Magnetic Core Saturation Research Articles

Optimization of magnet arrangement in double‐layer interior permanent‐magnet motors

AbstractThe arrangement of permanent magnets in double‐layer interior permanent‐magnet motors is optimized for variable‐speed applications. First, the arrangement of magnets is decided by automatic optimization. Next, the superiority of the optimized motor is discussed by considering d‐ and q‐axis equivalent circuits that take into account the magnetic saturation of the rotor core. Finally, experimental verification is carried out with a prototype motor. It is confirmed that the maximum torque of the optimized motor under both low‐speed and high‐speed conditions is higher than that of conventional motors because of the relatively large q‐axis inductance and small d‐axis inductance. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 54–63, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22348

ANALYSIS OF HARMONIC COMPOSITION OF THE ALTERNATING MAGNETIC FIELD ASSOCIATED WITH THE ROTATING ROTOR OF TURBOGENERATOR IN THE NO-LOAD AND SHORT-CIRCUITS MODES

The method of calculation of the magnetic field alternating component at the surface of the rotating rotor of turbo generator is presented. It is based on multiposition of the numerical calculations of the magnetic field with the rotor turns and changes of currents in the stator winding. Discrete time functions of the alternating component of the magnetic induction are selected in points of the surface . The harmonic analysis is conducted for them. The developed method is universal in terms of excitation modes, designs and the magnetic core saturation. The theory is confirmed by computational researches in the no-load and short circuit modes of large turbo generator. In it, the alternating component of the magnetic induction on the rotor surface in the short-circuit mode is much greater than in the no-load mode. Values and harmonic composition of the alternating component of the magnetic induction differ substantially at different points of the rotor surface. Harmonics are ponderable in the range from the level determined by the phase structure of stator winding to the level determined by the tooth structure of its core. The results obtained are qualitatively fit into the classical notion of oscillatory processes of the magnetic field on the rotor surface, but now the value and harmonic composition of the alternating component of the magnetic induction receive adequate numerical filling. The result of work can be used for designing of a turbogenerators and other synchronous machines.

A generalized dynamical model for transformers with saturation and hysteresis effects

This article presents a new generalized non-linear dynamical model of a transformer with saturation and hysteresis effects. The structure of this new model is based on a magnetic equivalent circuit with non-linear reluctance elements. Using this method, accurate models of three- and five-legged transformers with magnetic saturation and hysteresis phenomena of iron core are introduced and inrush current in normal and sequential phase energization techniques are evaluated. Moreover, the effects of neutral resistance, magnetic structure and winding connections on inrush current are determined. In addition, for validation of the proposed model, some numerical simulations are made and compared with other techniques. Simulation results illustrate that the proposed model has high accuracy and efficiency for non-linear dynamical modelling of a transformer.

High-Impedance Bus Differential Protection Modeling in ATP/MODELS

This paper presents a modeling of a high-impedance bus differential protection logic using the ATP (Alternative Transients Program) MODELS language. The model is validated using ATP simulations on an electrical system consisting of a sectionalized bus arrangement with four transmission lines (TLs) and two autotransformers. The obtained results validate the model and present some of the advantages of using this type of bus protection, such as fast and safe operation, even when under adverse conditions such as current transformers (CTs) magnetic core saturation upon the occurrence of external faults.

Performance Analysis of ANN Training Algorithms to Detect the Magnetization Level in the Magnetic Core of a Welding Transformer

The aim of this study is to perform an analysis of the different ANN methods employed to detect the saturation level in the magnetic core of a welding transformer. The magnetization level detector is a substantial component of a middle-frequency direct current (MFDC) resistance spot welding system (RSWS). The basic circuit of a resistance spot welding system consists of an input rectifier, an inverter, a welding transformer, and a full-wave rectifier which is mounted on the output of the welding transformer. The presence of unbalanced resistances of the transformer secondary windings and the difference in characteristics of output rectifier diodes can cause the transformers magnetic core to become saturated. This produces spikes in the primary current and finally leads to the over-current protection switch-off of the entire system. To prevent the occurrence of such a phenomena, the welding system control must detect and maintain the magnetic core saturation within certain limits. Previously, an Artificial Neural Network based detector was proposed to detect the saturation level. In this paper, we will take an in depth look at the different ANN methods that can be employed, analyze them and then decide which is the best method based on factors such as computational time, algorithm complexity, root mean square error and the gradient obtained. Three algorithms in total are evaluated including Resilient-Back propagation, Levenberg-Marquardt, Gradient-Descent. Based on the results obtained, the Levenberg- Marquardt and the Resilient Back propagation were found to be the best algorithms but the Resilient Back propagation is preferred due to reasons such as computational time and algorithm complexity. In terms of RMSE both gave almost the same values. It is also shown that the Gradient Descent algorithm cannot be

