics (NRSHs), as fault indices. The analysis is performed under healthy conditions and with different types of rotor eccentricity. Finally, a sensitivity analysis is carried out to confirm the practicability of the proposed technique with various fault intensities and load conditions. Analytical winding function approach, finite element analysis and experimental tests on a prototype D180 BDFIM are used in this study to validate the proposed fault detection technique.

Study and Active Enhancement by Converter Reconfiguration of the Performance in Terms of Stator Copper Loss, Derating Factor and Converter Rating of Multiphase Drives Under Two Open Legs With Different Stator Winding Connections

Multiphase machines offer inherent tolerance to faults such as open converter legs (OCLs), which are especially frequent. Because of this reason, they are particularly attractive for applications where fault tolerance is important, such as offshore wind energy or aerospace, naval and military vehicles. It has been previously shown that, under an OCL, certain stator winding configurations (SWCs) different from star yield smaller stator copper loss (SCL) and larger maximum achievable torque (MAT) than star SWC for the same torque command and machine. This advantage comes just at the expense of a moderate increase in converter rating. However, only the case of single OCL was studied in general. The SCL, MAT and required converter rating for two OCLs are currently unknown for different combinations of phase number, faulted legs and SWCs. Actually, under two OCLs (unlike for one OCL) it may be possible to actively modify the order of the faulted/healthy legs to enhance the performance in these terms, but this possibility has not been studied so far in spite of its potential. This paper addresses the postfault performance of multiphase drives with two OCLs, for various SWCs. The MAT (derating factor), SCL and necessary converter rating are assessed in numerous possible scenarios. The most convenient alternatives are established. Most importantly, in view of the conclusions of this analysis, a novel method is proposed to improve substantially the MAT and SCL by actively altering the connections between the converter and machine terminals. Experimental results with six-phase and twelve-phase setups are provided.

Bi-Furcated Stator Winding Configuration in Three-Phase Induction Generators for Wind Power Generation

The concerns over the increase in carbon footprints and global climatic changes have given momentum to find ways that reduce the use of fossil fuels to generate electricity. Offshore and onshore windmills for electricity generation are viable options for bulk power generation. A wind generation system has a variable frequency variable voltage supply at the induction generator terminals in response to the changes in the wind velocity and in turn, the speed of the wind turbine. There is a need for an additional power electronic interface to maintain the frequency and voltage at the terminals of the wind generator constant. This paper introduces a novel three-phase Bifurcated Winding Induction Generator (BWIG) comprising a bifurcated set of stator windings. A prototype model has been developed by bifurcating the stator windings of a three-phase induction machine. One part of the winding acts as the excitation winding, and the other half is used as output winding capable of producing three-phase voltages at a constant frequency at all speeds of the prime over. The machine is tested for sub and super synchronous speeds and the characteristics plotted. The flux analysis of the machine is simulated using Ansys Maxwell software. The voltage is controlled by a simple off-on control implemented using a digital controller, TMS320F28335.

A Novel Matrix Transformation for Decoupled Control of Modular Multiphase PMSM Drives

When multiphase drives are used for specific applications, the modular solutions are preferred as they use consolidated power electronics technologies. The literature reports two modeling approaches for multiphase machines having a modular configuration of the stator winding. The first approach is the vector space decomposition (VSD) that models the energy conversion as for an equivalent three-phase machine. The main alternative to the VSD is the multistator (MS) modeling that emphasizes machine modularity in terms of torque production. Both approaches have advantages and disadvantages for multiphase machines with a modular structure. Therefore, this article aims to combine the VSD and MS approaches, defining a new matrix transformation and, hence, developing a new modeling approach for multiphase machines with a modular structure. The proposed transformation allows a decoupled and independent torque control of the sets composing the machine, preserving the torque regulation's modularity. Together with a new vector control scheme, it has been applied to a modular permanent magnet synchronous machine (PMSM) with a nonstandard spatial shift between windings. Experimental results are presented for a nine-phase PMSM prototype with a triple-three-phase stator winding configuration.

Induction Motor Fault Diagnosis Based on Zero-Sequence Current Analysis

This paper presents some considerations regarding the application of the stator zero-sequence current component (ZSC) in the fault detection of cage induction machines, including the effects of magnetic core saturation. Faults such as rotor cage asymmetry and static, dynamic, and mixed eccentricity were considered. The research started by developing a harmonic motor model, which allowed us to obtain a voltage equation for the zero-sequence current component. The equation allowed us to extract formulas of typical frequencies for particular fault types. Next, in order to verify the effectiveness of ZSC in induction motor fault diagnosis, finite element calculations and laboratory tests were carried out for the previously mentioned faults for delta and wye connections with neutral wire stator winding configurations.

