Search

The purpose of this paper is to present a new Hybrid Analytical Model (HAM) based on Winding Function Theory (WFT) for electromagnetic analysis of the performance of one typical Unbalanced Two-Phase Induction Motor (UTPIM). Difierent indexes of electromagnetic modeling, such as winding distribution, slotting efiect, and magnetic saturation, can be accurately considered by using the proposed HAM. To obtain this new hybrid technique, WFT is reformulated to consider magnetic saturation in addition to the inuence of slotting and winding distribution. The Conformal Mappings (CMs) are used to calculate the slotted air-gap length accurately. The Magnetic Equivalent Circuit (MEC) model is used to consider the Magneto-Motive Force (MMF) drop in stator and rotor cores due to the excitation of one phase-winding. The results obtained from CMs and MEC are then utilized in reformulated WFT to calculate the inductances of the respective phase-winding. Transient analysis is then done to calculate the indexes of performance, such as air-gap magnetic field, phase currents, electromagnetic torque, and rotor speed, by using the lookup table of inductances while considering difierent capacitors in the auxiliary phase. In each step, the accuracy of analytical results is confirmed by comparing with corresponding results obtained from the Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

Abstract A new hybrid analytical model (HAM) based on conformal mapping (CM) method and magnetic equivalent circuit (MEC) model is presented in this paper for electromagnetic modelling of cage rotor induction motors (CRIMs) used in electric submersible pumps (ESPs). For every operating point, the iron parts are modelled with a non‐linear MEC model to calculate the equivalent virtual currents, which represent the influence of magneto motive force (MMF) drops and MMF sources in stator and rotor cores. The effects of the equivalent virtual currents on the air‐gap magnetic field are then considered using the CM method and Hague's solution. This approach for calculating the air‐gap field is also used to prepare a 3‐D lookup table (3‐D LUT) for each element of inductance matrix and derivative of inductance matrix in terms of rotor position. These LUTs are then used for transient modelling and analysis of CRIM under no‐load and loading conditions. The accuracy of proposed HAM is validated by comparing the results obtained through HAM with corresponding results obtained from finite element method and experiment set‐up.

In this article, the magnetic energy harvester (MEH) based on the current transformer is an innovative method to provide a potential solution for the power supply of sensor networks. Due to the current fluctuation and nonlinearity of the core, the harvester may produce insufficient power at low primary currents, while the core saturates at high primary currents. Aiming at resolving this problem, a novel method is proposed to improve the performance of MEH. In this method, a capacitor and two switches are used to store energy and modulate the core saturation. The performed analyses demonstrate that the proposed method enhances the harvested power under different primary current and load conditions. This is especially more pronounced at low primary currents and loads. It is found that for a low primary current of 2 Arms at 50 Hz, the harvested power increases by 206%. Moreover, applying this method can also reduce the load voltage by controlling the alternating on–off of the switches, thereby protecting the harvester in case of high primary currents. The theoretical calculation, circuit simulation, and experimental results demonstrate the effectiveness of this method. [ABSTRACT FROM AUTHOR]

This article proposes a simple method to calculate a current vector trajectory for the enhanced operation of the electric power generation system based on a synchronous reluctance machine (SynRM). Owing to magnetic saturation and cross magnetization, the performance and the torque capability of a SynRM vary according to the position and the value of the stator current. State-of-the-art control methods usually assume parameters with constant values, especially the inductance, neglecting saturation, leading to possible uncertainty in the machine operation. Therefore, a current vector trajectory to operate this type of machine, as a generator, in an extended speed range, with enhanced performance and considering magnetic saturation is proposed. A straightforward algorithm based on the inductance characteristic of the machine is used to calculate the trajectory of the stator current vector. This trajectory is evaluated via the numerical simulation of an experimentally validated finite-element model of a SynRM. The results show that the proposed current vector trajectory can improve the torque capability to 5% concerning the estimated trajectory without considering saturation. Experimental results are also provided to demonstrate the enhanced operation of the generator. [ABSTRACT FROM AUTHOR]

