Compensation Winding Research Articles

Magnetic field normalization in residential premises located above built-in transformer substations 6(10)/0,4 kV power 100-400 kVA

The purpose of the work is to define methods and means of screening, sufficient to reduce to a safe level the low frequency magnetic field in residential premises of old buildings, located above built-in transformer substations 6(10)/0,4 kV power 100–400 kVA at short distances to the premises. To achieve this goal, a modified method for synthesizing active shielding systems of the magnetic field for transformer substations at short distances from the substation to the floor of the premises, and its experimental verification was carried out on a full-scale physical model of a transformer substation power 100 kVA with a physical layout of the synthesized active shielding system. A synthesis of active shielding systems of magnetic field for transformer substations with a power of 100–400 kVA at short distances from the substation to the floor of the premises and an analysis of their effectiveness were carried out. It was determined that the normalization of the magnetic field on the floor surface for transformer substations with a power of 100 kVA using a synthesized active shielding system with one compensation winding is possible at distances of at least 1,15 m from the substation, and with two windings - at least 1,02 m. It was determined that normalization of the magnetic field on the floor surface for 400 kVA transformer substations using a synthesized active shielding system with two windings is possible only at a distance from the substation of at least 1,6 m. An analysis of the effectiveness of the combined use of active and passive shielding was conducted. It was determined that the combined use of synthesized two-channel active shielding systems and a passive flat electromagnetic shield made of 4 mm thick aluminum sheet allows reducing the magnetic field above the built-in transformer substation with a power of 100 to 400 kVA to the normative level while limiting the distance from the substation to the floor of the premises to at least 1,08 m and provides protection of public health from the effects of the low frequency magnetic field.

Hybrid Active and Passive Cable Contour Shielding of Magnetic Fields of Double-Circuit Overhead Power Lines

The purpose of the work is to design a hybrid screen designed to reduce the level of the magnetic field generated by double-circuit overhead power lines, to increase the efficiency of shielding the original magnetic field in residential buildings, to the level of sanitary standards and to reduce the sensitivity of the system to changes in system parameters. To achieve this goal, the structure of a hybrid screen was determined, consisting of a double contour active and a cable contour passive part. The developed hybrid screen is characterized by increased efficiency in reducing the magnetic field of industrial frequency. Designing a hybrid screen comes down to solving a minimax vector optimization problem, in which the vector objective function is calculated based on solution to Maxwell's equations in a quasi-stationary approximation using the COMSOL Multiphysics software package. The solution to the minimax vector optimization problem is calculated based on multi-particle swarm optimization algorithms from Pareto-optimal solutions taking into account binary preference relations. During the design of the hybrid screen, the coordinates of the spatial location of the two compensation windings, as well as the magnitude of the currents and its phases in the windings of the active screen, were calculated. The important results are theoretical and experimental studies on the effectiveness of the designed hybrid magnetic field shield generated by double-circuit overhead power lines. The significance of the results obtained lies in the fact that practical recommendations are given for a reasonable choice of the spatial arrangement of two shielding windings of a robust system of hybrid shielding of the magnetic field generated by double-circuit overhead power lines.

Design and Performance Research of a Novel Iron-Core Permanent Magnet Compensated Pulsed Alternator With Segmental Squirrel-Cage

Compensated pulsed alternator (CPA) can realize transient high current discharge by compressing magnetic field through compensating element, which has important application in pulse power field. The compen- sation shield and short circuit compensation winding are usually used as compensation elements, but the local compensation effect will be affected by the opposite eddy currents or conductor currents under other poles at maximum discharge time. To solve this problem, a novel iron-core permanent magnet CPA (PMCPA) with segmental squirrel-cage is proposed in this paper. At the time of maximum discharge, the bars' current of each segmental squirrel-cage segment will not be affected the bars' currents in opposite direction of other segments, which has better local compensation effect. In addition, the permanent magnet (PM) excitation eliminates the brush and slip ring and improves the reliability of operation. First, the design basis and scheme of the PMCPA are introduced. Second, the dynamic mathematical model of the PMCPA is presented. Third, the finite-element model of the PMCPA is established to analyse. Fourth, the prototype is manufact- ured to test and validate. Through analysis and verification, the superiority of segmental squirrel-cage compensation is proved, which provides a new idea for the optimization and development of compensation elements.

