Armature Field Research Articles

Iron Loss Calculation in Permanent Magnet Machines Under Unconventional Operations

This paper investigates the iron loss calculation of permanent magnet (PM) machines undertaking unconventional operations, where the high-frequency alternating armature field is only a fraction of the constant PM field. It is found that the iron loss of PM machines undertaking such unconventional operations cannot be calculated reliably as the conventional summation of all the iron loss harmonics predicted by finite-element (FE) methods due to fake iron loss harmonics. Further investigation is conducted on the influence of current frequency and magnitude, FE mesh, and convergence tolerance on the FE predicted iron loss under unconventional operations. It is then proposed in this paper that the iron loss of PM machines undertaking unconventional operations can be calculated as the summation of only the iron loss harmonics, which are insensitive to the convergence tolerance. The analyses are validated by the experimental results.

Multiply connected control systems of electric drives with field regulated reluctance machines

Owing to specific design features of the electric machine, i.e., a full-pitch winding, multiple phases, and freedom in selecting the phase current form, the functions of the excitation and the armature channels are distinctly separated in an electric drive with a field-regulated reluctance machine (FRRM), which enhances the regulation performance and the energy characteristic of the drive. A mathematical model of an electric drive that comprises an FRRM is given in the form of a block diagram. Attention is paid to the interaction between the excitation and the armature fields when the limiting energy-power characteristics of the drive are formed considering the magnetic saturation of the motor magnetic system. The advantage of the series excitation regime in reduction of total losses in the drive is demonstrated. The feedback channel synthesis in a multiloop control system is given. The features of formation of the processes in a multiengine electric drive with an FRRM are indicated.

DC motor speed control by self-tuning fuzzy PID algorithm

DC motors are used in industry extensively due to their high reliability, low cost, simple control of speed and position, low energy consumption and their compatibility with digital systems. There are different methods for controlling the speed of DC motors, mainly armature voltage or field control. In this paper, the speed of a separately excited DC motor is controlled by means of self-tuning fuzzy PID method. Against classic PID controllers in which the [Formula: see text], [Formula: see text] and [Formula: see text] values are constant, and are determined for a specific speed, in a self-tuning PID, [Formula: see text], [Formula: see text] and [Formula: see text] values are varied with the speed variations. In this paper, two distinct systems have been suggested for the control of DC motor. The output is examined and compared using the error and derivative error, or error and integrated error. After that, the most optimum regarding the overshoot value and settling time is selected. Finally, to reduce the overshoot value and the settling time of the system, we combined them. The presented method is simulated by means of the data from a DC motor in MATLAB software and the Simulink environment.

Speed Control of DC Motor Using PSO Tuned PI Controller

The control of DC motor system is difficult and mathematically tedious due to their high non linearity property. To overcome this difficulty, a new approach has been required. This paper presented a systematic procedure to develop PI based speed controller for DC motor. The designing of speed controller through state estimation approaches. The optimal parameter of PI controller is finding out by using PSO algorithms.The performances and characteristics of DC motor are observed. The simulation results verify that steady state error is reduced, the rising time is improved and the disturbances affect is reduced hence the better performances of DC motor. with a constant speed rotating field. It is observed that most of the industry is operating under stress condition further load parameter and control variable exhibit uncertainness in real practice and in fact these are random variables. Calculated values of load variable normally contain various inaccuracies. It has been observed that error may vary in the range of 5-10%. A few percentage error may be required tolerable in the area of the load speed controlling where these inaccuracies in the entire controller. In such situation minor inaccuracy in speed control are of little concern. Further the speed controller can always be designed to have sufficiently low effect on the non linearity of DC motor; so as to worst effect of parameter uncertainty can be accounted. In real time operation, the situation is different; design controller may encounter situation never imagined by designer before it took its present shape. Hence, in real time operation condition, risk of affecting nonlinearity of motor is always present. Here it is designed a controller which not affects the nonlinearity in DC motor. II. DcMotor The stator of the DC motor has poles, which are excited by DC current to produce Magnetic fields. The rotor has a ring-shaped laminated iron-core with slots. Coils with several turns are placed in the slots. The distance between the two legs of the coil is about 180 electric degrees. DC motors are characterized by their versatility. By means of various combinations of shunt, series and separately excited field winding they can be designed to display a wide variety of volt ampere or speed torque characteristics for both dynamic and steady state operation. The separately excited dc motor model is chosen for its good electrical and mechanical performances rather than other DC motor models. The DC motor is driven by applied voltage. In DC motor, the torque may be controlled by varying the armature current or field current. One of these is varied to control the torque while the other is held constant.

