Winding Turns Research Articles

Analysis of Rectangular Cross-Section Toroidal Helix Geometry for Winding Length Optimization

Recent advances in additive direct-write circuit technology have enabled the fabrication of inductive winding geometries previously considered impossible by conventional methods. In this letter, a winding fabricated around a rectangular cross-section toroidal core is considered. As an extension of research embedding toroidal cores within printed circuit board, this letter considers the minimization of the winding length when the vertical path, along the toroidal z-direction, is not restricted to be perfectly vertical, which is only possible with direct-write techniques. It will be shown that the exact analysis results in a transcendental equation for the optimized vertical midpoints of the winding turns. However, a few reasonable approximations allow an analytical expression for this optimized midpoint to be found. Comparisons of this approximate analytical solution to the exact solution found by numerical methods will be presented for typical toroid dimensions. The accuracy of this approximate solution with changing turn density will also be presented. For typical toroid dimensions, it was found that the choice of midpoint can change the total winding length by as much as 10%. The analytical approximate solution for the midpoint was found to deviate by 2.75% of angular gap from the exact solution, which resulted in an error in the minimum winding length of only 0.07%, a result which will be discussed in this letter.

Уравнения магнитоэлектрического вентильного двигателя при витковых замыканиях обмотки статора

The article considers the differential equations of a switched permanent magnet motor in which a short-circuit fault occurred in one or more turns in one of parallel stator winding branches. Owing to the occurred asymmetry of the phase quantities, symmetrical line-to-line voltages at the stator winding terminals are assumed. It is shown that turn-to-turn short-circuit faults give rise to non-sinusoidal and imbalanced phase currents and voltages at the nominal load torque on the shaft, and it should be noted that initially, a growth of the frequency and ratios of currents in the phases with an increase in the number of short-circuited turns are observed, after which the phase currents tend to decrease (with a continuing growth in the current through the short-circuited loop), and the rotor stalling occurs. The growth of motor rotation frequency and decrease of its overloading capacity take place due to a growth in the demagnetizing effect of armature reaction caused by the current through the short-circuited stator winding turns.

Airgap Flux-based Detection and Classification of Damper Bar and Field Winding Faults in Salient Pole Synchronous Motors

Recent cases of broken damper bars and shorted field winding turns in synchronous motors (SMs) have shown that rotor faults can degrade motor performance and lead to a forced outage of the motor and driven process. However, detection of SM rotor faults has not received much attention since SMs are not as common as induction motors. Detection of SM rotor faults is difficult, as the damper bar is active only under the starting or load transients, and shorted field winding turns result only in a slight increase in rotating asymmetry. SM rotor fault testing in the field mainly relies on visual inspection or off-line tests, and new test methods that can provide reliable detection of the faults without motor disassembly is highly desirable. In this article, new test methods for not only detecting, but also classifying the two types of SM rotor faults under motor standstill and starting are proposed. A finite element and experimental study on 1.1 MW and 30 kW salient pole SMs are provided to verify the proposed methods. It is shown that damper and field winding faults can be detected and classified with high sensitivity and reliability compared to conventional tests.

Simulation of Transient Processes in a Generator-Transformer-Load System with Non-Symmetry of Phase Windings of the Stator and Saturation of the Magnetic System

Transient processes of a generator-transformer-load system are considered taking into account the saturation of its magnetic system. A method is proposed for numerical simulation of the transient processes of a synchronous machine with the possibility of taking into account the asymmetry of the stator winding and the saturation of the magnetic system. The appearance of asymmetry is possible if the synchronous machine is damaged, in particular, during inter-turn short circuits in the stator winding. It is based on the direct solution of the differential equations of equilibrium of the emf and voltage drops in the windings in phase coordinates together with the equation of motion of the rotor. In this case, the contour of each phase winding of the stator is described by a separate equation, and different phase parameters can be taken into account. The mathematical model of the system is realized in the software package MATLAB. The model takes into account one of the possible types of nonsymmetry – an unequal number of turns in phase windings, which makes it possible to simulate interturn short circuits without taking into account the appearance of additional short-circuited circuits. The model was verified by comparing the transient calculation results obtained using the developed model and using the MATLAB Simulink tools. The simulation results for the idle and load modes are analyzed. The obtained results allowed to draw a conclusion about the adequacy of the realized model

