Split Winding Research Articles

Realization of a Three-Switch Leg/Phase Inverter for Nine-Phase Variable Pole– Phase Induction Machine With Phase Grouping Concepts

In this paper, a 3-switch leg/phase inverter topology is realized for 9-phase variable pole-phase induction motor (9Ph-VPIM) drives. The 3-switch legs (3SL) in the proposed inverter are controlled with two non-intersecting phase shifted references to achieve a 3-level voltage excitation for each phase winding. These two non-intersecting references per leg limit the possible modulation index (MI) and may require a higher DC link voltage. The split winding concept and the phase grouping solutions are used to enhance the MI. In the split winding concept, phase winding of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2n</i> pole machine is divided into <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> number of distinct windings and excited with the same voltage for attaining a uniform air gap flux. These coils are called cognate voltage coils (CVC). With these CVCs, different possible groupings are proposed to enhance the MI of a proposed 3SL/phase inverter. The symmetrical and efficient phase grouping solutions are analyzed and tested with an improved modulation index. Moreover, the proposed 9Ph-VPIM drive is controlled with carrier-based 3-φ SVPWM to further enhance the DC link voltage utilization. The proposed inverter will feed the effective phase by a 3-level voltage with suppressed harmonics resulting in a superior torque ripple. The proposed 3SL/phase inverter fed 5-hp 9Ph-VPIM drive is validated with the experimental prototype.

Application of Active Disturbance Rejection in a Bearingless Machine with Split-Winding

In this paper it is proposed the displacement control of a bearingless induction machine (BIM) with split winding and optimized drive structure using Active Disturbance Rejection Control (ADRC). Considering that the BIM is a multivariable, nonlinear, and time-varying system with coupled variables, advanced control techniques can be useful in order to make the system operate efficiently and with good dynamic performance. The ADRC considers the total disturbance, composed of unmodeled dynamics, nonlinearities, uncertainties, and load variations, as an extended state and estimates it in real-time through a state observer. This increases the overall robustness of the control system to disturbances of different natures. The application of the ADRC technique on the radial position control of the BIM used in this work showed that a Linear version of ADRC is not able to compensate for radial load disturbances but this drawback can be solved by the use of a nonlinear observer in the ADRC structure. Besides that, both control versions of the ADRC were able to make stable the naturally unstable radial displacement of the machine’s rotor.

A Winding Structure of Air-Core Planar Inductors for Reducing High-Frequency Eddy Currents

High-frequency converters with high power density have shown promise in recent years. Air-core planar inductors built with printed circuit boards can eliminate problems associated with the use of magnetic materials, such as iron loss and magnetic saturation. However, conventional air-core planar inductors suffer from eddy current loss. Eddy currents affect the resistance and inductance of the inductor. This article proposes a stranded wire structure to reduce eddy currents more than that in the conventional spiral wire structure. Eddy currents can be reduced by splitting the windings as well as currents of each split winding are balanced in the proposed structure. Seven types of air-core planar inductors were built, and their resistances, inductances, and impedances were measured to evaluate the effects of different structures on eddy currents. Furthermore, the temperature distribution of the planar inductors was measured while supplying a sinusoidal voltage with a power amplifier. The experimental results demonstrate the usefulness of the proposed stranded wire structure. Furthermore, the experimental result shows that the stray capacitance of the inductor can be reduced as a by-product of the proposed stranded wire structure.

An Unequal Split Dual Three-Phase PMSM With Extended Torque-Speed Characteristics for Automotive Application

High gradability and wide operating speed range are critical requirements for heavy-duty trucks and off-road electric vehicles. The motor power rating used for such applications can be reduced by selecting a motor with a wide constant power speed range (CPSR). However, permanent magnet synchronous motors (PMSMs) with wide CPSR have limited overloading capability. The operating speed range, as well as the overloading capability, can be improved by increasing the base speed of a low CPSR three-phase PMSM, which results in overdesign. Further, using multigear transmission to achieve a wide operating speed range with a low power motor increases system weight, drivetrain complexity, and maintenance requirement. This article proposes a dual three-phase interior PMSM with an unequal split winding configuration and zero degree winding displacement (uneq0-PMSM) to extend the constant power region and improve the overloading capability without any machine overdesign. The winding split ratio for the proposed configuration is decided to achieve the desired torque-speed characteristic shape for a given requirement. Further, a transition algorithm for smooth changeover between two-winding operation during low-speed and one-winding operation for high-speed is also proposed. The proposed concepts are experimentally validated on a 1.5-kW uneq0-PMSM with 1:3 winding split ratio.