Research on Step-down Resonance Suppression and Filtering Device

In recent years, offshore wind farms have developed rapidly, and their installed capacity is getting bigger and bigger, and the offshore distance is getting farther and farther. In order to meet the needs of large-capacity and long-distance offshore wind power transmission, the AC submarine cable has the characteristics of long distance, high voltage and large cross-section. Along with the significantly improved transmission capacity, its equivalent capacitance is also increasing, which further reduces the resonance frequency of the offshore wind power AC transmission system. If the parallel resonance frequency of the offshore wind power transmission system is close to the main harmonic current frequency band of wind turbines, it will cause harmful system resonance and harmonic amplification, significantly increasing the harmonic current of grid-connected lines and the voltage distortion rate of nodes in nearby power grids, and seriously affect the safety of equipment and the safe and stable operation of offshore wind power transmission system. A step-down resonance suppression filtering device applied to the offshore wind power transmission system is proposed. The AC cable is connected to the low-voltage 35 kV side of the compensation winding of the centralized control center to eliminate the resonance risk of the 220 kV system and filter out the harmonic current. Compared with the existing technical scheme, the device has the advantages of simple control, reliable operation, stable resonance suppression effect, low operation loss and the like, and has great engineering popularization value.

The method of multi-objective parametric design of magnetic field active canceling robust system for residential multy-story buildings closed to double-circuit overhead power lines

Aim. Development the method of multi-objective parametric design for robust system of active canceling of magnetic field based on binary preference relations of local objective for multi-objective minimax optimization problem. Methodology. Spatial location coordinates of the compensating winding and the current in the shielding winding were determined during the preference-based multi-objective parametric design of systems of active canceling based on solution of the vector minimax optimization, in whith the vector objective function calculated based on Biot-Savart's law. The solution of this vector minimax optimization problem calculated based on nonlinear Archimedes algorithm. Components of Jacobi matrix and Hesse matrix calculated based on multi-swarm multi-agent optimization. Results. Theoretically and experimentally confirmed the effectiveness of reducing the level of the magnetic field in residential multy-storey old building of a double-circuit overhead power transmission lines with a barrel-type arrangement of wires by means of active shielding with two compensation winding. Originality. The method of multi-objective parametric design for robust system of active canceling of magnetic field based on binary preference relations of local objective for multi-objective minimax optimization problem is developed. Practical value. It is shown the possibility to reduce the level of magnetic field in residential multy-storey old building closed to double-circuit overhead power transmission lines with a barrel-type arrangement of wires by means of system of active canceling with two canceling winding to a level safe for the population with an induction of 0.5 μT.

Modeling Dependence of Active Power Loss in Plunger Core Arc Suppression Coils on Applied Voltage and Compensation Winding Current

Modeling Dependence of Active Power Loss in Plunger Core Arc Suppression Coils on Applied Voltage and Compensation Winding Current

Synthesis of an effective system of active shielding of the magnetic field of a power transmission line with a horizontal arrangement of wires using a single compensation winding