Design of the Number of Transformer Shielding Winding Turns for Minimizing Low-Frequency Common-Mode Noise in Flyback Converters

Transformer shielding techniques are widely applied to suppress common-mode (CM) noise. As an important shielding method, winding shielding gains lots of attention because of its convenience and cost effectiveness. For suppressing CM noise effectively, the number of shielding winding turns should be carefully decided. This paper proposes a design method of the number of transformer shielding winding turns for minimizing low-frequency CM noise in flyback converters. This is realized through exploring the relation between low-frequency CM current and the number of shielding winding turns. With this method, the optimal number of shielding winding turns can be obtained without calculation and comparison of CM currents in converters with different shielding winding turns. By comparing CM noise measurement results, the proposed method is validated. The proposed method can be a guideline on the design of transformer shielding winding.

Multilayer Flexible Printed Circuitry Planar Transformer With Integrated Series Capacitance for an LLC Converter

The LLC resonant converter is popular but needs a discrete series resonant inductor and a capacitor. In order to cut down component count, a novel multilayer flexible printed circuitry (FPC) planar transformer with integrated series capacitance and inductance is proposed in this paper. This planar transformer consists of two sets of multilayer open-ended windings coupled with each other to produce the integrated resonant capacitor. The equivalent resonant capacitance can be controlled by the number of the layers without changing the number of primary winding turns or pattern. The proposed transformer successfully integrates the resonant capacitor and the resonant inductor, into a single component. A model is established to accurately predict the equivalent series resonant capacitance of the transformer from the physical structure. Several multilayer FPC planar transformers are built to test the model. Practical measurements and theoretical results show good agreement and validate the proposed model. Finally, an LLC power converter with 94% efficiency is built to demonstrate the proper functioning of the proposed multilayer FPC planar transformer.

Comprehensive Monitoring of Field Winding Short Circuits for Salient Pole Synchronous Motors

An interturn insulation failure in the field winding of synchronous motors is a common problem that can lead to degradation in performance and accelerated wear of motor components. Existing offline tests for detecting this fault are known to be unreliable and inconvenient to perform, as they require motor disassembly. Online monitoring based on airgap flux monitoring has been proven to be successful, but could lack sensitivity for cases where the number of turns per pole is large. In addition, field winding turn shorts can be intermittent depending on the centrifugal force and could be unobservable at standstill or under an steady state operation. Therefore, monitoring of the turn faults under standstill and starting conditions with high sensitivity and without motor disassembly is desirable. In this paper, the detection of field winding short circuits for salient pole synchronous motors based on an airgap search coil under the starting transient, and new methods for standstill testing without motor disassembly are proposed. Two-dimensional finite element analysis and experimental testing on a 30-kW motor are given to verify the claims made. It is shown that the proposed set of tests can provide sensitive and reliable detection of field winding short circuits under standstill and starting conditions.

Modified Series and Tapped Switched-Coupled-Inductors Quasi-Z-Source Networks

This paper proposes two coupled-inductors-based Z-source networks, called the modified series and tapped switched-coupled-inductors quasi-Z-source networks (mSSCL-qZSN and mTSCL-qZSN, respectively). These networks offer high voltage gains with less-than-unity winding turn ratios (n <; 1), resulting in a reduced inductive element size. Other advantages include a less number of active components and their lower ratings and a higher efficiency. In addition, a lower magnetic core size is required for the proposed ZSNs due to the lower peak magnetizing current. The performance principles and detailed comparative analysis are provided and confirmed through experiments on a 200-W dc-dc converter.