Mechanical and Electrical Coupling Vibration Characteristic Analysis of Power Train System for Electric Driven Vehicle

Determine the electrical and mechanical coupling modeling and analysis method of power train system for electric driven vehicle. Mechanical vibration mathematical model, rotation DQ axis mathematical model of PMSM and electrical-mechanical coupling model of Power-train System for a new energy vehicle are given. Numerical solution and parameter sensitivity analysis has been done. Consider the impact of temperature change, iron core magnetic saturation, motor torque fluctuations and load torque fluctuation on the system.

인덕턴스의 포화현상을 이용한 IPMSM의 회전자 초기 위치 추정

본 논문에서는 매입형 영구자석 동기전동기의 정지 시 위치센서 없이 회전자의 초기 위치를 추정하는 방법을 제안한다. 제안된 방법은 자기적 포화에 의한 인덕턴스 변화를 이용하여 비교적 간단히 회전자의 초기 위치를 추정한다. 최소의 전압 벡터들을 인가하여 인덕턴스의 차이에 대응한 전류를 측정하여 회전자의 위치와 극성을 정확하게 판별할 수 있다. 제한된 방법은 추가적인 하드웨어가 필요하지 않으며, 전동기 파라미터에 영향을 받지 않고 전압벡터를 최소로 인가하여 측정할 수 있다는 장점을 가진다. 실험을 통해 제안된 방법의 타당성을 검증하였다. This paper proposes a new method to acquire an initial rotor position for IPMSM(Interior Permanent Magnet Synchronous Motor) without a position sensor at standstill. The proposed method is based on the variation of inductance caused by the magnetic saturation of stator core. Minimum number of voltage vectors are chosen to determine the initial rotor position. By using the resultant currents in combination with the inductance variation, the north pole and the absolute position of the rotor can be easily obtained. This method also has the advantage of not requiring motor parameters and additional hardware. Its validity is verified by experiments.

The Three-Phase Common-Mode Inductor: Modeling and Design Issues

This paper presents a comprehensive physical characterization and modeling of the three-phase common-mode (CM) inductors along with the equivalent circuits that are relevant for their design. Modeling issues that are treated sparsely in previous literature are explained in this paper, and novel insightful aspects are presented. The calculation of the leakage inductance is reviewed, along with the magnetic core saturation issues, and a new expression for the leakage flux path is derived. The influence of the core material characteristics on the performance of the component is discussed, and a new method for the selection of the material for the minimized volume CM inductors is proposed in order to simplify the design procedure. Experimental results which validate the model are presented.

Electronic Combined Transformer for Power-Quality Measurements in High-Voltage Systems

The evolution of electronic technology and digital signal processing is making competitive methods and devices for the design and the development of measurement transformers for high-voltage (HV) systems deeply different from those based on the traditional electromagnetic principle. Several advantages are offered by these new solutions: higher metrological characteristics, cost effectiveness, compact size, and lack of the typical problems of the traditional electromagnetic transformers (magnetic core saturation, magnetic resonance, bandwidth limits, etc.). In this paper, the design criteria adopted for the development of a prototype of a novel HV electronic combined transformer are presented. Its architecture permits the implementation of both voltage and current protective and measurement functions. The starting point is the employment of a mix of well-tested traditional technologies (like those used for the voltage capacitive divider and for the current sensor) and very sophisticated electronics. In particular, the electronic devices and the employed system architecture, beyond what is conceived for obtaining high measurement performances, are also oriented to provide advanced ancillary functions such as autodiagnosis, fault tolerance, autocalibration, etc. The developed combined measurement transformer features a rated primary voltage of 145/√3 kV and a rated primary current of 1000 A. Moreover, it is fully compliant with IEC 60044-7 and IEC 60044-8 standards, assuring 0.1 measurement precision class and satisfying also 5P and 3P protection classes for current and voltage sections, respectively.