A new hybrid analytical model (HAM) based on conformal mapping (CM) method and magnetic equivalent circuit (MEC) model is presented in this paper for electromagnetic modelling of cage rotor induction motors (CRIMs) used in electric submersible pumps (ESPs). For every operating point, the iron parts are modelled with a non‐linear MEC model to calculate the equivalent virtual currents, which represent the influence of magneto motive force (MMF) drops and MMF sources in stator and rotor cores. The effects of the equivalent virtual currents on the air‐gap magnetic field are then considered using the CM method and Hague's solution. This approach for calculating the air‐gap field is also used to prepare a 3‐D lookup table (3‐D LUT) for each element of inductance matrix and derivative of inductance matrix in terms of rotor position. These LUTs are then used for transient modelling and analysis of CRIM under no‐load and loading conditions. The accuracy of proposed HAM is validated by comparing the results obtained through HAM with corresponding results obtained from finite element method and experiment set‐up. [ABSTRACT FROM AUTHOR]

Synchronous reluctance machine (SynRM) can be perceived as a special type of permanent magnet synchronous machine (PMSM), and shares similar control method, i.e. the sine-wave current drive with sinusoidal phase currents. In this paper, square-wave drive, which is employed for permanent magnet brushless (BLDC) motors, is employed for the SynRM, in order to economically reduce the cost of rotor position sensor. It is revealed that the torque density and efficiency are slightly sacrificed, whereas torque ripple is deteriorated, proving the SynRM with square-wave drive still promising for the cost-sensitive application if torque ripple is not considered as a critical issue. To further investigate the additional pulsating torque under square-wave drive, mathematical model based on a-b-c phase inductance and d-q axis inductance are established, together with the time-stepping FE calculated currents. It is concluded that the harmonics in the currents tend to cause non-sinusoidal variation of the magnetic reluctance, which can be represented as additional inductance harmonics. The harmonics of the current and inductance interact with each other, thus undesirable torque ripple components are produced.

In this study, we established the nonlinear model order reduction (MOR) of induction motors by parameterizing a multi-port Cauer ladder network (CLN). Appropriate parameters were selected to incorporate nonlinear magnetic characteristics. The parameterized multi-port CLN was applied to the transient analysis of a rotating induction motor. The proposed method reproduced the finite-element analysis results with various driving frequencies and slips. The parameterized multi-port CLN can effectively reduce the computation time for analyses requiring a large number of time steps. [ABSTRACT FROM AUTHOR]

Parameter identification of permanent magnet synchronous machines (PMSMs) is critical toward building an accurate machine model, achieving precise control, and improving operational reliability. This article proposes a decoupled estimation scheme for interior PMSM with consideration of magnetic saturation as nonlinear functions of current to improve the inductance estimation accuracy. An improved machine model considering magnetic saturation and cross-coupling effects by utilizing a quadratic model in inductance calculation is developed. Furthermore, the decoupled estimation scheme with considering stator resistance and iron loss resistance can effectively reduce the interaction in the process of parameter identification, and the least square algorithm is employed to improve the computational efficiency. Moreover, this proposed method is especially dedicated to the modern testing solutions that require complex hardware and extensive machine operation while being noninvasive by nature. [ABSTRACT FROM AUTHOR]

This paper deals with an analytical method to effectively calculate the inductance of an exterior-rotor switched reluctance motor (SRM), which evaluates the winding inductance of both the active section and the end section, accounting for the influence of core saturation. According to the inductance calculated by the analytical model, the flux linkage table and torque table can be established, and the steady state performance such as phase current, flux linkage, copper loss and core loss can be predicted. Effectiveness of this method is verified by the finite element method as well as by experimental results of a 12/8 SRM prototype.

Switched reluctance motors (SRMs) have recently attracted researchers’ attention owing to their robust mechanical construction, high thermal tolerance, and strong cost-effectiveness, which are promising for vehicle propulsion. However, they tend to generate large ripples in the torque and input currents to the inverter; this deteriorates the driving comfort, and damages the battery lifetime. Preceding articles have investigated using the phase currents of SRMs to eliminate these ripples. However, these articles had difficulties in sufficiently eliminating these ripples in operations under magnetic saturation. This article further evolves one of these preceding articles, and proposes a derivation method for the phase-current waveform for improving the elimination of the torque and input-current ripples in operation under magnetic saturation. The proposed method analytically determines the phase-current waveform based on a nonlinear behavior model of the SRM while considering the magnetic saturation. A finite-element-method-based simulation and experiment are performed to evaluate the proposed method. These results reveal the successful reduction of the torque and input-current ripples under the magnetic saturation relative to a preceding study, supporting the appropriateness of the proposed method. [ABSTRACT FROM AUTHOR]