The Influence of Stator Winding Turns on the Steady-State Performances of Line-Start Permanent Magnet Synchronous Motors

The variation of stator winding turns will directly affect the key parameters of a motor, such as winding resistance and winding reactance, which further affect the steady-state performance of the motor. In order to get excellent steady-state performance from line-start permanent magnet synchronous motors (LSPMSMs) under different load powers, taking an 11 kW LSPMSM as an example, the finite element method (FEM), combined with the steady-state phasor diagram and torque angle characteristic, are used in this paper for the optimal design of the stator winding turns of the prototype. The correctness of the model is verified by comparing the experimental data with the calculated data. First, the influences of different stator winding turns on the no-load, back-induced electromotive force (EMF), as well as on inductance and overload ability are studied, and the variation mechanism is obtained. In addition, from the perspective of the torque angle characteristic, the influence of the change in synchronous inductance caused by the number of turns on the steady-state power angle is studied. Second, the variation of the current and power factors with turn number is obtained by studying the steady-state power angle and end voltage. Based on the coupling relationship between the no-load back EMF and the power angle, the mechanism of non-linear variation of current and power factor is revealed. Finally, the variation of the number of turns on the core loss and eddy current loss is analyzed under various operating conditions, and the variation mechanism is revealed, based on the armature reaction theory.

Design and Simulation of a Brushless Self-Excited Air-Core Compensated Pulsed Alternator

A novel brushless self-excited air-core compensated pulsed alternator (BSACPA) is presented in this paper. It consists of two submachines in cascade, among which one serves as an exciter and the other works as a generator. The rotor windings of the two submachines are connected by a reverse phase sequence to realize reversal of the magnetic field. The stator windings are connected by a rectifier to realize the brushless self-excited structure. As an air-core compensated pulsed alternator (CPA) of new topology, it is necessary to derive its mathematical model and carry out a comparative design. Thus, this paper focuses on the detailed design and analysis of a BSACPA prototype, which includes dimensional design and equivalent circuit establishment. In addition, the critical speed is also acquired. Accordingly, the numbers of winding coil turns are designed to increase the discharge current and power based on the theoretical analysis. Finally, the analysis and design are verified by finite-element analysis (FEA).

Detection and classification of turn fault and high‐resistance connection fault in inverter‐fed permanent magnet machines based on high‐frequency signals

Winding turn fault and high-resistance connection (HRC) fault will lead to different consequences and require different mitigation actions. In this study, the differentiating features between a turn fault and HRC fault are analysed and compared in a three-phase surface-mounted permanent magnet machine fed by the inverter with pulse-width-modulation voltages. The resultant high-frequency components in both voltages and currents are utilised for the fault detection and classification based on the high-frequency impedance and ripple current, without requiring modifications to the machine or interface design. Extensive simulations show that this method is capable of fault detection and classification in both transient and steady-state operations.

Simulation of Fast-Rise Transients in a Large-Power Transformer Winding

A high-altitude electromagnetic pulse (HEMP) may pose a significant threat to the electrical power grid. In this context, the present study considers the potential impact of the HEMP early-time component (E1) on the winding of a typical transmission power line transformer. A time-domain, fully electromagnetic, three-dimensional, finite-element model was used to simulate the propagation of an E1-induced voltage surge into the transformer winding. The analysis is focused on the first few turns of the winding, the ones that are impacted by the largest electric field resulting from the applied pulse. The model follows the transient dynamics, while the pulse is traveling along the conductor, and the electric field is established across the insulation gaps through capacitive coupling. The simulations also considered the effect of an electrically floating, “shield” winding conductor. This is used as a countermeasure to improve the voltage uniformity across the winding during fast-rise transients. In this case, the propagation of the E1-induced pulse is compared with that from a slower rising, lightning standard waveform. The simulation results show that the presence of the shield conductor can effectively reduce the peak electric field between winding turns, in the presence of either E1 or lightning waveforms.

A New Improved Trans Z Source Inverter based Three Phase UPS

Objective: In applications like Wind Energy Conversion System, electric cell power conversion and Grid-connected PV generation, a small DC source voltage should be boosted to induce fascinating AC output voltage. Methods/Statistical Analysis: Z Structured Impedance Source Inverter (ZSI) is well-liked for its buck to boost operations. The high voltage gain will be obtained from the normal Z Structured Impedance Source Inverter at low modulation index state. On the other side, a little modulation index state produces high voltage stress at the inverter side switches. To defeat this problem, a Trans Z Structured Impedance Source Inverter (TZSI) is developed. In TZSI, transformer winding turns demand is high and the windings get burnt because of high instant current throughout shoot through length. Findings: A new topology of Trans Z Structured Impedance Source Inverter is introduced in this paper to boost the voltage gain fair enough. In this new topology the winding turn’s usage is smaller amount and consequently inverter gain is lift up by lower the modulation index. To validate the ideas planned in theories, experimental results were taken and bestowed in this paper. Application: This inverter is utilized for three faze Uninterruptable Power Supply. The proposed inverter is designed and simulated in MATLAB/Simulink podium for 3 KVA load capacity and it will sustain the specified output voltage with the substantial drop in voltage at battery bank side. Keywords: PWM Inverter, Shoot Through Period, Trans Z Source Inverter (TZSI), Uninterruptable Power Supply (UPS), Z Source Inverter (ZSI)