On-Load Cogging Torque Calculation in Permanent Magnet Machines

This paper investigates the on-load cogging torque calculation in permanent magnet (PM) machines. The vast majority of existing methods for calculating the cogging torque, no matter whether analytical or numerical methods, neglect the influence of load, or are inappropriate in considering the influence of load. Without using the frozen permeability method, the torque calculated by the virtual work principle includes the magnetic energy due to the armature field. When using the frozen permeability method, the resultant torque based on the Maxwell stress tensor with the on-load PM field only has nonzero average torque and, hence, is not the on-load cogging torque. A new on-load cogging torque calculation method is proposed in this paper based on the combination of the virtual work principle and frozen permeability method. For its implementation, an improved frozen permeability method, which makes the magnetic energy with on-load PM field that can only be calculated according to the B–H curve, is also developed. By using the new method, all the shortcomings of existing methods can be avoided and, hence, the on-load cogging torque can be calculated appropriately in both linear and nonlinear cases.

Average Torque Separation in Permanent Magnet Synchronous Machines Using Frozen Permeability

This paper investigates the average torque separation in permanent magnet (PM) synchronous machines. In order to accurately separate the PM and armature fields, and, hence, the torque components accounting for the magnetic saturation and crosscoupling, the frozen permeability (FP) method is often employed, while the torque can be calculated by different methods, such as Maxwell stress tensor and virtual work principle. Although these two methods result in identical torques in normal finite element (FE) analyses when appropriate FE meshes are used, the average torques calculated by these two methods are found to be different when the FP method is employed due to the influence of equivalent rotational magnetic saliency in the stator, which causes a part of PM torque being improperly attributed to the reluctance torque when Maxwell stress tensor method is employed. However, by using the virtual work principle, this is eliminated, and, hence, the average torque components can still be appropriately separated and analyzed.

A Fuzzy-Based Speed Control of DC Motor Using Combined Armature Voltage and Field Current

Abstract A direct current (DC) motor is supposed to be operated at an accurate and constant speed even if the load on the system is increased or decreased. This paper had controlled the DC motor's speed based on the fuzzy logic methods and simulated the fuzzy rules in Matlab/Simulink environment. Fuzzy Logic Controllers were proposed to achieve the speed control of a DC motor using combined armature voltage and field current by varying the armature voltage in the constant torque region and the field current in the constant power region. The fuzzy logic controllers were designed to be dependent on one another in such a way that the same set of rules were fired at the same time for the two controllers, having the same antecedences but different consequences. Simulation results show the effectiveness of the proposed method.

Demagnetization Control for Reliable Flux Weakening Control in PM Synchronous Machine

A process for permanent magnet (PM) demagnetization control for optimal and reliable flux weakening control in permanent magnet synchronous machines (PMSM) is presented. A physics-based model was developed to estimate the magnetic flux operating point of the PM poles during the operation of PMSM. The model is enabled to dynamically estimate the average and the partial PM demagnetization due to reverse armature field as well as the PM temperature rise. The model is a function of physical geometry and material of the PMSM, physics of demagnetization, and the ambient temperature. The demagnetization assessment and control is verified on a V-type PMSM using the modified FE-based coupled thermal-field-circuit phase variable model and the time step FE analysis.