Aim. The theoretical and experimental studies of the effectiveness of reducing the level of the magnetic field in two-storey cottage of the old building of a power transmission line with a horizontal arrangement of wires by means of active shielding with single compensation winding. Methodology Spatial location coordinates of the compensating winding and the current in the shielding winding were determined during the design of systems of active screening based on solution of the vector game, in whith the vector payoffs is calculated based on Biot-Savart's law. The solution of this vector game calculated based on algorithms of multi-swarm multi-agent optimization. Results The results of theoretical and experimental studies of the effectiveness of reducing the level of the magnetic field in two-storey cottage of the old building of a power transmission line with a horizontal arrangement of wires by means of active shielding with single compensation winding are presented. Originality. For the first time, the theoretical and experimental studies of the effectiveness of reducing the level of the magnetic field in two-storey cottage of the old building of a power transmission line with a horizontal arrangement of wires by means of active shielding with single compensation winding are considered. Practical value. From the point of view of the practical implementation it is shown the possibility to reduce the level of magnetic field in two-storey cottage of the old building from power transmission line with a horizontal arrangement of wires by means of active shielding with single compensation winding to the sanitary standards of Ukraine.

USE OF T-SHAPED TOOTH IN A DIRECT CURRENT MACHINE WITH A WINDLESS ROTOR

The electric direct current machine with a windingless rotor (DCWR) is significantly different from the classic direct current machine; its magnetic system does not have a common yoke and consists of a number of magnetically loose teeth and grooves open on both sides. The presence of grooves in which there is no bottom creates a number of air gaps, which leads to a decrease in the magnetic conductivity of the magnetic conductor in the transverse direction, which, again, leads to a weakening of the reaction field of the Фa armature and the rejection of additional poles and compensation winding. Therefore, the size of the working air gap can be reduced to the minimum possible value from a technological point of view. According to the structural schemes, the DCWR belongs to the type of induction machines with two stationary windings on the stator and a toothed magnetic conductor of the rotor, in which the magnetic induction in the working air gap changes only in magnitude without changing the sign. Therefore, the rotor in the DCWR is not remagnetized and is made of ordinary structural steel. The inductor type of the magnetic system allows having only one, common for all poles, excitation winding in the DCWR, and the rotor is very similar to the rotor of multi-pole synchronous machines with permanent incorporated magnets. At the same time, DCWR does not have permanent magnets, which allows to significantly reduce the cost of an electric machine. Replacing straight teeth with T-shaped ones allows you to significantly increase the efficiency of the DCWR design by improving its heat dissipation. The results of calculations and modeling of the stationary thermal field presented in the article show that the use of T-shaped teeth allows you to significantly increase the overload capacity of the DCWR or increase its power.

Study on the effect of different pre-excitation factors on the output characteristics of MCSR

This paper takes the BKFSZT-30000/400 three-phase eight-limb magnetically controlled shunt reactor as the research object. Firstly, an electromagnetic transient simulation model is established based on the parity principle to verify the operating characteristics of the MCSR during direct energization and pre-excitation energization. On this basis, the influence of the pre-excitation capacity and the target capacity on the output characteristics of the MCSR is investigated. The results show that during the pre-excitation process the currents of working and control winding produce a DC component and a harmonic component dominated by the second harmonic, with the size of both DC components mainly influenced by the pre-excitation capacity and the attenuation determined by MCSR; the variation of the working harmonics is mainly influenced by the target capacity, while the size and attenuation of the control harmonics are determined by the pre-excitation capacity and the target capacity respectively. The results of the study clarify the output characteristics of the MCSR when energization with pre-excitation and provide a reference for further analysis of the interaction with the grid. Finally, to solve the problem of no reliable external power supply for pre-excitation, a fast excitation energization method with short-connected of the compensation winding is provided and verified by simulation.

Analysis of Opening Angle for Radial Magnetic Field Compensation Windings of Double-layer Ferromagnetic Cylindrical Shells

A double-layer ferromagnetic cylindrical shell causes a magnetic anomaly in its surrounding space under the action of the geomagnetic field. Aiming at the problems of poor compensation uniformity and obvious local magnetization caused by the single-branch winding compensation method, a double-branch winding solution is proposed. By establishing a double-layer ferromagnetic cylindrical shell model, the radial magnetization characteristics of the cylindrical shell under the action of the vertical geomagnetic field was analyzed, and the opening angle of double-branch winding was studied. By optimizing the opening angle of compensation windings in the three proposed configuration schemes with respect to the minimum abnormal magnetic field, the optimal ranges of opening angle for the double-branch compensation windings were determined.