COMPARATIVE ANALYSIS OF THE ACCURACY OF COMMUTATION CURRENT MODELS, WHICH TAKE INTO ACCOUNT THE PRESENCE OF SHORT-CIRCUITED TURNS OF THE ARMATURE WINDING

A modern strategy for locomotive maintenance is based on the operational diagnostics of their equipment. Currently, a large number of locomotives are equipped with DC electric motors. These locomotives will be operated in the short term. About half of the failures of DC electric motors are caused by the failure of the armature structure elements and, above all, the armature winding. Detection of the nature of damage to this winding and the extent of its damage reduces the time spent on repairing the motor. The large fleet of locomotives with DC commutator motors determines the relevance of the problem of diagnosing the armature winding. The greatest amount of information about the state of the winding contains the dependence of the commutation current of its sections on time. Existing publications have paid great attention to the development of competing or complementary models of such dependencies. However, solving the problem of quantitative comparison of the developed models still requires significant efforts. The object of the paper study is the error of modeling of commutation current, provided that some of the armature winding turns are short-circuited. The aim of the study is a comparative analysis of the existing models of this current. In order to achieve this goal, the tasks were solved, as follows: 1) to clearly distinguish between models, according to methods for determining the dependence of current on time; 2) to determine the degree of physical and mathematical correctness of each of these models; 3) to assess the conditions of existence and numerical values of the differences between these models. Comparison of models in terms of accuracy has shown that the best is the selection of a separate current model for each specific combination of two special parameters. These parameters describe the degree of shorting of the armature winding section. However, it is inconvenient that with different combinations of parameters, one has to operate with different mathematical expressions. The generalized model of commutation current gives the same expressions for all combinations of the specified parameters. However, this model should be enhanced to improve its accuracy in the field of large numerical values of parameters.

Transformer Turn-to-Turn Fault Protection Based on Fault-Related Incremental Currents

Winding turn-to-turn fault (TTF) is one of the most reported reasons for transformer unplanned outage. If its occurrence is not detected at an early stage, it can develop into a costly phase-to-ground fault. In this paper, a novel algorithm based on the fault-related incremental currents is proposed to detect a low-level transformer TTF. This paper shows that the performance of the proposed method is independent of the transformer operating condition. Therefore, it is reliable even under the presence of power system transients such as the external faults. In addition, the proposed algorithm can be configured uniquely and easily. This feature prevents the algorithm from unnecessary trips. These trips can be considered as the general problem that most of the past presented methods face. The experimental tests used for verification of the algorithm show that, regardless of the transformer winding configuration and its pre-fault operating conditions, the proposed algorithm can accurately detect the TTF, which involves only 1% of the winding turns, in less than one cycle of power frequency. The reliable and secure performance of the proposed algorithm shows that it can be widely used in the advanced numerical relays.

A simple screening current-induced magnetic field estimation method for REBCO pancake coils

The development of NMR/MRI REBa2Cu3Oy (REBCO, RE = rare earth) magnets is happening all over the world. It has been found that screening current-induced magnetic fields (SCMFs) are a serious problem for NMR/MRI magnets wound with REBCO tapes. The reduction of SCMFs is strongly desired, and the estimation of SCMFs is also desired at the design stage of REBCO magnets. In order to evaluate a SCMF, a finite element method (FEM) or a boundary integration method is needed thus far, and a high-level simulation technique is required. In this paper, we develop an easy method to estimate a SCMF without a high-level simulation technique. In this method, the inductance of a winding turn is calculated and then a screening current is estimated according to the magnetic field penetrating into the winding turn. The SCMF is obtained from the estimated screening current. The SCMFs computed by the proposed method were compared with measurements and simulation results of the FEM. The results agreed well, but we can see a large difference. However, the SCMFs found by the proposed method are accurate enough to know they are at the design stage without the use of a high-level simulation technique.