二層IPMモータの磁石配置最適化

The arrangement of permanent magnets in double-layer interior permanent-magnet motors is optimized for variable-speed applications. First, the arrangement of magnets is decided by automatic optimization. Next, the superiority of the optimized motor is discussed by considering d- and q-axis equivalent circuits that take into account the magnetic saturation of the rotor core. Finally, experimental verification is carried out with a prototype motor. It is confirmed that the maximum torque of the optimized motor under both low-speed and high-speed conditions is higher than that of conventional motors because of the relatively large q-axis inductance and small d-axis inductance. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 54–63, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22348

Effect of Core Magnetic Saturation on Cogging Torque of Motor

This paper discusses what effects of magnetization saturation has on the cogging torques of 12-pole motors with 9-slot cores, using Nd-Fe-B ring magnets. The core flux density is changed with sintered, bonded and thermally demagnetized magnets. Cogging torques especially 36th harmonics, increase with the higher flux densities of the core at the teeth, and then magnetic saturation makes cogging torques larger. However, the harmonics of core flux densities are low although 36th cogging torques are related to the harmonics of core flux. Therefore, increasing cogging torques with magnetization saturations may be affected by the reduction in permeabilities due to magnetic saturations and the generation of core-flux density harmonics.

Artificial Neural Network Applied for Detection of Magnetization Level in the Magnetic Core of a Welding Transformer

This paper deals with the detection of saturation in the magnetic core of a welding transformer which is a part of a middle-frequency direct current (MFDC) resistance spot welding system (RSWS). It consists of an input rectifier, which produces dc bus voltage, an inverter, a welding transformer, and a full-wave rectifier that is mounted on the output of a transformer. During normal RSWS operation welding transformer's magnetic core can become saturated due to the unbalanced resistances of both transformer secondary windings and different characteristics of output rectifier diodes, which causes current spikes and over-current protection switch-off of the entire system. In order to prevent saturation of the transformer magnetic core, the RSWS control must detect that the magnetic core is approaching the saturated region. The aim of this paper is to present a reliable method for detection of magnetic core saturation that does not require an additional sensor. It is based on the artificial neural network (ANN). Its input is the measured primary current of the welding transformer. The applied ANN is trained to recognize the waveform of the current spikes in the primary current caused by the magnetic core saturation, which is used for magnetization level detection.

An Improved Magnetic Equivalent Circuit Model for Iron-Core Linear Permanent-Magnet Synchronous Motors

The aim of this work is to establish an accurate yet simple method for predicting flux density distribution and iron losses in linear permanent-magnet synchronous motors (LPMSMs) for iterative design procedures. For this purpose, an improved magnetic equivalent circuit for calculation of the teeth and yoke flux densities in the LPMSMs is presented. The magnetic saturation of iron core is considered by nonlinear elements and an iterative procedure is used to update these elements. The armature reaction is also taken into account in the modeling by flux sources located on the teeth of motors. These sources are time dependent and can model every winding configuration. The relative motion between the motor primary and secondary is considered by wisely designing air gap elements simplifying the permeance network construction and preventing permeance matrix distortion during primary motion. Flux densities in different load conditions are calculated by means of the proposed model. The effects of saturation and armature reaction on the flux density distribution are shown in detail. Using these flux densities, iron losses in the motor are examined and its variations versus motor parameters are then studied. All results obtained by proposed model are verified by finite-element method based on an extensive analysis.

An Experimental Investigation of Magnetic Saturation of a Transformer Type Superconducting Fault Current Limiter

The transformer type superconducting fault current limiter consists of a series transformer and a superconducting current limiting device. The primary winding of the transformer is connected in series with the power transmission line, and the secondary winding is short-circuited by the superconducting current limiting device. However, as the magnetic saturation of the transformer iron core affects the current limiting function, its detailed investigation is necessary.

Improvement on Current Limiting Characteristics of a Flux-Lock Type SFCL Using E-I Core

We investigated the current limiting characteristics of a flux-lock type superconducting fault current limiter (SFCL) using an E-I core. Unlike the flux-lock type SFCL using a two-legged common coil (C-C) core, two parallel connected coils and a high-TC superconducting (HTSC) element were placed on the left leg of a three-legged E-I core and an air gap was introduced into the central leg. Through the analyses for the fault current limiting experiments, the two parallel magnetic flux paths was confirmed to be contributed to the prevention of the magnetic saturation of the iron core and the improvement of the current limiting characteristics of the flux-lock type SFCL.