Design of a direct current motor with a windingless rotor for electric vehicles

Modern electric vehicles typically exploit synchronous motors with magnetoelectric excitation as traction engines. While possessing a series of undeniable advantages, the synchronous motor has one significant drawback ‒ the high cost predetermined by the high price of permanent magnets. In addition, the impossibility to disable a magnetic field in case of engine malfunction can lead to an emergency on the road. Given this, there is a need to design new structures of electrical machines with electromagnetic excitation. The structure of a DC traction motor with electromagnetic excitation involving the rotor or stator segmentation makes it possible to considerably weaken the field of the armature transverse reaction by decreasing magnetic conductivity of the magnetic circuit in the transverse direction. Therefore, such a structure lacks commutating poles and a compensation winding. There are no permanent magnets in the structure, all windings are stationary, an electronic switch is used instead of a collector, and a windingless low-inertia rotor does not require additional measures to remove heat. That all has made it possible to significantly reduce the cost of active materials for the traction engine and improve its reliability. To test the performance of the new design, a full-size model of the engine and a working experimental prototype were fabricated. Applying a synchronous jet engine with magnetization for the BMW i3 electric car as an analog, the engine calculations were performed and its simulation was carried out. The results of the analysis show that the mass of the new engine is 35 % greater than the mass of the analog but the cost of active materials is less than that of the analog by 63 %. The results testify to the possibility of implementing a given structure industrially

Determination of inductances for pulsating current traction motor

The object of research is a pulsating current traction motor. To improve the accuracy of its mathematical model, it is necessary to use the values of the parameters that are determined in experimental studies of the electric motor. In particular, it is important to use in the model of the electric motor inductance obtained experimentally. A method is proposed for calculating the inductance of the armature winding, main poles, additional poles and compensation winding and the total inductance of the traction motor armature circuit. The calculations are based on the results of the indirect inductance measurement method, in which the electrical values of various modes of power supply of the electric motor windings are directly measured, and the inductances are determined by auxiliary calculations. The inductances of the traction motor armature circuit have a non-linear dependence on the current flowing through them. The main difference of the study is that the measurements of the electrical parameters required for calculating the inductance are carried out over the entire range of operating currents of the windings. The essence of the proposed technique is to measure the active power in the armature winding, the winding of the main and additional poles, and the compensation winding, as well as in the armature circle as a whole when they are supplied with alternating current. According to the obtained values of active power losses and phase displacement, the corresponding reactive power losses are determined, with the help of which the inductances of the motor windings are calculated. Approbation of the methodology for calculating the conduction inductance for an electric motor of a pulsating current NB-418K6 (country of origin Russia), is used on electric locomotives of the VL80T and VL80k series (country of origin Russia). A scheme for measuring electrical parameters necessary for calculating inductance is proposed. The graphical dependences of the inductance on the armature current, built on the basis of calculations, confirmed the hypothesis about the nonlinear dependence of these inductances on the armature current. For further application of the results obtained in the simulation of the operation of the traction electric motor NB-418K6, a polynomial approximation of the total inductance of the armature circuit was performed.