High Step-Up Y-Source Coupled-Inductor Impedance Network Boost DC–DC Converters With Common Ground and Continuous Input Current

High step-up Y-source coupled-inductor impedance network boost dc–dc converter with common ground and continuous input current is presented in this paper. The proposed converter has added auxiliary diodes and capacitors to three-winding Y-shaped coupled-inductor cells to constitute the current conduction path and realize the voltage-double function. Compared to other magnetically coupled boost converters, the proposed converter can produce the higher voltage gain with more degrees of freedom in winding match. The same output gain can be obtained by using different winding turn ratios. Also, the proposed converter has a common ground and realizes the continuous input current. The corresponding topologies and steady operation principles are analyzed. The experimental results in a 300-W prototype have verified the validity of the theoretical analysis.

Design investigation of electromechanical generator for energy harvesting

In this paper designs of electromechanical generator for low frequency energy harvesting have been investigated. Simulation with finite element method has been conducted in order to determine highest output voltage of simple and robust generator consisting of permanent magnet and windings. In first part round magnets have been used in spherical and cylindrical form, benefiting from their ability to roll through winding with almost no mechanical friction inducing voltage in into windings. In the second part spindles with smaller radius than circumference of magnet were added to axis to increase rotational velocity of magnet in ambition to further increase induced voltage. As a result of added spindles and use of different magnet shapes length of winding turn varied and resistance of winding varied with it. To ensure similar conditions, windings have been recalculated to lowest electrical resistance using same fill factor, resulting in less winding turns decreasing induced voltage. In case of same kinetic energy input, higher rotational velocity combined with lower inertia produced higher induced voltage output.

A Magnetic Integration Half-Turn Planar Transformer and its Analysis for LLC Resonant DC-DC Converters

A high frequency planar transformer with integrated leakage inductance and half-turn secondary windings is proposed for LLC isolated DC-DC converters. The primary windings are wound on both the center leg and the sides leg of an EI planar ferrite core to integrate the leakage inductance. With the proposed method, the magnetizing inductance is constant while adjusting the leakage inductance, thus the design of the magnetizing inductance and the leakage inductance can be decoupled. To adapt the high voltage transform ratio from 380V to 12V, the number of turns of the secondary windings is designed to be 0.5. The output voltage ripple of the LLC converter equipped with the proposed transformer is analyzed and its output filter is designed. The characteristics of the proposed transformer are simulated by ANSYS Maxwell and Simplorer. Finally, a 360V ~ 400V input, regulated 12V output, 750W LLC resonant converter with silicon carbide (SiC) devices was built with the proposed transformer. The evaluated converter realized a power density of 23.1W/cm 3 and a peak efficiency of 97% with all the auxiliary power and control circuit included.

Winding Switching and Turn Switching in Permanent Magnet Vernier Machines for Wide Speed Range Operation and High Efficiency

This paper proposes to turn to switch along with winding switching for high-efficiency of permanent magnet vernier machines (PMVM) during wide speed range operation for electric vehicles application. For winding switching, the three-phase winding of the machine is divided into two sets of windings, namely, winding set A, B, C and winding set X, Y, Z. For turn switching, the number of turns for one set of winding is changed. With the different number of turns for winding set X, Y, Z, the efficiency of the machine can be significantly improved. Initially, the basic electromagnetic characteristics, such as the flux linkage, back electromotive force (EMF), torque, and phase voltages of the machine are investigated using winding switching and turn switching. Then, the output power, torque-speed curve, core losses, efficiency, and power factor of the machine are analyzed in detail using a different number of turns. In addition, the transient effects of winding switching and turn switching have been analyzed. Finally, a control strategy is proposed which combines turn switching and winding switching to ensure high-efficiency of PMVMs during wide speed range operation. A PMVM is designed and driven in accordance with the proposed control strategy (PCS) to show the characteristics of PCS. The PMVM driven with PCS is compared to a recently presented PMVM. The recently presented PMVM is driven by a different control strategy and is analyzed with two different kinds of steel laminations that are general steel (50TW470) and special steel (20JHF1300).