Analysis and Comparison of Series Resonant Converter With Embedded Filters for High Power Density DCX of Solid-State Transformer

A series resonant converter (SRC) operating as a DC transformer (DCX) is a candidate for the isolated bidirectional DC/DC converters of solid-state transformers (SSTs). However, the input/output current ripple of the SRC is relatively high, which requires bulky parallel capacitors and low-pass filters such as C/LC filters. These additional components reduce the power density. In addition, to operate an SRC as a DCX, a small resonant inductance is desired to reduce the voltage gain variation and achieve a faster transient response. To resolve these problems, a SRC with embedded filters is studied. Adding a clamping capacitor between split transformers not only significantly reduces current ripples and the harmonic components of the input/output currents but also connects resonant inductors in parallel to reduce the equivalent resonant inductance. In addition, dividing the resonant current into two split windings reduces the RMS current of the transformer. This paper presents a detailed analysis, a design methodology, and a comprehensive comparison with the conventional half-bridge CLLC converter with C/LC filters. 1-kW prototypes with a 600-V input voltage and 200-V output voltage demonstrate the superiority of the proposed converter; the second harmonic of the output current was significantly suppressed by 19.3 dB compared with that of the conventional converter with the same power density. The loss breakdown showed the proposed converter mitigated copper loss by 9.47% and eliminated the losses of the filter and DC-link capacitors. The prototype of the proposed converter had the highest efficiency of 95.4% at full-load among prototypes.

A Novel Driving Scheme for Three-Phase Bearingless Induction Machine with Split Winding

In order to reduce the costs of implementing the radial position control system of a three-phase bearingless machine with split winding, this article proposes a driving method that uses only two phases of the system instead of the three-phase traditional one. It reduces from six to four the number of inverter legs, drivers, sensors, and current controllers necessary to drive and control the system. To justify the proposal, this new power and control configuration was applied to a 250 W machine controlled by a digital signal processor (DSP). The results obtained demonstrated that it is possible to carry out the radial position control through two phases, without loss of performance in relation to the conventional three-phase drive and control system.

Current modeling in a bus packet of a high-current system

A graphoanalytic method for determining the highcurrent system resistances and a mathematical model of a single-phase furnace transformer with a split secondary winding are developed for modeling currents in a transformer and a high-current system bus package in case of short circuit and opening of flexible connections. Experiments have proved the adequacy of the proposed method. The simulation error does not exceed 10 %. Keywords: single-phase transformer, split winding, short circuit, high-current system, opening, resistance, mathematical model, modeling. timokvey@mail.ru

The design and practical implementation of a six-phase induction motor

This thesis presents a re-designed conventional three phase 5-hp squirrel cage, 4-pole, 48 slots induction motor to a six-phase induction motor (SPIM). It also presents the in-depth of a single layer winding of a three-phase motor that was re-design to the six-phase split winding layout which was practically explained to the understanding of both the engineers and the technicians who normally find it difficult with windings of electrical machines. The optimized re-designed SPIM is presented in the MATLAB/Simulink environment to perform a comparative assessment of the different phase loss scenarios of the six-phase configuration with respect to the six-phase healthy case and its conventional three-phase induction motor. The result shows a comparative benefit of the six-phase induction motor over the three-phase induction motor; in such that in the near future because of its effective way to provide a higher reliability and sustainability under the loss of phase/phases condition it will be practically applied in the power driven devices/machines like in the area of Electric Vehicles, etc.

Design of an Isolated Bidirectional DC–DC Converter With Built-in Filters for High Power Density

This article aims to realize an isolated dc-dc converter with high power density, high power efficiency, and low noise performance. Although a dual-active-half-bridge (DAHB) converter can achieve high efficiency, it requires input and output low-pass filters to suppress the operational ripple current and switching noise. Owing to the volume of the filters, a DAHB converter cannot be implemented with high power density. This article presents a design theory for a novel isolated bidirectional dc-dc converter with built-in filters. The proposed converter is derived from a DAHB converter and can eliminate the input and output filters via split windings and tank capacitors; the principle of elimination is based on LC low-pass filter function and zero-ripple-current operation. As the number of transistors, capacitors, and magnetic cores of the proposed converter are equal to those of the DAHB converter, the application of the proposed converter allows volume reduction by eliminating the filter components at the input and output ports. Theoretical equations are derived to design a power flow control function and a filter function simultaneously. Finally, prototypes of a DAHB converter and the proposed converter are constructed for comparison. The results demonstrate that the input port noise of the proposed prototype is lower than that of the DAHB prototype by 10 dB (peak) over 1 MHz, and the proposed approach can achieve a significant improvement in efficiency.