Comparison of Different Stator Winding Configurations of Fully High-Temperature Superconducting Induction/Synchronous Motor

This paper compared the performance of different stator winding configurations of a fully high-temperature superconducting induction/synchronous motor (HTS-ISM). The stator winding and squirrel-cage winding were fabricated by using Bi-2223 tapes. The performance of fully HTS-ISM with concentrated winding, distributed winding and toroidal winding were compared based on Finite Element Analysis (FEA), respectively. Both of the rotating performance and current transport property of HTS tapes are considered. It is found that with toroidal winding, the fully HTS-ISM has larger torque density, lower torque ripple and larger current transport property of HTS tapes.

Integrated Battery Charger for EV by Using Three-Phase Induction Motor Stator Windings as Filter

This article presents an on-board charger for the electric vehicles (EVs) by integrating the drive-train components into the charging process. The stator windings of three-phase induction motor (IM) can be used as a grid interfacing inductor with the constraint that the rotor should be in the stationary position during the charging mode. This article proposes the stator winding configurations of three-phase IM split into two equal parts at zero electrical degree for the on-board integrated battery charger. The effective filtering with these two three-phase windings combination, either in series or parallel while the rotor is in a stationary position, is analyzed. The equivalent inductance provided by the stator windings for filtering is increased by generating the pulsating magnetic field (PMF) in the motor. However, it results in the unbalanced impedances in filter causing odd harmonics in the grid current. This is resolved by using a modified double synchronous reference frame control algorithm, which maintains the balanced current operation with the unity power factor at the grid interface during the charging mode. This configuration is obtained by using the existing three-phase-based drive-train components, thereby providing the saving in space and reducing the weight of EV. Experimental results for the proposed winding configurations are presented with filter losses and system efficiency.

Comparison of stator winding connections in multiphase drives under healthy operation and with one open converter leg

Multiphase machines with symmetrical windings offer various stator winding configurations (SWCs). It is known that, for a given five-phase machine, the pentagon SWC implies, compared with star, smaller voltage rating and greater current rating of the converter. For healthy conditions, the stator copper loss (SCL) and maximum achievable torque (MAT) are almost identical for both SWCs, provided such converter-rating adjustments and negligible circulating currents. Regarding the operation of five-phase machines under open converter leg (especially common fault), the pentagon SWC attains lower SCL (for given torque) and larger MAT than star. However, it is unknown if these characteristics hold (and to which extent) for other phase numbers and SWCs. This study compares for multiple phase numbers the SWCs in terms of converter rating, MAT and SCL, under healthy operation and with an open converter leg. Most importantly, it is shown that, for phase numbers higher than five (the case previously studied), the improvement in performance (especially postfault MAT) by resorting to SWCs other than star can be much larger than for five phases, and it is thus of considerable interest. The most convenient alternatives (often different from the five-phase case) are established. Experimental results with two multiphase drives are included.

Decoupled and Modular Torque Control of Multi-Three-Phase Induction Motor Drives

In recent years, the development of multi-three-phase drives for both energy production and transportation electrification has gained growing attention. An essential feature of the multi-three-phase drives is their modularity since they can be configured as three-phase units operating in parallel and with a modular control scheme. The so-called multi-stator modeling approach represents a suitable solution for the implementation of modular control strategies able to deal with several three-phase units. Nevertheless, the use of the multi-stator approach leads to relevant coupling terms in the resulting set of equations. To solve this issue, a new decoupling transformation for the decoupled torque control of multi-three-phase induction motor drives is proposed. The experimental validation has been carried out with a modular power converter feeding a 12-phase induction machine prototype (10 kW, 6000 r/min) using a quadruple three-phase stator winding configuration.

Wide-Speed Range Operation of PM Vernier Machines Using Wye and Wye-Delta Winding Configurations

This paper proposes two permanent magnet vernier machines (PMVM) operation modes, for wide-speed and high efficiency operation. In mode-1, the machine operates as a conventional PMVM with a wye connected stator winding mode. In mode-2, the machine stator winding is switched to a wye-delta winding mode. Contrary to the existing dual-inverter PMVM topology with two additional bidirectional thyristor switches, the proposed topology utilizes a single inverter with six additional bidirectional thyristor switches to change mode. A theoretical discussion of the proposed idea is further verified via finite element analysis (FEA) simulations. The basic electromagnetic characteristics, such as the flux linkage, back electromotive force, torque, and phase voltages of the machine are investigated using wye and wye-delta stator winding configurations, and subsequently, compared with the existing topology that used a dual-inverter PMVM. The FEA results show that the proposed PMVM has low over-all losses, consequently resulting in improved efficiency compared to the existing topology. The speed increases by almost 9 times using the proposed single-inverter PMVM. Transient analysis using FEA is also conducted in this paper.