Aiming at the slow calculation speed of the finite-element-analysis (FEA) method of the single-stage reluctance coil gun (RCG) and considering that the existing mathematical analysis method is not mature enough and the accuracy is low, this article constructed and summarized an advanced mathematical calculation model as a mathematical block diagram and implement the model in MATLAB/Simulink that can be used to optimize some circuit parameters of a coil launcher. On the one hand, the model switching from resistance–inductance–capacitance (RLC) to resistance–inductance circuit according to the actual application of the coil gun is established; on the other hand, the advantages of the FEA method are used to calculate the inductance, and a dynamic correction of inductance and inductance gradient according to the current value is proposed. The method is used to correct the deviation caused by the magnetic saturation problem. A comparison with the calculation data of the FEA method shows that the calculation of the constructed mathematical calculation model is basically correct and more efficient, and the expansion of the algorithmic function is easy to realize. [ABSTRACT FROM AUTHOR]

Substantial advantages of brushless doubly fed induction machine (BDFIM) bring up it as an interesting alternative for conventional solutions. In order to better analyze BDFIM performance, it is required to employ a more precise model of BDFIM. In this article, an approach, which completely relies on dynamic modeling in arbitrary reference frame, is proposed to consider both iron loss and main flux saturation effects in two-axis model of BDFIM. In this regard, the dynamic and static inductances are derived by using the magnetizing flux curve. If the cross-saturation is ignored, the time derivative of magnetizing inductances will yield incorrect simulation results. Therefore, to increase the accuracy, the proposed model contains terms that describe the cross-saturation effects. Due to the close relation between torque and power, the torque expression is also achieved in the presence of iron loss and magnetic saturation using expression of electrical input power. The simulation and experimental results are finally given to show the performance of the proposed model. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An improved winding function theory (IWFT) is presented in this article, which can be also used to calculate the self-inductance and mutual inductance of large air-gap electric machines, while accurately considering the air-gap length function and the magnetic saturation in iron parts, simultaneously. In IWFT, the radial length of flux path in different points inside air gap is calculated using the conformal mappings (CMs). The total air-gap length is the resultant of air-gap length at differential elements in the radial direction. A modified inverse air-gap function is then presented for a typical cage-rotor induction motor (CRIM) and a typical surface permanent magnet synchronous motor (SPMSM), which considers the real paths of flux lines in the slotted air gap. The high accuracy of these modified inverse air-gap functions is verified by comparing with the corresponding results obtained through the finite element method (FEM). To consider the magnetic saturation, a virtual winding function as a 2-D function is introduced in this article, which can consider the magneto-motive force (MMF) drops in iron parts of stator and rotor obtained through the magnetic equivalent circuit (MEC) model. By using IWFT, dependent on the structure of the relevant motor, a 2-D or 3-D lookup table is pre-calculated and stored for self/mutual inductances and their derivatives, and they are then used to model the running condition of CRIM and SPMSM under different loading conditions. Finally, the accuracy of IWFT results is verified by comparing them with the corresponding results obtained through FEM. [ABSTRACT FROM AUTHOR]

This article presents a novel method to improve energy scavenging from ac power lines under magnetic saturation conditions. The extracted power level of a conventional magnetic energy harvester is limited by the maximum flux density of the magnetic core. When a magnetic core is clamped on ac power lines, the flux density in the core is proportional to the magnetic field strength around the power line. Choosing a high-permeability core has the advantage of harvesting more energy for a given primary current. The flux density in such a core could reach its maximum value when the magnetic field increases. In this scenario, very little energy can be harvested since flux density variation in the core is small. Here we introduce an artificial magnetic field by adding an additional control coil to manipulate the magnetic field of power lines. A power management circuit is employed to store the energy harvested by the control coil and feed it back to the harvester to generate a counter magnetic field. As a result, the core will not be easily driven into the saturation region; hence, more energy can be harvested. Experimental results show that the proposed energy harvester can harvest an average power of 283 mW on a 50 Hz 10 Arms power line (2.34 mW/cm3/Arms), which is increased by 45% compared with the device without the control coil. This new method could provide a promising solution for smart grid monitoring and other industrial sensing applications. [ABSTRACT FROM AUTHOR]