Design of coupled inductors using split winding scheme for bridgeless SEPIC

A bridgeless single-ended primary inductance converter (SEPIC) is a highly preferred single-stage front-end AC–DC converter for applications requiring a wide variation of DC voltage because it also gives improved performance in terms of the quality of supply current. This study presents the design of coupled inductors for the bridgeless SEPIC using the split winding scheme. With coupling incorporated the required value of self-inductances of the input and output inductors for the same performance is reduced. Also, they can be wound on the same core, thereby resulting in a reduction in size. The conventional method of tuning the coupling coefficient by adjusting the air-gap is tedious. A split winding scheme for the distribution of windings over three limbs of E-core for obtaining the desired coupling coefficient is presented. The split winding scheme for the design of coupled inductors for bridgeless SEPIC converter rated for 500 W, 20 kHz is illustrated. The effect of coupling on the volume, weight, cost, and efficiency of the converter is compared with the conventional SEPIC converter without coupling for a similar performance. The performance of the proposed converter is evaluated using MATLAB/Simulink simulation and experimental results with a laboratory prototype rated for 500 W.

Detection of Winding Faults Using Image Features and Binary Tree Support Vector Machine for Autotransformer

Autotransformer (AT) is the most core power supply equipment, and overvoltage and short circuit (SC) fault may lead to winding deformation, which will have a negative impact on its insulation and even affect the operation of a train. The frequency response analysis (FRA) is widely used for detecting winding faults in a transformer. However, the direct measure of FRA for each split winding fails because the split windings are adopted to satisfy the impedance requirement of a high-speed railway, where the windings are connected inside the tank. A novel fault interpretation method based on image features and binary tree support vector machine (SVM) is proposed, which can get the condition of three windings in one measurement. Winding faults caused by different windings are simulated, including SC defect, axial deformation, and series capacitance variation, and the FRA curves are measured under various faults. Then, the features of the gray-level gradient co-occurrence matrix and the gray-level difference statistics are got from the polar plot of FRA. Finally, the image features are used as the inputs to the binary tree SVM for fault type and faulty winding classification. The results show that the proposed method has high accuracy for identifying fault type and faulty winding in AT.

Split-Capacitor Dual-Active-Bridge Converter

In this article, a split-capacitor (SC) dual-active-bridge (DAB) converter is proposed. In the proposed converter, dc-link capacitors in both the input and output are split, and primary and secondary windings of the transformer are connected to midpoints of the input and output dc links, respectively. Although the switch current stress of the proposed converter is twice that of conventional DAB converter, its switch voltage stress is reduced to half. Therefore, the proposed converter has higher conduction loss than the conventional DAB converter, however, the switching loss can be reduced, which implies that the proposed converter is beneficial and can achieve higher efficiency than the conventional DAB converter as switching frequency increases. In addition, owing to the SC structure, no dc-blocking capacitors are required and the proposed converter can be readily connected to neutral-point-clamped or half-bridge-type converters without increasing the number of dc-link capacitors. To verify the performances of the proposed converter, 3-kW prototypes are built, tested, and compared.

High-Frequency Transformer Design for Modular Power Conversion From Medium-Voltage AC to 400 VDC

This paper presents a high-frequency modular medium-voltage AC (4160 VAC or 13.8 kVAC) to low-voltage DC (400 VDC) system that is scalable in order to be used for different scale microgrids. A 15 kW, 500 kHz DC/DC converter is demonstrated as the most important stage of the system overall, which can be scalable to a 225 kW 4160 VAC to 400 VDC system. Motivation of a CLLC resonant converter and its design parameters determination is carefully illustrated. The high-frequency transformer is the key element for the DC/DC converter. Then, the paper focuses on high-frequency transformer design to realize high-voltage insulation, high efficiency, and high density at the same time. Based on a split winding UU core transformer structure, transformer insulation materials and dimension parameters are determined referring to the IEEE insulation standard. The transformer magnetic loss model is reviewed based on which loss design tradeoff is carefully analyzed. Different working frequency impact on transformer design over three different core materials is also presented. Finally, a 500 kHz transformer prototype has been developed and demonstrated with the IEEE standard required insulation tests. A whole CLLC resonant converter is also present with experiments results. The converter holds outstanding 98% efficiency and 2.9 kW/L power density.

Frequency Response Features of Axial Displacement Winding Faults in Autotransformers With Split Windings

Frequency response analysis (FRA) is an effective approach for detecting mechanical damage in the windings of a transformer. However, the application of FRA to estimate the winding condition of autotransformers (ATs) employed in the China High-Speed Railway is problematic. Because the split windings of the ATs are connected inside the tank, it is impossible to measure the FRA curves for each split winding outside the tank directly. Therefore, it is difficult to identify fault winding and effectively diagnose the overall condition of the windings. This paper explores the features of FRA curves under different fault conditions to help distinguish the fault winding. An equivalent circuit model is built for the AT with split windings, and the electrical parameters of the windings are determined using the finite-element method. The model is then employed to simulate typical axial displacement faults. The results show that the first antiresonance and resonance of the frequency response for connections involving series windings or series and common windings may be visible features for diagnosing winding faults and the fault level. Specifically, the first and second resonances of the frequency response for the common winding connection may be regarded as the primary feature for identifying fault windings.

TCSR Features Ensuring the Prevention of Voltage Resonance During Power Transmission Line Single Phase Auto-Reclosing

A description is provided of the operating mode of a line equipped with a thyristor-controlled shunt reactor (TCSR) with split valve-side windings, in a single-phase ARC (SPAR) cycle after arc quenching. It is shown that a TCSR is sufficiently fast to prevent the development of resonant overvoltages in the open-phase operating mode of a power transmission line (PTL).

Use of TCSR with Split Windings for Shortening the Spar Cycle Time in 500 kV Lines

The arc-fault recharge phenomenon in single-phase automatic reclosure (SPAR) of a line is examined. Abrief description is given of the design of a 500 kV thyristor controlled shunt reactor (TCSR) with split valve-side windings. This type of TCSR is shown to effectively quench a single-phase arc fault in a power transmission line and shortens the SPAR cycle time.

Winding temperature prediction in split-winding traction transformer

Incombustible features of resin make multiwinding dry-type transformers suitable for use in traction systems. Nevertheless, due to resin's heat transfer property and the special structure of traction transformers, temperature distribution in traction transformers is undesirable and it is essential to study its thermal behavior. In this research paper, the thermal behavior of traction transformers is modeled using thenite difference approach. After validating the model results (using the experimental results), the temperature distribution in a cast-resin traction transformer with split windings is calculated. The thermal behavior of the split-winding traction transformer is compared to the normal two-winding cast-resin transformer. A traction transformer usually feeds electronic converters; the converter system as a nonlinear load causes harmonics to appear in the winding currents. Thus, the thermal behavior of a traction transformer has been modeled in the presence of harmonic currents and their effects on temperature distribution have been discussed.

10 kW Contactless Power Transfer System for Rapid Charger of Electric Vehicle

A contactless power transfer system for charging electric vehicles requires a high efficiency, a large air gap, and a good tolerance to lateral misalignment and needs to be compact and lightweight. A double-sided winding 10 kW transformer based on a 1.5 kW H-shaped core transformer was developed for a rapid charger. Even though the transformer capacity was increased, the dimensions of the 10 kW transformer were almost the same as those of the 1.5 kW transformer. In this paper, the design concept for this 10 kW transformer and the results of experimental are described. The transformer was found to exhibit more than 94% efficiency with a mechanical gap of 70mm. Even for gap change and position change, an efficiency of over 92% was maintained. In a contactless power transfer system with a series resonant capacitor, the primary terminal voltage increases with increasing power. This overvoltage may lead to the problem of breakdown voltage of capacitor and the breakdown of winding insulation. To prevent such an overvoltage occurring, it is suggested that the primary winding and the series capacitor are split into two pieces or more respectively, and the split windings and capacitors are alternately connected in a series. Electric vehicles using a contactless power transformer for rapid charging would also uses normal charging. Therefore, the 10 kW transformer was designed to be compatible with the 1.5 kW transformer. Consequently, electric vehicles equipped with the 10 kW transformer can charge even using a 1.5 kW ground transformer, without decrease efficiency.

Winding Loss Simulation and Optimal Design of a High Frequency Coaxial Transformer

A high frequency coaxial transformer (HFCT) with a split winding structure and litz wire has been developed for high frequency (HF) and high power DC/DC converter applications. A method combined numerical analysis of magnetic field and analytical calculation of litz wire winding losses, taking into account conduction losses and proximity effect losses, is proposed for the designed HFCT. The experimental results validate the winding loss calculation method. The measured results demonstrate that the voltage ratio has a good agreement with the turn ratio over the frequency range from 0.1MHz to 1MHz, indicating that the high coupling efficiency has been obtained.

An Improved Control System for a Split Winding Bearingless Induction Motor

Different types of bearingless induction motors have been reported in the literature. One of them is the rotor cage induction motor with split windings. Continuing research about this theme, this paper proposes a new control system. Since the radial forces are consequences of magnetic energy changes, the modeling and the speed control of this system are implemented in the reference frame of the airgap magnetic flux. In addition, due to the lag between the stator current vector and the reference flux, an automatic correction of the angular orientation of the Cartesian coordinates of the position sensors is proposed. In a wide operation range, experimental results show the effectiveness of this approach.