Research on reducing reluctance torque of permanent magnet toroidal motor

The permanent magnet toroidal motor (PMTM) is a special motor that combines a permanent magnet motor with a deceleration mechanism. Because of the special structure of the PMTM, its reluctance torque includes cogging torque and end torque. In order to reduce the reluctance torque ripple of the PMTM and improve its output stability, the cogging torque and end torque of the motor are optimized, respectively. The structure of eccentric permanent magnet teeth improves the sine of the air gap magnetic induction of the motor, thereby effectively reducing the fluctuation of the cogging torque. It is proposed to add compensation windings at both ends of the central worm stator to reduce the fluctuation of the end torque. The dynamic compensation effect and the change in air gap magnetic induction intensity with the current applied to the compensation windings are analyzed by finite element simulation. The relationship between the compensation current and the structure parameters of the motor is derived. Finally, it is verified that the output torque ripple can be effectively reduced by adding the magnetic isolation material between the compensation winding and the three-phase winding. The research results show that the reluctance torque fluctuation can be greatly reduced by using eccentric permanent magnet teeth and compensation windings. It provides an important reference basis for the optimization design of the electromagnetic structure of the PMTM.

Hybrid Passive Cancelation Method for Reducing Common-Mode Noise in Isolated Power Converters

The shielding technique is an effective method for reducing the common-mode (CM) electromagnetic interference in an isolated power converter. However, the interwinding capacitance between the shielding layer and its adjacent winding provides the path for CM noise current. This CM noise current can be suppressed by making the averaged electric potential (AEP) of the shielding layer and its adjacent winding be equal. In this article, a balancing winding is introduced to be connected with the shielding layer for adjusting the AEP of the shielding layer to be equal to that of its adjacent winding and, thus, canceling the CM noise current. Furthermore, the hybrid passive cancelation (HPC) method is proposed in which the balancing winding is reused as the compensation winding to generate the compensation voltage for canceling the noise current flowing through the parasitic capacitance between the high dv / dt node in the primary circuit and protective earth. The proposed shielding technique with balancing winding and the HPC method are verified by the experimental results.

Modelling and Design of a Low-Level Turn-to-Turn Fault Protection Scheme for Extra-High Voltage Magnetically Controlled Shunt Reactor

The objective of this paper is to model and design a low-level turn-to-turn fault (T2TF) protection scheme for a magnetically controlled shunt reactor (MCSR), during incipient stage under 10% to 100% operating capacity. Due to the structural and functional differences of all the three windings in extra-high voltage (EHV) MCSR, a separate mechanism of detecting a T2TF in each winding is necessary. For this purpose, a detailed mathematical and structural analysis of the model is performed, and a comprehensive protection scheme based on the internal changes in magnetic and electric parameters of the windings is formulated to detect 3% T2TF in power windings (PWs), control windings (CtrWs), compensation windings (CpWs), and to differentiate it from other abnormalities. The main idea of the scheme is to perform the currents magnitude comparison of respective winding with the predefined settings values and decide necessary action. The proposed scheme is also capable of identifying the faulty winding along with faulty phase. The scheme is tested under different operating capacities (10%, 50%, 100%), and other types of unusual conditions, i.e., direct energization, pre-excited energization, power regulation, internal and external faults. The results demonstrate the effectiveness of the proposed scheme. The work of this paper is applicable in the areas of power system transmission and power system protection. The simulations are carried out on MATLAB/Simulink-based models.

Analysis of a Novel Excitation Compensated Homopolar Inductor Alternator Used for Capacitor Charge Power Supply

For improving the power density of a homopolar inductor alternator (HIA) in a capacitor charge power supply (CCPS), a novel excitation compensation (EC) method is proposed in this article, wherein a compensation winding is installed in the HIA for providing pulse excitation and increasing the charge power. First, high-power and high-energy density requirements of the CCPS in the pulsed power supply (PPS) are presented, and the power density problem of the HIA caused by its homopolar structure is discussed. Second, methods for improving the charge power in the CCPS are studied, and a good way is to provide strong excitation to increase the machine electromotive force (EMF) during the charge process, whose difficulties are also studied. Third, a novel excitation-compensated HIA (ECHIA) is introduced and the principle and the effect of different EC circuits are analyzed. In the end, simulation results of the same size ECHIA and a conventional HIA show that the novel EC method can indeed improve the charge power in the CCPS and help the HIA achieve higher power density.