This article proposes a compensation method for position estimation error under high-frequency signal-injection sensorless control (SISC), especially for heavily saturated interior permanent-magnet synchronous motors (IPMSMs). In the proposed method, the current reference is tilted so that the controller sees more desirable side of the inductance of IPMSM under control. With the proposed method, the position error can be fully compensated and the torque under SISC is limited not by the inductance characteristics of motor but current limit of the inverter and motor itself. Simulations and experiments are performed to verify the proposed method. [ABSTRACT FROM AUTHOR]

This article analyzes and discusses peak-current mode control (PCMC) in dc–dc voltage regulators using power inductors subjected to saturation. It is proved that the impact of inductors saturation on the operation of the PCMC regulators can be reliably predicted by means of the proposed mathematical model and technique. The results of circuit simulations and experimental measurements, regarding a dc–dc boost regulator, validate the theoretical analysis and the proposed model. The results confirm that the use of saturable inductors is a viable and reliable solution for PCMC regulators and demystify some concerns about the behavior of saturable inductors in the presence of line/load transients and overloads. [ABSTRACT FROM AUTHOR]

An online optimization-based optimal tracking control method to control IM drives in the entire speed and torque ranges is proposed in this article. The main feature of the proposed method is considering the nonlinear core saturation effects in generating the optimal reference currents in MTPA, field-weakening, and maximum torque per voltage (MTPV) regions. Constrained optimization problems are formulated and solved using Lagrange multipliers method to derive improved nonlinear MTPA and MTPV optimality conditions. Unlike most of the existing loss minimization methods in the literature, using optimal reference point look-up tables is avoided in the proposed method. Moreover, the effects of stator resistive drops, dc-link voltage variations, and inverter nonlinear voltage drop, which are usually neglected in the literature, are considered in generating optimal reference currents. A new straightforward and well-structured optimal reference point calculation scheme is proposed by dividing the operating plane of IM into four regions. The optimal reference currents in each region are then generated by solving the corresponding optimization problem. The smooth operation and transition of the proposed control method between MTPA and field-weakening regions are verified using simulations. The effectiveness of the proposed method is experimentally validated on a 4.7-kW, 4-pole, three-phase induction motor drive. [ABSTRACT FROM AUTHOR]

This paper deals with the high accurate current set-points solution for interior permanent-magnet synchronous motors (IPMSM) in wide-speed range applications. Considering voltage and current constraints, the operating regions can be divided into maximum torque per ampere, maximum current, field weakening, and maximum torque per voltage regions, which requires solving different nonlinear functions in real time to obtain optimal current set-points. Traditional methods including curve-fitting methods and polynomial approximation (PA) methods are not easy to obtain these solutions, especially involving magnetic saturation problems. In this paper, Newton–Raphson algorithm for improving the control accuracy of the current set-points is proposed. Meanwhile, parameters influence including magnetic saturation and resistive voltage drop is fully investigated. Compared with PA method, the proposed method is able to converge to accurate solutions in few numbers of iterations with reduced execution time, which can be easily implemented on an off-the-shelf digital signal processor. Both simulation results and experimental results on an 8-kW IPMSM rig are conducted showing good agreement with the expected results. [ABSTRACT FROM AUTHOR]

This paper deals with a dynamic model for three-phase induction machines equipped with closed rotor slots and deep rotor bars. The thin bridges closing the rotor slots saturate highly as a function of the rotor current. The impedance of the rotor bars also varies much as a function of the rotor current frequency. An extended dynamic model, which takes into account the slot-bridge saturation and the deep-bar effect, is developed. The model extensions can be plugged into a standard machine model and parametrized easily. The proposed model can be applied to time-domain simulations, real-time control, and identification. The model is validated by means of finite-element analysis and experiments using a four-pole 5.6-kW induction machine. The results show that the accuracy of the proposed model is superior to the standard model, particularly under transient excitation typically used in standstill self-commissioning tests of induction motor drives. [ABSTRACT FROM AUTHOR]

Offline parameter identification of permanent magnet synchronous machines (PMSMs) is of great importance for general-purpose drives with sensorless control. This paper proposes an amplitude-auto-adjusting signal injection (ASI) method for the parameter self-learning of PMSMs at standstill considering inverter nonlinearities and the digital time-delay effect. The ASI method achieves the inductance identification process under various dq-axis currents and at the same time prevents the unexpected rotor rotation during the self-commissioning process. For the test PMSM, the spatial inductance maps of dq-axes and abc-phases concerning the magnetic saturation and cross-coupling effects are identified along with the stator resistance. To enhance the estimation accuracy, an error model of the inverter nonlinearities in dq-axes is established, and a compensation method independent of inverter parameters is proposed based on the Hermite interpolation. In addition, the influence of the digital time-delay effect is analyzed and compensated based on the transient model of the circuits. The effectiveness of the proposed parameter self-learning scheme is confirmed on a 2.2-kW PMSM drive. The accuracy of the experimental results is validated by finite element analysis on the test machine. [ABSTRACT FROM AUTHOR]

This paper deals with the modelling of magnetic saturation in induction motors (IMs) with particular focus on the equivalent or fictitious air‐gap permeance technique. Besides, an improved version of this technique is provided so as to account for the transient starting process and the third harmonic saturation factor in addition to the fundamental one. This is for the symmetric case. Under air‐gap eccentricities, extension of both saturation models is proposed using the varying saturation factor solution. The 2D‐modified winding function approach (2D‐MWFA) is the base of the inductance calculation and the state equations are derived from the well‐known multiple coupled circuit model (MCCM). Thanks to such considerations, skew effect, rise of the magneto‐motive force (MMF) across the slots, all winding harmonics, and many faulty states can be judiciously taken into account. In summary, five derived saturation models are discussed in favour of a good handling of the saturation phenomenon in cage IMs. The work is supported by extensive simulation and experimental results of eccentricity, broken rotor bar, and combined faults. [ABSTRACT FROM AUTHOR]

In today's hybrid or fully electric vehicles, two types of propulsion machines can mainly be found: induction machines (IM) and interior permanent magnet synchronous machines. They are highly utilized and operated in magnetic saturation regions where inductance parameters change nonlinearly. The energy efficiency of both drives depends strongly on the choice of reference currents within field-oriented control. The paper shows two approaches for the determination of well-adjusted current components for both machines. First, model-based optimization is performed. It uses machine models considering saturation and loss models including the inverter. Second, a newly developed online-optimization scheme based on a discrete search method is presented. Simulation results show its advantages over recently published solutions for both machine types. Finally, experimental results at a drive test bench are presented. They prove the fast convergence and correct function of the proposed method. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents a novel pattern matching based position sensorless control method for IPMSMs. A target IPMSM for the proposed method is designed such that it has high power and torque density, while also being significantly influenced by magnetic saturation. As previously reported in papers , for IPMSMs, heavy magnetic saturation affects the spatial distribution of phase inductances according to rotor positions. Most position sensorless controls at low speeds typically depend on the assumption that phase inductances have sinusoidal spatial distribution according to rotor positions. Therefore, it is difficult to apply conventional methods to IPMSMs with heavy magnetic saturation. In the proposed method, rotor position is estimated by pattern matching using feature values, so that the phase inductances have unique and reproducible value according to rotor positions. While template data sets are required for the proposed method, the assumption for sinusoidal phase inductances is not. In this paper, the effect of magnetic saturation for position estimation based on conventional methods is discussed in Section 1 and 2. Then, details of the proposed method are shown in Section 3. In Section 4, results of experiments carried out in steady state and transient state are presented. The effectiveness of the proposed method is verified through the experiments. [ABSTRACT FROM AUTHOR]

There are many studies on magnetic levitation, some of which were already realized in railways. The authors in our laboratory now try to apply the magnetic levitation techniques to the steel processing industry. Therefore, we aim at the construction of magnetic levitation system for very thin steel plates. However, it is extremely difficult to levitate them perfectly, because of its vibratory properties and awkward electromagnetic properties. We have already studied the elasticity of the thin steel plate mechanically and shown its control methodology. In this research, we carry out many measurements about “the magnetic saturation and the magnetic leakage” and formulate its influence. Last, with a controller designed by considering the influence, we accomplish a stable levitation for a very thin steel plate. [ABSTRACT FROM AUTHOR]

This paper investigates torque ripple minimization for permanent-magnet synchronous machines (PMSM), and proposes a novel analytical solution of optimal stator current design for torque ripple minimization. The proposed design is theoretically proven to be able to minimize the torque ripple with minimal machine losses. Moreover, the optimal stator current is computed from analytical expression, which is computationally efficient. Therefore, the proposed approach is applicable for torque ripple minimization under both transient state and steady state. However, existing approaches usually employ optimization algorithm to optimize the stator current, which is computationally complex and involves iterative computation, so their applicability is limited under transient state, because the optimal stator current must be adaptively updated with respect to operating conditions. Moreover, magnetic saturation is considered in the proposed approach by employing a novel linear model to model the relation between the inductance and the stator current under maximum torque per ampere (MTPA) control. In this way, the proposed analytical solution does not involve inductance, and thus, the influence of magnetic saturation can be effectively reduced. The proposed approach is validated on a laboratory PMSM drive system under both transient state and steady state. [ABSTRACT FROM PUBLISHER]

In this paper, an analytical torque ripple model for interior permanent magnet synchronous machine (IPMSM) is introduced at first, which can be used to estimate the torque ripple. Then, the inductance variation due to magnetic saturation is analyzed through experimental investigations, which demonstrates that magnetic saturation has a great influence on the inductances, and hence the torque ripple minimization performance. Thus, this paper proposes an online parameter identification approach to estimate the inductances and incorporates them into the torque ripple minimization. The proposed parameter identification approach can estimate the dq-axis inductances accurately such that it brings significant torque ripple minimization improvement for IPMSMs. Numerical and experimental investigations have been conducted to validate the proposed approach based on a laboratory IPMSM. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of permanent magnet synchronous machine stator winding impedance variation in inter-turn short-circuit and eccentricity faults. The phase impedances are monitored through an extended self-commissioning procedure at the standstill mode before or after operation, and hence are agnostic to well-known issues caused by transients, load/speed level, or controller coefficient dependency. Moreover, the effect of stator iron core saturation on the electrical parameters is analyzed in depth. In order to distinguish the inter-turn shorts from the eccentricity fault which exhibits similar behaviors, a classification algorithm based on the saturation effect is introduced and analyzed on the machines with different pole-slot combinations. Both two-dimensional finite element analysis simulation and experimental test results are provided to show the efficacy of this analysis. [ABSTRACT FROM PUBLISHER]

The sideband current harmonics, as parasitic characteristics in permanent-magnet synchronous machine (PMSM) drives with space vector pulsewidth modulation technique, will increase the corresponding electromagnetic loss, torque ripple, vibration, and acoustic noises. Therefore, fast yet accurate evaluation of the resultant sideband current harmonic components is of particular importance during the design stage of the drive system. However, the inevitable magnetic saturation and cross-coupling effects in interior PMSM drives would have a significant impact on the current components, while the existing analytical sideband current harmonic model neglects those effects. This paper introduces a significant improvement on the analytical model by taking into account these effects with corresponding nonlinear factors. Experimental results are carried out to underpin the accuracy improvements of the predictions from the proposed model over the existing analytical one. The proposed model can offer a very detailed and insightful revelation of impacts of the magnetic saturation and cross-coupling effects on the corresponding sideband current harmonics. [ABSTRACT FROM PUBLISHER]

In this letter, an approach to eliminate the mutual flux effect on the rotor position estimation of switched reluctance motor drives without a priori knowledge of mutual flux is proposed, while operating in both linear and saturated magnetic regions. Considering magnetic saturation, the incremental-inductance estimation using the phase current slope difference method can be classified into three modes: Modes I-III. At positive-current-slope and negative-current-slope sampling point of one phase, the sign of current slope of the other phase changes in Modes I and II, but does not change in Mode III. Theoretically, the incremental-inductance estimation error introduced by the mutual flux is both rotor position and phase current dependent, which is ±1% to ±7% for the studied motor in Modes I and II. However, in Mode III, the mutual flux effect does not exist. Therefore, two methods are proposed to ensure that the incremental-inductance estimation is working in Mode III exclusively. The first one is variable-sampling incremental-inductance estimation for the outgoing phase and the other is the variable-hysteresis-band current control for the incoming phase. Simulation and experimental results show that the proposed method improves position estimation accuracy by 2° compared with the conventional method without variable-sampling and variable-hysteresis-band current control. [ABSTRACT FROM AUTHOR]

This paper presents two short-circuit fault models of a hybrid excitation flux switching permanent magnet machine, i.e., excitation phase short-circuit and interturn short-circuit in excitation windings. Two-dimensional finite element (FE) method is used to calculate the major parameters, such as armature and excitation inductances, which are not only functions of rotor position, but also of armature and excitation currents. Moreover, in case of short-circuits, the variations of armature and excitation currents are often significant. This in turn leads to an important change in winding inductances. Therefore, in order to precisely predict machine performance under short-circuit conditions, the use of inductances versus rotor position and RMS currents is essential. With the obtained FE results, two MATLAB/Simulink-based models are established. Then, the previously mentioned short-circuits have been studied and their influences on electromagnetic performances, such as armature and excitation currents, speed and torque, armature and excitation copper losses, stator and rotor core iron losses, as well as permanent magnet (PM) eddy current losses are analyzed. Experiments have been carried out to validate the simulations. [ABSTRACT FROM PUBLISHER]

The majority of the work performed for detecting eccentricity faults for permanent magnet synchronous motors (PMSM) focus on motor current signature analysis (MCSA), as it provides continuous online monitoring with existing current sensors. However, MCSA cannot be applied under nonstationary conditions and cannot distinguish faults with load torque oscillations, which are limitations for many PMSM drive applications. In this paper, it is shown that the d-axis inductance L decreases with an increase in the severity of eccentricity due to the change in the degree of magnetic saturation, and it is proposed as a new fault indicator. The inverter can be used to perform a standstill test automatically whenever the motor is stopped to measure L for eccentricity testing independent of load variations or oscillations, which is not possible with MCSA. An finite element and experimental study on a 10-hp PMSM verifies that eccentricity can be detected independent of the load with high sensitivity and reliability. [ABSTRACT FROM AUTHOR]

Condition monitoring of rotor problems such as demagnetization and eccentricity in permanent-magnet synchronous motors (PMSMs) is essential for guaranteeing high motor performance, efficiency, and reliability. However, there are many limitations to the offline and online methods currently used for PMSM rotor quality assessment. In this paper, an inverter-embedded technique for automated detection and classification of PMSM rotor faults is proposed as an alternative. The main concept is to use the inverter to perform a test whenever the motor is stopped and to detect rotor faults independent of operating conditions or load torque oscillations, which is not possible with motor current signature analysis (MCSA). The d -axis is excited with a direct-current+alternating-current signal, and the variation in the inductance pattern due to the change in the degree of magnetic saturation caused by demagnetization or eccentricity is observed for fault detection. An experimental study on a 7.5-kW PMSM verifies that demagnetization and eccentricity can be detected and classified independent of the load with high sensitivity. [ABSTRACT FROM PUBLISHER]

Accurate modeling of switched reluctance machines (SRMs) is necessary in order to achieve satisfactory control performance. Due to their highly nonlinear characteristics, the exact inductance profile for SRMs in one electrical period ought to be obtained. The purpose of this paper is to propose an accurate method to model the SRM magnetization characteristic, representing the accurate inductance profile, in order to achieve higher control performance. Furthermore, the innovative method proposed in this paper addresses a diverse way to minimize overall losses, compared to conventional methods. Instead of using a specific apparatus for measurement, the proposed method directly uses the saturation feature of the phase inductance. This paper discusses the advantages and improvements of the proposed method compared to conventional methods. Finally, the results computed by finite-element analysis are compared with the experimental results in terms of SRM magnetization characteristics. [ABSTRACT FROM AUTHOR]

The equivalent circuit constants of permanent magnet synchronous motors are needed in the calculation of operation characteristics, construction of a control system, etc. These constants can be computed from the data on structural form and materials. However, measurements are necessary to obtain highly precise values. Methods for measurement of the d- and q-axis inductances can be roughly divided into rotational and standstill methods. The standstill methods have the advantage that they are easy to carry out. However, it is difficult to consider magnetic saturation and distortion of the change in the armature winding inductance. The accuracy of the standstill method can be improved if these effects can be readily taken into account. This paper describes a standstill method for measuring accurate d- and q-axis synchronous inductances of permanent magnet synchronous motors. By utilizing the fact that the EMF interference terms in the motor voltage equation considering the distortion of the inductance change are equal to zero when the rotor is in a specific position, the proposed method determines the inductances considering both magnetic saturation and inductance distortion effects from simple off-line standstill testing. In addition, this method is capable of taking cross-magnetic saturation into account when used with the necessary testing equipment. The proposed method was implemented on a 0.4-kW interior permanent magnet synchronous motor with concentrated stator winding. The validity of the proposed method was demonstrated by comparing the measured and calculated results of the no-load and on-load characteristics. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 41–50, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20969 [ABSTRACT FROM AUTHOR]