Equivalent Circuit Analysis of Interior Permanent Magnet Synchronous Motor Considering Magnetic saturation

Generally, design of the parts of an automobile is restricted by space especially components assembled in the engine room. Therefore traction motor for hybrid electric vehicle is designed by interior permanent magnet synchronous motor (IPMSM). The IPMSM has high power density and efficiency because it generates not only magnetic torque but also reluctance torque. However, IPMSM is difficult to design due to magnetic saturation and lots of analysis methods are required. Equivalent circuit analysis (ECA) is one of the design methods of IPMSM and it is generally used for characteristics analysis. Using the ECA, we can calculate the characteristics quickly. However, ECA can not estimate line current exactly because of saturation of magnetic core and flux weakening control. In order to perform the ECA exactly, calculation of parameters such as phase resistance, d- and q-axis inductance and no-load linkage flux are important. The phase resistance is simply calculated by using linear equation which is geometrical problem. However, dand q-axis inductance is nonlinear problem which is varied with current level and current angle. Therefore, nonlinear finite element analysis is necessary. Conventional ECA is considered only d- and q-axis inductance profile but no-load linkage flux is considered as constant value. However, no-load linkage flux of IPMSM is also varied according to current level and current angle similar with d- and q-axis inductance profile. Therefore, no-load linkage flux profile which is calculated case of current level and current angle should be considered in the ECA. In this paper, the calculation method of no-load linkage flux profile is introduced firstly and then characteristic of specific model is analyzed with proposed method. The result of line current from improved ECA is compared with experimental result and result of conventional ECA.

A novel starting method for BLDC motors without the position sensors

This paper presents a novel method to estimate the rotor position of a brushless dc (BLDC) motor at standstill. Moreover, a method for startup and acceleration of the motor up to a certain speed is introduced. The principle of the estimation method is based on the variation of the BLDC motor current in the magnetic axis due to the magnetic saturation of the stator core. An advantage of this method is that the maximum estimated error of the initial rotor position is 6°. Therefore, the motor starting torque is increased significantly. However, to implement this method, a current sensor at the dc link of the inverter is needed.

Analysis of an inverter-supplied multi-winding transformer with a full-wave rectifier at the output

This paper deals with the magnetic analysis of an inverter-supplied multi-winding transformer frequently used in resistance spot welding applications. The basic structure of the analyzed system consists of an inverter, a single-phase transformer with two secondary windings and a full-wave rectifier mounted at the output of the transformer, which assure a very short rise time of the welding current. The disturbing current spikes often appear in the transformer's primary in the steady-state operation, which can activate the over-current protection switch-off of the system. The results of numerical analysis performed on the nonlinear model of the discussed system have shown that very strong magnetic saturation of the transformer's iron core, caused by the interaction among the different ohmic resistances of secondary windings and different characteristics of the output rectifier diodes, provokes unwanted current spikes. Magnetic saturation could be efficiently eliminated using very simple passive method proposed in this paper. All findings are confirmed by systematic analysis numerically and experimentally.

Parametric variance consideration in speed control of single-phase flux reversal machine

The new flux reversal machine (FRM) has a simple robust rotor with a permanent magnet installed stator. However, the parameters of the FRM are dependant on the position of the rotor, operating temperature and magnetic saturation of the motor core. To obtain a robust performance in the speed control of the single-phase FRM, a control method that introduces an internal model of the motor is suggested for robustness against parameter variance and disturbance. The suggested control method is verified by both computer simulation and experiments and it is applied for popular AC induction/synchronous machines for their robust performance.

静止誘導器の開閉インパルス試験電圧波形の検討

In the switching impulse test of the transformers, magnetic saturation of core is produced when full test voltage is applied to the winding. The waveform then appearing is different from the waveform of the switching impulse test voltage which has been discussed in the standard waveform 250/2500 microseconds.On the reactor testing, damped oscillation discharge is generated when voltage of an impulse generator is applied to the winding since the inductance of the reactor is far below the exciting impedance of the transformer. In some cases, therefore, it is not possible to obtain the specified waveform in a large shunt reactor.This paper shows for determining a method the waveform of the switching impulse voltage and recommends the obtainable values of waveform parameters on reactors that wider tolerances may have to be accepted.