Stator Winding Connection Research Articles

Single observer speed sensorless field weakening control of two parallel motors

Two induction motors with parallel connected stator windings supplied by a single inverter (single observer) with a field weakening control system. The objective of this study is to propose a torque production speed sensorless vector control technique for each parallel connected rotor by adding field weakening control to improve the performance of each motor and reducing the number of adaptive observers on each motor to a single observer. Design of a rotor flux-oriented control (RFOC) system. Simulation results with the C-MEX S-function of MATLAB/Simulink 2015b show that the proposed method works better and can be operated at speeds that exceed the nominal speed of the motor.

Design of automatic stator winding connection of induction generator for wind energy conversion system

Design of automatic stator winding connection of induction generator for wind energy conversion system

Design Aspects of Small-Hydropower Plant

Presently, however, Hydroelectric is a source of power that can prove to be available to all, regardless of conditions such as weather. As history showed, a lot of development, as well as alterations, were made to this efficient supply of energy. Hydropower is a positive alternative energy source that nature provides, therefore, its effective usage is not prohibited. Although there are many disadvantages associated with the design and construction of a hydroelectric power plant, the advantageous features are even more enormous. This paper deals with construction and design aspects for the implementation of the small hydroelectric power station. The main parameters can be collected from the site. Then the turbine type and dimensions can be specified. The generator specifications,which is the main part in the system, for hydro-power stations can be obtained from the determination of turbine output power. These specifications involve mainly the rated power in KVA, the type of system, system frequency, the type of stator winding connection, rated load voltage, rated load current, load power factor, generator speed, method of the system cooling, and the generator type of excitation.

Design Alone Is Insufficient to Meet API 541 Fifth Edition Requirements for Reliability: Key Components for Achieving Service Life Conditions

The fifth edition of American Petroleum Institute (API) 541 <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> extended the uninterrupted continuous operation of motors covered by the standard from three to five years and the service life of machines from 20 to 25 years. The standard recognizes that uninterrupted operation for this time period involves factors beyond the vendor’s control. This article provides design, manufacturing, application, and monitoring aspects that will assist the end user in achieving these new service condition requirements. This article discusses the importance of lubrication, ways to maintain low vibration levels from start-up and during operation, accessories to protect vital machine components, the selection of the proper enclosure for an application, stator winding connections, and the proper use of space heaters in the field.

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.

Effect of Winding Connections on Thrust and Current Asymmetry of Linear Induction Machines Considering End Effect

Linear induction motors (LIMs), applied in the field of electromagnetic emission, due to end effect, show the characteristics of thrust rapid decline, and current asymmetry increasing in the process of high-speed movement. This article studies the effect of stator winding connections on thrust and current asymmetry of six-phase shifted 30° LIM considering the static and the longitudinal end effect. The study compares three connections by finite-element analysis, namely, open-end, star, and triangular connections. The theory of symmetric component method is introduced to analyze the asymmetric characteristics caused by the end effect. The output thrust and current asymmetries of the motor under three connection modes are compared in detail. The simulation results show that there is no difference among the three connection modes when only considering static end effect, but once considering dynamic end effect, the output current symmetry of star connection is better than that of the open and triangular connection. Also, Adopting variable slip frequency control method can not only improve output thrust of motor, but also improve current symmetry, especially at high speed obviously, when compared with constant slip frequency control method. The research will be helpful to motor thrust optimization control and winding design in the future.

Investigation of electromagnetic torque production in induction motor during charging operation

Integrated battery chargers (IBCs) provide the flexibility of reusing the electric drive-train components of the electric vehicle (EV) for the charging operation. The purpose of the paper is to reuse its traction inverter and motor windings as rectifier and grid interfacing filter, respectively for charging and keeping rotor standstill without using any external brake. Various winding configurations are developed by splitting the three-phase induction motor (IM) winding into two parts at zero electrical degree to keep the rotor standstill. The different stator winding connections are proposed for IM which restricts the formation of rotating magnetic field (RMF). Cases are categorized into two parts, in the first part, RMF is cancelled to zero and in the other part, RMF is converted into pulsating magnetic field (PMF). Mathematical investigation for torque production in both cases is provided to prove that the proposed winding connections are incapable of developing electromagnetic torque in machine. Mathematical findings are validated by experimentation on split three-phase IM (STP-IM). This analysis is useful in identifying the nature of torque developed in motor during charging operation of EV.

To the choice of the MAGLEV system traction linear synchronous motorstator winding scheme

Aim: Analysis of electromagnetic processes in the linear synchronous traction motor of high-speed ground transport (MAGLEV) and the choice of stator winding connection schemejustification.&#x0D; Methods: An analytical study of theoretical relations.&#x0D; Results: The study found that a two-layer stator winding connection scheme is more preferable&#x0D; Conclusion: A system with a single-layer stator winding connection circuit is characterized by loading excitation solenoids with harmful forces, the inefficiency of their protection from the higher harmonics of the stator winding by choosing the geometry of its coil and solenoid, and the formation of additional colliding force during lateral displacement of the underframe. All these unadvisable effects are absent in a two-layer scheme.