Reduction of the Detent Force in a Flux-Switching Permanent Magnet Linear Motor

In this paper, the detent force caused by the end effect in a flux-switching permanent magnet linear motor (FSPMLM) with six slots and five poles is investigated and reduced by two different methods. First, the detent force is diminished by adjusting the position of end teeth of primary side and injecting compensation current into compensation windings wound around the end teeth. Based on the linear relationship between compensation current and compensation force, the proper compensation current is derived and analyzed. Then, to avoid the magnetic coupling between compensation windings and phase windings, a novel compensation module with independent magnet circuit is presented and attached to the primary side of FSPMLM. Third, the two detent force reduction methods are compared with each other, and the compensation module is proved to be more effective. Finally, a prototype of FSPMLM with compensation modules is manufactured and tested to validate the proposed compensation method.

Novel protection scheme against turn-to-turn fault of magnetically controlled shunt reactor based on equivalent leakage inductance

Magnetically controlled shunt reactors (MCSRs) are key elements of extra-high voltage/ultra-high voltage (EHV/UHV) transmission systems for reactive power compensation and overvoltage suppression. Owing to the special core structure and winding connection mode, there is a complex electromagnetic relationship between faulty and non-faulty windings, which makes it challenging to accurately identify a turn-to-turn fault, which is the most common type of MCSR fault. To overcome this problem, a novel protection scheme is proposed by combining a start-up criterion with a fault discrimination criterion. The start-up criterion is based on the fundamental component of the total control current (itc) and the fault discrimination criterion is based on the identification of the equivalent leakage inductance (ELI). Firstly, based on the equivalent circuit of the power, control, and compensation windings, the corresponding ELI identification model is derived and solved using the recursive least squares (RLS) method. Subsequently, a fault discrimination scheme is derived based on the difference among three-phase ELIs. Finally, the proposed protection scheme is verified through simulations in MATLAB/Simulink and experiments on a physical model. The proposed scheme overcomes the limited sensitivity and reliability of conventional protection methods and can locate faulty windings, which is of great significance for the promotion of MCSRs and their applications in engineering.

A high accuracy fluxgate DC current sensor applicable to two-wire electric appliances

This paper presents a novel high-precision low noise self-oscillating fluxgate DC current sensor that can be used for two-wire measurement. This new sensor mainly consists of an EE-type ferromagnetic core, an oscillator, an inverter, six windings, sampling resistors, a feedback compensation circuit and a potential collection circuit. Two primary coils are placed in the hollow hole of the middle arm to realize the condition of fluxgate effect. The sensor still satisfies the average current model even when considering the mutual inductance among the windings. It can reach the ampere-turn balance by feedback and compensation to eventually achieve zero-flux detection. A new scheme to suppress secondary modulation ripple has been proposed by designing magnetic path and arranging the windings. In addition, researches have been conducted to study some relevant factors of eliminating secondary modulation ripple in this new way. Some relevant factors influencing the elimination of noise are simulated. The outcomes show that sum of the secondary modulation ripple voltage in the feedback compensation windings reaches a peak value of about 0.7 mV when the parameters of both circuits and magnetic path in the sensor’s left and right parts are symmetrical. And the more asymmetrical these parameters are, the larger ratio of suppressing noise is. That makes the sensor better perform under the condition of temperature drifting and decreases the influence of the error of both electric components and during the process of measurement.

Design and control of high‐capacity and low‐speed doubly fed start‐up permanent magnet synchronous motor

A novel rotor structure with a set of compensation winding for line-start permanent magnet synchronous motors for high capacity and low speed, which can meet the requirements of a ball mill with a high moment of inertia, is proposed to improve the motor-starting performance. A control strategy for the compensation winding current is implemented to increase the synchronisation ability with a high-inertia load. The compensation current and its control method are analysed using a mathematical model and verified using a time-step finite-element analysis. The simulation shows that the permanent magnet motor proposed in this study can successfully start at a load of 15 times rotor inertia.