Analytical magnetic field distribution of slotless brushless permanent magnet motors – Part I. Armature reaction field, inductance and rotor eddy current loss calculations

Two-dimensional analytical armature field calculations are presented for slotless permanent magnet brushless motors. The proposed method is applicable to both brushless AC and DC motors with any number of phases. The problem is formulated for eight annular regions: shaft, rotor back-iron, magnets, retaining sleeve, airspace, winding, stator back-iron and exterior. A general armature current density distribution is expressed as a function of spatial angle and time for any number of phases, any current waveform and any winding distribution. The governing partial differential equations of all the regions subject to a set of boundary conditions are represented and solved analytically for both internal and external rotor motors. Self- and mutual-inductance calculations as well as expressions for the calculation of rotor eddy current losses in the magnets, retaining sleeve and rotor back-iron are also represented. In the second part of these two papers, the open-circuit magnetic field is presented for different magnetisation patterns and subsequently the electromagnetic torque is calculated. The effectiveness of the analytical model is validated by comparing the results with those obtained from finite-element analyses as well as an experimental set-up which presented in the second part of the series.

Novel Design of Double-Stator Single-Rotor Magnetic-Geared Machines

In this paper, the concept of double stators and the concept of magnetic gears are artfully integrated to form a novel class of machines. By utilizing the modulation-ring structure, the proposed machines can modulate the high-speed rotating armature field of the stators to match the low-speed rotating permanent-magnet (PM) field of the rotor. Hence, the machines readily achieve the low-speed high-torque merit. In addition, the fractional-slot structure can be adopted for the inner-stator design to remove the modulation-ring of the inner stator. Two possible machine structures are discussed and compared. Their characteristics and performances are calculated by using the time-stepping finite-element-method. The results well verify the validity of the proposed machine design.

A Multipole Synchronous Machine With Nonoverlapping Concentrated Armature and Field Windings on the Stator

This paper presents a new type of multipole synchronous machine (SM) in which 2pa-pole armature and 2pf-pole field windings are centrally wound around individual stator teeth. The proposed machine operates as a (2pa + 2pf)-pole SM by providing a magnetic coupling between the armature and field windings through a 2pr-pole reluctance rotor. A 4-kVA (32 + 48)-pole prototype machine was designed and built to validate the principle of this structure. Performance characteristics of the prototype machine were simulated using 2-D finite-element analysis (FEA) and were supported by experiments. In addition, the effects of the rotor pole shape on the performance characteristics were studied through 2-D FEA simulations. The results presented provide guidelines for the optimum design of the proposed machine.

Robust Control of DC Motor Using Fuzzy Sliding Mode Control (FSMC)

Wide amplitude, DC motor's speed and their facile control cause its great application in industries. Generally the DC motors gain speed by armature voltage control or field control. The suggestion method in this paper is using sliding mode fuzzy control for DC motors robust control. The result is showing by use of this method we can't see any oscillation in responses and the time for reaching the normal speed is very short.

Robust Control Of Dc Motor Using Fuzzy Sliding Mode Control And Genetic Algorithm

Wide amplitude, DC motor's speed and their facile control cause its great application in industries. Generally the DC motors gain speed by armature voltage control or field control. In this paper, by using a combination of Fuzzy Sliding Mode methods and Genetic Algorithms, we have tired to optimally control the inverted pendulum by nonlinear equations. The results of this simulation have been mentioned in the conclusion. It seems that the results be acceptable results.

Comparison of Fault-Tolerant Operations for Permanent-Magnet Hybrid Brushless Motor Drive

The permanent-magnet hybrid brushless (PMHB) motor adopts both DC field windings and PMs for excitation. It not only offers effective online flux control, but also flexible brushless DC (BLDC) or brushless AC (BLAC) operations. The key of this paper is to investigate two remedial strategies for fault-tolerant operations of the PMHB motor drive under open-circuit faults. First, by utilizing field excitation boosting, the reduced torque due to one phase loss can be remedied, the so-called remedial BLDC operation mode. Second, by reconstructing armature fields due to the healthy phase currents, the reduced torque can also be remedied, the so-called remedial BLAC operation mode. Finally, these two remedial operation modes are compared and verified by experimentation, hence confirming the validity of the proposed fault-tolerant PMHB motor drive.