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.

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.

A Universal High-Frequency Induction Machine Model and Characterization Method for Arbitrary Stator Winding Connections

High-frequency modeling of induction machines plays an important role in investigating motor drive electromagnetic interference issues such as stator winding reflected-wave overvoltage and bearing discharging current. Characterization of high-frequency machine models requires measurements of machine's differential-mode (DM) and common-mode (CM) impedances up to tens of MHz. The machine's stator winding connections, e.g., single-, and series-, parallel-winding Y/Δ configurations, influence the measured DM and CM impedances and model parameters. In this paper, a universal high-frequency equivalent circuit model capable of representing induction machines with arbitrary stator winding connections is proposed. The new model features a simple structure with a straightforward characterization method. Specifically, only one stator winding configuration is required for impedance measurements to fully characterize the machine model for arbitrary stator winding connections. The proposed methodology is demonstrated using a 7.5 hp dual-voltage nine-terminal/lead induction machine and a drive system. The simulated DM and CM impedances as well as the motor overvoltages show excellent agreement with the experimental results. The proposed model and characterization method represent significant improvement in terms of accuracy, applicability/generality, and convenience compared to prior conventional models.

Contribution to Offline Measurements of PMSM and SyRM Inductances

The measurement of synchronous inductances for three-phase permanent-magnet (PM) machines is usually performed by means of offline tests connecting the stator windings in different single-phase configurations. A test campaign conducted on different machines has demonstrated that the inductance measurement depends on both the stator winding connection scheme and the rotor position. As a result, a new perspective is provided on the generally adopted methodology for offline measurements of synchronous inductances. In particular, this paper highlights the influence of the connection schemes on the inductance values, using several surface-mounted PM-synchronous and synchronous-reluctance machine examples. This study covers both machines equipped with distributed windings and fractional-slot-concentrated windings.

Study on Different Connection Modes of Dual-Stator Brushless Doubly-Fed Machine Based on Field-Circuit Method

The different winding connection modes of dual-stator brushless doubly-fed machine (DSBDFM) are investigated to ensure the electromagnetic characteristics consistency of outer and inner stator. The electromagnetic characteristics consistency is not only required that the electromotive force (EMF) amplitude and phase match the requirements of outer and inner stator winding connection mode, but also the number of parallel branches of winding should be considered to avoid the circular current and phase difference. This paper proposes a method for the number of parallel branches of winding, which is helpful to determine the number of parallel branches of two sets of winding with different pole pairs number in stator slots and ensure the EMF amplitude and phase of per branch winding. The field-circuit method (FCM) is used to analyze the different connection modes of DSBDFM, such as series, parallel, series and parallel. The finite element method was confirmed agreement with the FCM, indicating the validity and rationality of FCM.

Effects of Winding Connection on Performance of a Six-Phase Switched Reluctance Machine

This paper investigates the effect of the stator winding connection on the performance of a six-phase switched reluctance machine (SRM). Five winding connection types are proposed for the machine. Finite element analyses (FEAs) of flux distribution, output torque, and core losses are presented under single-phase and multiphase excitation for each connection and the results are used to compare the average torque and torque ripple ratio characteristics and to develop understanding of the respective contributions of mutual inductance in the torque development. Experimental tests on a six-phase conventional SRM verify the torque performance and mutual inductance effects of the different winding connections. An optimum winding configuration for a six-phase SRM is proposed.

Dynamic Modeling of a Five-Phase Induction Machine With a Combined Star/Pentagon Stator Winding Connection

The combined star/pentagon connection of five-phase induction machines was recently demonstrated as a promising compromise between conventional star and pentagon connections. It combines the advantages of both star and pentagon connections without any additional hardware for winding changeover. This connection is based on two five-phase single layer concentrated winding sets shifted in space by π/10 and connected in a combined star/pentagon configuration to provide five-phase terminals. Since the combined star/pentagon connected induction machine is fundamentally an asymmetrical ten-phase machine, the machine mathematical model possesses additional subspaces, which affect the behavior of the machine especially under open line conditions. Starting from the conventional five-phase and m -bar squirrel cage induction machine model, the phase-variable model of the combined star/pentagon connection is introduced in this paper. The corresponding equivalent dq model with five decoupled subspaces, which can account for air gap harmonics up to ninth order, is then derived. Finally, it was shown that the machine model could be simply approximated with only two subspaces similar to a conventional five-phase induction machine with sinusoidally distributed winding, where the flux produced by the nonfundamental subspace could be neglected. The model is verified using a 1 kW prototype five-phase induction machine.