Effects of eddy currents due to a vacuum chamber wall in the airgap of a moving-magnet linear actuator

This paper discusses the effects of eddy currents induced in an electrically conducting plate which is placed in the airgap of a linear synchronous actuator with moving permanent magnets. The eddy currents induced in this plate, which is part of a controlled atmosphere chamber, cause not only damping but also deteriorate the actuator performance by disturbing the position measurement with Hall sensors. Furthermore, feed-forward controllers are less effective due to the suppression of high frequent armature fields. These effects are analyzed with an analytical model and verified with finite element simulations and measurements.

A fault location method using air‐gap fluxes of synchronous generator

AbstractThis paper deals with an experimental investigation of a novel fault location method using air‐gap flux distributions of a synchronous generator connected to a power system. Air‐gap fluxes are the sum of field fluxes and armature reaction fluxes. Changes in armature current and field current at a fault contribute directly to the armature reaction fluxes and field fluxes, then resultant air‐gap fluxes. Therefore, air‐gap fluxes can be utilized to locate a fault. Wavelet analysis is applied to the induced voltages of search coils, which are wound around a stator tooth top for measurement of the air‐gap flux. It is shown that the fault type and location can be estimated based on the change in the search coil voltages measured during the fault. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 20–27, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20707

A Novel Dual-Stator Hybrid Excited Synchronous Wind Generator

This paper presents a novel dual-stator hybrid excited synchronous wind generator and describes its structural features and operation principle. The no-load magnetic fields with different field currents are computed by 3-D finite-element method. Static characteristics, including the flux-linkage and EMF waveforms of stator windings, and inductance waveforms of armature windings and field winding, are analyzed. The simulation results show that due to the dual-stator structure, the air-gap magnetic flux can be easily controlled, while the output voltage can be increased effectively. Tests are performed on the prototype machine to validate the predicted results, and an excellent agreement is obtained.

同期発電機の空隙磁束を利用した送電線事故標定手法

This paper deals with an experimental investigation of a novel fault location method using air-gap flux distributions of a synchronous generator connected to a power system. Air-gap fluxes are the sum of field fluxes and armature reaction fluxes. Changes in armature current and field current at a fault contribute directly to the armature reaction fluxes and field fluxes, then resultant air-gap fluxes. Therefore, air-gap fluxes can be utilized to locate a fault. Wavelet analysis is applied to the induced voltages of search coils, which are wound around a stator tooth top for measurement of the air-gap flux. It is shown that the fault type and location can be estimated based on the change in the search coil voltages measured during the fault. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 20–27, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20707

Condition Monitoring of Brushless Three-Phase Synchronous Generators With Stator Winding or Rotor Circuit Deterioration

This paper presents experimental and theoretical analyses used to establish electrical features that can be utilized as indicators of armature winding, field winding, or rectifier diode deterioration in brushless three-phase synchronous generators before the imperfection progresses to become a ground fault. This paper begins with the description of a 5-kVA synchronous generator specifically designed and constructed to allow for simulation of armature winding, field winding, or rectifier diode deterioration in a brushless machine. Subsequently, a description of the experimental methodology and the results of experiments are presented. Specific features that can be used as indicators of the deterioration are described, and a theoretical basis for them is provided. The proposed features can be obtained continuously during normal generator operation. As such, they can be used as a basis for both brushless and brush-fed synchronous generator health monitoring applications

Analytical calculation of air-gap magnetic field distribution and instantaneous characteristics of brushless dc motors

This paper derives the relative air-gap-specific permeance distribution function by Schwarz-Christoffel transformation, considering the effect of slotting. Neglecting the iron saturation, and employing the analytical algorithm for partial differential equations, efficient and effective analytical calculations of no-load air-gap magnetic field distribution, armature field distribution, and phase electromotive force (EMF), are demonstrated, considering the stator slots. Subsequently, based on the main circuit topology of a brushless DC motor (BLDCM), the field-circuit coupling model is constructed for the motor, and then the phase current waveforms and load air-gap magnetic field distribution at any time are determined. Consequently, the instantaneous electromagnetic torque is computed, which underpins the quantitative analysis of torque ripple and the pulsation induced by commutation. Hence, the present work paves the way to precise prediction of the motor's performance and acoustic noise. It is a powerful tool for the design of surface permanent magnet brushless DC motors.