Steady-State Mathematical Modeling of a Five-Phase Induction Machine With a Combined Star/Pentagon Stator Winding Connection

This paper presents the steady-state mathematical model of a five-phase induction machine with a combined star/pentagon connection. The connection splits the stator winding into two five-phase windings displaced in space by $\pi$ /10 and connected in a combined star/pentagon configuration. Recent work limited to an experimental investigation demonstrated that the connection possesses improved fault tolerance when compared to a conventional star-connected stator, as well as avoids the pentagon connection problems. Although the machine has five-phase terminals, it is intrinsically an asymmetrical ten-phase machine, which introduces additional subspaces in the machine's mathematical model. In order to theoretically investigate and thoroughly assess this connection against conventional connections, this paper introduces the steady-state mathematical model based on vector space decomposition and symmetrical component theory. Finite-element analysis is first used to investigate the different harmonic current components induced in the cage rotor circuit, upon which the effect of different subspaces can be clarified and the required transformation matrix from phase variables to their sequence components can be derived. The model is verified using a 1-kW prototype five-phase induction machine.

Effect of Multilayer Windings With Different Stator Winding Connections on Interior PM Machines for EV Applications

The interior permanent magnet (IPM) machine equipped with a fractional-slot concentrated winding (FSCW) has met an increasing interest in electric vehicle applications due to its higher power density and efficiency. Torque production is due to both PM and reluctance torques. However, one of the main challenges of FSCWs is their inability to produce a high-quality magnetomotive force (MMF) distribution, yielding undesirable rotor core and magnet eddy-current losses. Literature shows that the reduction of low-order space harmonics significantly reduces these loss components. Moreover, it has been previously shown that by employing a higher number of layers, although causing some reduction in the winding factor of the torque-producing MMF component, both machine saliency and reluctance torque components are improved. Recently, a dual three-phase winding connected in a star/delta connection has also shown promise to concurrently enhance machine torque of a surface-mounted PM machine while significantly reducing both rotor core and magnet losses. In this paper, a multilayer winding configuration and a dual three-phase winding connection are combined and applied to the well-known 12-slot/10-pole IPM machine with v-shaped magnets. The proposed winding layout is compared with a conventional double-layer winding, a dual three-phase double-layer winding, and a four-layer winding. The comparison is carried out using 2-D finite-element analysis. The comparison shows that the proposed winding layout, while providing similar output torque to a conventional double-layer three-phase winding, offers a significant reduction in core and magnet losses, correspondingly a higher efficiency, improves the machine saliency ratio, and maximizes the reluctance toque component.

Influence of mover yoke and winding connections on unbalanced normal force for double‐sided linear switched reluctance machine

Due to the manufacturing inaccuracies or wear, the mover eccentricity of the double-sided linear switched reluctance machine (DLSRM) is practically inevitable, which gives rise to undesirable unbalanced normal force (UNF). This study investigates the UNF reduction methods in the eccentric DLSRM. According to the finite element analysis and magnetic circuit analysis, the flux distributions and the UNF of the healthy and eccentric DLSRM are compared, and it is proved that removing the mover yoke can alleviate the UNF in the eccentric situation. Furthermore, the effects of the stator winding connections on UNF are analysed via a transient two-dimensional finite element model. It shows that the UNF can also be reduced by connecting the coils of the windings in parallel. For verifying the two proposed methods, a prototype experimental platform is established, and the experimental results validate the analyses.

Improved SVPWM vector selection approaches in OVM region to reduce common-mode voltage for three-level neutral point clamped inverter

Abstract Multilevel inverters (MLIs) have an essential portion in industrial applications. Eventhough there are various elementary developments in MLI and its pulse width modulation (PWM) control strategies, unfortunately those strategies are least bothered about the common mode voltage (CMV). The CMV appears at the neutral point of the motor’s star connected stator windings with respect to the source ground. This study proposes PWM schemes for three level diode clamped multilevel inverter (DC-MLI) which use an unpretentious switching sequence to determine the triangle for maximum output voltage and minimum CMV in entire modulation range. Here two types of approaches are proposed: (i) Partial elimination SVPWM (PE-SVPWM) and (ii) Full elimination (FE-SVPWM). The proposed strategies suggest switching selection by using the control degree of freedom available in SVPWM without affecting the inverter output voltage. As a result, CMV reduction and elimination with maximum output voltage and better THD is achieved. The proposed PWM approaches can be extended for any number of levels. The theoretical study, the MATLAB/Simulink software based computer simulation and Field Programmable Gate Array (FPGA) SPARTAN-III-3AN-XC3S400 processor supported hardware corroboration have shown the superiority of the proposed technique over the existing SVPWM schemes.

An Improved Fault-Tolerant Five-Phase Induction Machine Using a Combined Star/Pentagon Single Layer Stator Winding Connection

One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower derating factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower derating factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification.