Showing papers on "Induction motor published in 2009"

Model Predictive Direct Torque Control—Part II: Implementation and Experimental Evaluation

Abstract: This paper describes the implementation of the model predictive direct torque control (MPDTC) algorithm for the control of three-phase induction motor drives comprising a three-level DC-link inverter. The MPDTC scheme is designed to keep the motor torque and stator flux and the inverter's neutral point potential within given hysteresis bounds while reducing the average switching frequency of the inverter, in comparison with the standard direct torque control (DTC) method. The algorithm is embedded in the control software environment of ABB's ACS6000 medium-voltage drive, and experimental results are provided which verify the advantageous features of MPDTC in terms of average inverter switching frequency reduction. More specifically, compared to standard DTC, the proposed MPDTC scheme achieves an average (over the whole operating range) reduction of the inverter switching frequency of 16.5%, but for specific operating conditions the reduction is as much as 37.4%.

A survey of condition monitoring and protection methods for medium voltage induction motors

Abstract: Medium voltage induction motors are widely used in industry and are essential to industrial processes. The breakdown of these medium voltage motors not only leads to high repair expenses, but also causes extraordinary financial losses due to unexpected downtime. To provide reliable condition monitoring and protection for medium voltage motors, this paper presents a comprehensive survey of the existing condition monitoring and protection methods in the following five areas: thermal protection and temperature estimation, stator insulation monitoring and fault detection, bearing fault detection, broken rotor bar/end-ring detection, and air-gap eccentricity detection. For each category, the related features of medium voltage motors are discussed; the effectiveness of the existing methods are discussed in terms of their robustness, accuracy and implementation complexity; recommendations for the future research in these areas are also presented.

Improved Resolution of the MCSA Method Via Hilbert Transform, Enabling the Diagnosis of Rotor Asymmetries at Very Low Slip

Abstract: This paper proposes an online/offline induction motor current signature analysis (MCSA) with advanced signal-and-data-processing algorithms, based on the Hilbert transform. MCSA is a method for motor diagnosis with stator-current signals. Although it is one of the most powerful online methods for diagnosing motor faults, it has some drawbacks that can degrade the performance and accuracy of a motor-diagnosis system. In particular, it is very difficult to detect broken rotor bars when the motor is operating at low slip or under no load, due to fast Fourier transform (FFT) frequency leakage and the small amplitude of the current components related to the fault. Therefore, advanced signal-and-data-processing algorithms are proposed. They consist of a proper sample selection algorithm, a Hilbert transformation of the stator-sampled current, and spectral analysis via FFT of the modulus of the resultant time-dependent vector modulus for achieving MCSA efficiently. Experimental results obtained on a 1.1 kW three-phase squirrel-cage induction motor are discussed.

An integral battery charger with Power Factor Correction for electric scooter

Abstract: This paper presents an integral battery charger for an electric scooter with high voltage batteries and interior-permanent-magnet motor traction drive. The battery charger is derived from the power hardware of the scooter, with the ac motor drive that operates as three-phase boost rectifier with power factor correction capability. The control of the charger is also integrated into the scooter control firmware that is implemented on a fixed-point DSP controller. Current-controlled or voltage-controlled charge modes are actuated according to the requirements of the battery management system, that is embedded into the battery pack. With respect to previous integrated chargers, the ac current is absorbed at unitary power factor with no harmonic distortion. Moreover, no additional filtering is needed since the pulsewidth modulation ripple is minimized by means of phase interleaving. The feasibility of the integral charger with different ac motors (induction motor, surface-mounted phase modulation motor) is also discussed, by means of a general model purposely developed for three-phase ac machines. The effectiveness of the proposed battery charger is experimentally demonstrated on a prototype electric scooter, equipped with two Li-ion battery packs rated 260 V, 20 Ah.

The Induction Machines Design Handbook

Abstract: Induction Machines: An Introduction Electric energy and induction motors A historical touch Induction machines in applications Construction Aspects and Operation Principles Construction aspects of rotary IMs Construction aspects of linear induction motors Operation principles of IMs Magnetic, Electric, and Insulation Materials for IM Soft magnetic materials Core (magnetic) losses Electrical conductors Insulation materials Induction Machine Windings and Their MMFs The ideal traveling mmf of ac windings A primitive single-layer winding A primitive two-layer chorded winding The mmf harmonics for integer q Rules for designing practical ac windings Basic fractional q three-phase ac windings Basic pole-changing three-phase ac windings Two-phase ac windings Pole-changing with single-phase supply induction motors Special topics on ac windings The mmf of rotor windings The "skewing" mmf concept The Magnetization Curve and Inductance Equivalent airgap to account for slotting Effective stack length The basic magnetization curve The emf in an ac winding The magnetization inductance Leakage Inductances and Resistances Leakage fields Differential leakage inductances Rectangular slot leakage inductance/single layer Rectangular slot leakage inductance/two layers Rounded shape slot leakage inductance/two layers Zig-zag airgap leakage inductances End-connection leakage inductance Skewing leakage inductance Rotor bar and end ring equivalent leakage inductance Basic phase resistance The cage rotor resistance Simplified leakage saturation corrections Reducing the rotor to stator Steady-State Equivalent Circuit and Performance Basic steady-state equivalent circuit Classification of operation modes Ideal no-load operation Short-circuit (zero speed) operation No-load motor operation The motor mode of operation Generating to power grid Autonomous induction generator mode The electromagnetic torque Efficiency and power factor Phasor diagrams: Standard and new Alternative equivalent circuits Unbalanced supply voltages One stator phase is open Unbalanced rotor windings One rotor phase is open When voltage varies around rated value When stator voltage have time harmonics Starting and Speed Control Methods Starting of cage-rotor induction motors Starting of wound-rotor induction motors Speed control methods for cage-rotor induction motors Variable frequency methods Speed control methods for wound rotor IMs Skin and On-Load Saturation Effects The skin effect Skin effects by the multilayer approach Skin effect in the end rings via the multilayer approach The double cage behaves like a deep bar cage Leakage flux path saturation-a simplified approach Leakage saturation and skin effects-a comprehensive analytical approach The FEM approach Standardized line-start induction motors Airgap Field Space Harmonics, Parasitic Torques, Radial Forces, and Noise Stator mmf produced airgap flux harmonics Airgap field of a squirrel cage winding Airgap conductance harmonics Leakage saturation influence on airgap conductance Main flux saturation influence on airgap conductance The harmonics-rich airgap flux density The eccentricity influence on airgap magnetic conductance Interactions of mmf (or step) harmonics and airgap magnetic conductance harmonics Parasitic torques Radial forces and electromagnetic noise Losses in Induction Machines Loss classifications Fundamental electromagnetic losses No-load space harmonics (stray no-load) losses in nonskewed IMs Load space harmonics (stray load) losses in nonskewed IMs Flux pulsation (stray) losses in skewed insulated bars Interbar current losses in uninsulated skewed rotor cages No-load rotor skewed uninsulated cage losses Load rotor skewed uninsulated cage losses Rules to reduce full load stray (space harmonics) losses High frequency time harmonics losses Computation of time harmonics conductor losses Time harmonics interbar rotor current losses Computation of time harmonic core losses Thermal Modeling and Cooling Some air cooling methods for IMs Conduction heat transfer Convection heat transfer Heat transfer by radiation Heat transport (thermal transients) in a homogenous body Induction motor thermal transients at stall Intermittent operation Temperature rise (TON) and fall (TOFF) times More realistic thermal equivalent circuits for IMs A detailed thermal equivalent circuit for transients Thermal equivalent circuit identification Thermal analysis through FEM Induction Machine Transients The phase coordinate model The complex variable model Steady state by the complex variable model Equivalent circuits for drives Electrical transients with flux linkages as variables Including magnetic saturation in the space phasor model Saturation and core loss inclusion into the state-space model Reduced order models The sudden short-circuit at terminals Most severe transients (so far) The abc-dq model for PWM inverter fed IMs First order models of IMs for steady-state stability in power systems Multimachine transients Subsynchronous resonance (SSR) The m/Nr actual winding modeling for transients Motor Specifications and Design Principles Typical load shaft torque/speed envelopes Derating due to voltage time harmonics Voltage and frequency variation Specifying induction motors for constant V and f Matching IMs to variable speed/torque loads Design factors Design features The output coefficient design concept The rotor tangential stress design concept IM Design Below 100KW and Constant V and f (Size Your Own IM) Design specifications by example The algorithm Main dimensions of stator core The stator winding Stator slot sizing Rotor slots The magnetization current Resistances and inductances Losses and efficiency Operation characteristics Temperature rise IM Design Above 100KW and Constant V and f (Size Your Own IM) High voltage stator design Low voltage stator design Deep bar cage rotor design Double cage rotor design Wound rotor design IM with wound rotor-performance computation Induction Machine Design for Variable Speed Power and voltage derating Reducing the skin effect in windings Torque pulsations reduction Increasing efficiency Increasing the breakdown torque Wide constant power speed range via voltage management Design for high and super-high speed applications Sample design approach for wide constant power speed range Optimization Design Essential optimization design methods The augmented Lagrangian multiplier method (ALMM) Sequential unconstrained minimization A modified Hooke-Jeeves method Genetic algorithms Three Phase Induction Generators Self-excited induction generator (SEIG) modeling Steady state performance of SEIG The second order slip equation model for steady state Steady state characteristics of SEIG for given speed and capacitor Parameter sensitivity in SEIG analysis Pole changing SEIGs Unbalanced steady state operation of SEIG Transient operation of SEIG SEIG transients with induction motor load Parallel operation of SEIGs The doubly-fed IG connected to the grid Linear Induction Generators Classifications and basic topologies Primary windings Transverse edge effect in double-sided LIM Transverse edge effect in single-sided LIM A technical theory of LIM longitudinal end effects Longitudinal end-effect waves and consequences Secondary power factor and efficiency The optimum goodness factor Linear flat induction actuators (no longitudinal end-effect) Tubular LIAs Short-secondary double-sided LIAs Linear induction motors for urban transportation Transients and control of LIMs Electromagnetic induction launchers Super-High Frequency Models and Behavior of IMs Three high frequency operation impedances The differential impedance Neutral and common mode impedance models The super-high frequency distributed equivalent circuit Bearing currents caused by PWM inverters Ways to reduce PWM inverter bearing currents Testing of Three-Phase IMs Loss segregation tests Efficiency measurements The temperature-rise test via forward short-circuit (FSC) method Parameter estimation tests Noise and vibration measurements: from no-load to load Single-Phase Induction Machines: The Basics Split-phase induction motors Capacitor induction motors The nature of stator-produced airgap field The fundamental mmf and its elliptic wave Forward-backward mmf waves The symmetrical components general model The d-q model The d-q model of star Steinmetz connection Single-Phase Induction Motors: Steady State Steady state performance with open auxiliary winding The split-phase and the capacitor IM: currents and torque Symmetrization conditions Starting torque and current inquires Typical motor characteristic Nonorthogonal stator windings Symmetrization conditions for nonorthogonal windings Mmf space harmonic parasitic torques Torque pulsations Inter-bar rotor currents Voltage harmonics effects The doubly tapped winding capacitor IM Single-Phase IM Transients The d-q model performance in stator coordinates Starting transients The multiple reference model for transients Including the space harmonics Single-Phase Induction Generators Steady state model and performance The d-q model for transients Expanding the operation range with power electronics Single-Phase IM Design Sizing the stator magnetic circuit Sizing the rotor magnetic circuit Sizing the stator windings Resistances and leakage reactances The magnetization reactance Xmm The starting torque and current Steady state performance around rated power Guidelines for a good design Optimization design issues Single-Phase IM Testing Loss segregation in split-phase and capacitor-start IMs The case of closed rotor slots Loss segregation in permanent capacitor IMs Speed (slip) measurements Load testing Complete torque-speed curve measurements Index

A Class of Speed-Sensorless Sliding-Mode Observers for High-Performance Induction Motor Drives

Abstract: A new family of speed-sensorless sliding-mode observers for induction motor drives has been developed. Three topologies are investigated in order to determine their feasibility, parameter sensitivity, and practical applicability. The most significant feature of all schemes is that they do not require the rotor speed adaptation, i.e., they are inherently sensorless observers. The most versatile and robust is a dual-reference-frame full-order flux observer. The other two schemes are flux observers implemented in stator frame and rotor frame, respectively. These are simpler than the first one and make use of the sliding-mode invariance over a specified range of modeling uncertainties and disturbances. Main theoretical aspects, results of parameter sensitivity analysis, and implementation details are given for each observer in order to allow the comparison. Experimental results with the dual-reference-frame observer, considered the most adequate for practical applications, are presented and discussed. Sensorless operation with a sliding-mode direct-torque-controlled drive at very low speeds is demonstrated. It is concluded that the new proposed observers represent a feasible alternative to the classical speed-adaptive flux observers.

Wide-Speed-Range Estimation With Online Parameter Identification Schemes of Sensorless Induction Motor Drives

Abstract: Recently, the development of speed estimation methods for sensorless control of induction motor drives has found great interest in the research community. Parameter adaptation schemes play an important role for better speed estimation over a wide range from zero to high levels beyond the rated speed. Therefore, parallel identification schemes for both speed and stator resistance of sensorless induction motor drives are proposed for a wide range of speed estimation. These estimation algorithms combine a sliding-mode current observer with Popov's hyperstability theory. Low- and zero-speed operations of the proposed sliding-mode-observer (SMO)-based speed estimation combined with an online stator resistance adaptation scheme are investigated. A modified SMO-based speed estimation scheme for field-weakening operation is also introduced. The mismatch problem of magnetizing inductance in the field-weakening region is treated by an online identification scheme. Magnetizing inductance, estimated in this way, is further utilized within the SMO, so that the main flux saturation variation is taken into consideration. The performance of the proposed SMO and its speed estimation accuracy, with an indirect field-oriented controlled induction motor, are verified by simulation and experimental results over a wide speed range from zero to high values beyond the base speed.

Sensorless Control of Induction Motor Drives at Very Low and Zero Speeds Using Neural Network Flux Observers

Abstract: A new method is described which considerably improves the performance of rotor flux model reference adaptive system (MRAS)-based sensorless drives in the critical low and zero speed regions of operation. It is applied to a vector-controlled induction motor drive and is experimentally verified. The new technique uses an artificial neural network (NN) as a rotor flux observer to replace the conventional voltage model. This makes the reference model free of pure integration and less sensitive to stator resistance variations. This is a radically different way of applying NNs to MRAS schemes. The data for training the NN are obtained from experimental measurements based on the current model avoiding voltage and flux sensors. This has the advantage of considering all drive nonlinearities. Both open- and closed-loop sensorless operations for the new scheme are investigated and compared with the conventional MRAS speed observer. The experimental results show great improvement in the speed estimation performance for open- and closed-loop operations, including zero speed.

Incipient Bearing Fault Detection via Motor Stator Current Noise Cancellation Using Wiener Filter

Abstract: Current-based monitoring can offer significant economic savings and implementation advantages over traditional vibration monitoring for bearing fault detection. The key issue in current-based bearing fault detection is to extract bearing fault signatures from the motor stator current. Since the bearing fault signature in the stator current is typically very subtle, particularly when the fault is at an incipient stage, it is difficult to detect the fault signature directly. Therefore, in this paper, the bearing fault signature is detected alternatively by estimating and removing nonbearing fault components via a noise cancellation method. In this method, all the components of the stator current that are not related to bearing faults are regarded as noise and are estimated by a Wiener filter. Then, all these noise components are cancelled out by their estimates in a real-time fashion, and a fault indicator is established based on the remaining components which are mainly caused by bearing faults. Machine parameters, bearing dimensions, nameplate values, and the stator current spectrum distribution are not required in the method. The results of online experiments with a 20-hp induction motor under multiple load levels have confirmed the effectiveness of this method.

Online Detection of Broken Rotor Bars in Induction Motors by Wavelet Packet Decomposition and Artificial Neural Networks

Abstract: We present an algorithm for the online detection of rotor bar breakage in induction motors through the use of wavelet packet decomposition (WPD) and neural networks. The system provides a feature representation of multiple frequency resolutions for faulty modes and accurately differentiates between healthy and faulty conditions, and its main applicability is to dynamic time-variant signals experienced in induction motors during run time. The algorithm analyzes rotor bar faults by WPD of the induction motor stator current. The extracted features with different frequency resolutions, together with the slip speed, are then used by a neural network trained for the detection of faults. The experimental results show that the proposed method is able to detect the faulty conditions with high accuracy.

Online Model-Based Stator-Fault Detection and Identification in Induction Motors

Abstract: In this paper, a model-based strategy for stator-interturn short-circuit detection on induction motors is presented. The proposed strategy is based on the generation of a vector of specific residual using a state observer. The vectorial residual is generated from a decomposition of the current estimation error. This allows for a fast detection of incipient faults, independently of the phase in which the fault occurs. Since the observer includes an adaptive scheme for rotor-speed estimation, the proposed scheme can be implemented for online monitoring, by measuring only stator voltages and currents. It is shown that the proposed strategy presents very low sensitivity to load variations and power-supply perturbations. Experimental results are included to show the ability of the proposed strategy for detecting incipient faults, including a low number of short-circuited turns and low fault current.

Reduced-order flux observers with stator-resistance adaptation for speed-sensorless induction motor drives

Abstract: This paper deals with reduced-order flux observers with stator-resistance adaptation for speed-sensorless induction motor drives. A general analytical solution for the stabilizing observer gain is given. The gain has two free positive parameters (which may depend on the operating point), whose selection significantly affects the damping, convergence rate, robustness, and other properties of the observer. The general stability conditions for the stator-resistance adaptation are derived. An observer design is proposed that yields a robust and well-damped system and requires a minimal amount of tuning work. The proposed observer design is experimentally tested using a 45-kW induction motor drive; stable operation at very low speeds under different loading conditions is demonstrated.

Natural Capacitor Voltage Balancing for a Flying Capacitor Converter Induction Motor Drive

Abstract: This paper presents an analysis of the natural voltage balancing dynamics of a three-phase flying capacitor converter when supplying an induction motor. The approach substitutes double Fourier harmonic series for the pulsewidth modulation switching waveforms and the frequency response of the motor, to create a linear state-space model of this type of load. The model requires the mid-frequency response (500 Hz-20 kHz) of the induction motor impedance to be identified, and takes skin and proximity effects into account by adding parallel R-L networks to a standard motor model. Model parameters were measured by applying FFT analysis to variable frequency square waves injected into the motor terminals, and fitting parameter values to these measurements using a least squares minimization method. From the analysis, it was found that the converter voltage balancing behavior degrades substantially at low motor speeds, and that a balance booster filter, as previously proposed, considerably improves the dynamic response. Experimental verification results using a scaled-down flying capacitor converter drive are included in the paper.

A Synchronous Current Control Scheme for Multiphase Induction Motor Drives

Abstract: Rotor-flux-oriented control of multiphase induction machines with sinusoidal magnetomotive force (MMF) distribution can be realized theoretically by using only two current controllers in the synchronous reference frame. In practice, however, this is inadequate, as shown in this paper using experimental results collected from five-phase induction motor drive laboratory prototypes. Various asymmetries of the machine and nonideal nature of the inverter necessitate an appropriate modification of the current control scheme in the rotating reference frame. Such a modified current control scheme is developed in this paper, and its ability to provide operation of the machine with a practically perfectly sinusoidal and balanced system of five-phase currents is demonstrated experimentally.

Demagnetization Analysis of Permanent Magnets According to Rotor Types of Interior Permanent Magnet Synchronous Motor

Abstract: This paper shows a study on the demagnetization performance analysis of permanent magnet according to three kinds of rotor types of an interior permanent magnet synchronous motor (IPMSM). It is very important to consider demagnetization performance as well as motor performance such as rated torque, output current, and efficiency when designing IPMSM. Three kinds of rotor types according to permanent magnet arrangement; single layer type, v shape type, and double layer type are generally used for IPMSM. In the paper, the magnetic equivalent circuits according to each rotor type are proposed in order for initial design of thickness of permanent magnets considering demagnetization by lumped constant related to magnetic circuit. The volume of permanent magnets per pole and back EMF of each rotor type is assumed to equal for the comparison of demagnetization of IPMSMs with same performance each other. Next, distribution of demagnetization in the permanent magnet is analyzed by using finite element method (FEM) for the verification of the results by magnetic equivalent circuit.

Vector control design and experimental evaluation for the brushless doubly fed machine

Abstract: A new vector control algorithm for the brushless doubly fed machine (BDFM) has been developed. The goal of BDFM control is to achieve a similar dynamic performance to the doubly fed induction machine (DFIM), exploiting the well-known induction motor vector control philosophy. For this purpose, a recently developed unified reference-frame model has been used to develop the vector control strategy. The theoretical considerations for the vector control design, control loops tuning and limits are shown. In addition, practical considerations for the experimental implementation of vector control for the BDFM are shown. Experimental results in a machine prototype confirm the good dynamic performances of this type of control.

Analysis of Output Current Ripple rms in Multiphase Drives Using Space Vector Approach

Abstract: Multiphase variable-speed drives, supplied from two-level voltage source inverters (VSIs), are nowadays considered for various industrial applications. Although numerous pulsewidth modulation (PWM) schemes for multiphase VSIs, aimed at sinusoidal output voltage generation, have been developed, no detailed analysis of the impact of these modulation schemes on the output current ripple has ever been reported. This paper presents a comprehensive analytical analysis and comparison of the output current ripple caused by the application of three different continuous PWM schemes, using a five-phase VSI as an example. Main properties of sinusoidal PWM, fifth harmonic injection PWM, and space vector PWM are elaborated and analyzed using the harmonic flux concept. Space vector theory is applied in the analysis. As a result, harmonic distortion factors are obtained for each PWM scheme. Theoretical considerations are verified by simulations and experimental investigation using a custom-designed five-phase VSI-fed induction motor drive.

Negative interference dominates collective transport of kinesin motors in the absence of load

Abstract: The collective function of motor proteins is known to be important for the directed transport of many intracellular cargos. However, understanding how multiple motors function as a group remains challenging and requires new methods that enable determination of both the exact number of motors participating in motility and their organization on subcellular cargos. Here we present a biosynthetic method that enables exactly two kinesin-1 molecules to be organized on linear scaffolds that separate the motors by a distance of 50 nm. Tracking the motions of these complexes revealed that while two motors produce longer average run lengths than single kinesins, the system effectively behaves as though a single-motor attachment state dominates motility. It is proposed that negative motor interference derived from asynchronous motor stepping and the communication of forces between motors leads to this behavior by promoting the rapid exchange between different microtubule-bound configurations of the assemblies.

On Sensorless Induction Motor Drives: Sliding-Mode Observer and Output Feedback Controller

Abstract: In this paper, a sensorless output feedback controller is designed in order to drive the induction motor (IM) without the use of flux and speed sensors. First, a new sliding-mode observer that uses only the measured stator currents is synthesized to estimate the speed, flux, and load torque. Second, a current-based field-oriented sliding-mode control is developed so as to steer the estimated speed and flux magnitude to the desired references. A stability analysis based on the Lyapunov theory is also presented in order to guarantee the closed-loop stability of the proposed observer-control system. Two experimental results for a 1.5-kW IM are presented and analyzed by taking into account the unobservability phenomena of the sensorless IM.

A High-Performance Line-Start Permanent Magnet Synchronous Motor Amended From a Small Industrial Three-Phase Induction Motor

Abstract: Small industrial three-phase induction motors (IMs) normally suffer from poor operational efficiency and power factor. This paper presents a high-performance line-start permanent magnet synchronous motor (LSPMSM) which is developed by simple modifications of an off-the-shelf small industrial three-phase IM with minimized additional costs. Two-dimensional (2-D) dynamic finite element analysis (FEA) models are employed to assess the machine performances, which are validated by comprehensive experimental results. The experimental comparisons between the amended LSPMSM and the original IM have indicated that significant improvements in efficiency and power factor can be achieved by the proposed LSPMSM.

A New Hybrid Random PWM Scheme

Abstract: This paper proposes a new hybrid random pulsewidth modulation (PWM) scheme based on a TMS320LF2407 DSP, in order to disperse the acoustic switching noise spectra of an induction motor drive. The proposed random PWM pulses are produced through the logical comparison of a pseudorandom binary sequence (PRBS) bits with the PWM pulses corresponding to two random triangular carriers. For this reason, the PWM pulses of the proposed scheme possess the hybrid characteristics of the random pulse position PWM and the random carrier frequency PWM. In order to verify the validity of the proposed method, the simulations and experiments were conducted with a 1.5-kW three-phase induction motor under the 2.5-A load condition. The DSP generates the random numbers, the PRBS bits with a lead-lag random bit (8 bit) and the three-phase reference signals. Also, a frequency modulator MAX038 makes the randomized frequency triangular carrier (3 plusmn 1 kHz). From the results, the proposed scheme shows good randomization effects of the voltage, current, and acoustic noise of the motor as compared with conventional scheme (3 kHz).

A wound-field three-phase flux-switching synchronous motor with all excitation sources on the stator

Abstract: A three-phase, segmental-rotor, flux-switching synchronous motor is presented for the first time, with both field and armature windings placed on the stator. Mutual coupling of the circuits is through segments whose motion causes switching of flux in the armature circuit. The magnetic geometry is substantially different to that of other flux-switching machines, and may offer advantages in terms of torque density and controllability. This paper describes the principles and the evaluation of a three-phase design, based on a 12-tooth stator with an 8-segment rotor before introducing a prototype machine and test results.

Minimization of Torque Ripple in PWM AC Drives

Abstract: A pulsewidth modulation (PWM) technique is proposed for minimizing the RMS torque ripple in inverter-fed induction motor drives subject to a given average switching frequency of the inverter. The proposed PWM technique is a combination of optimal continuous modulation and discontinuous modulation. The proposed technique is evaluated both theoretically as well as experimentally and is compared with well-known PWM techniques. It is shown that the proposed method reduces the RMS torque ripple by about 30% at the rated speed of the motor drive, compared to conventional space vector PWM.

Design and Analysis of Different Line-Start PM Synchronous Motors for Oil-Pump Applications

Abstract: This paper presents a comparison between three architectures of line-start PM motors for oil-pump application. This paper is focused on the performances in synchronous operation as well as the self-starting operations. Effects of electrical parameters on the starting and steady performance characteristics are demonstrated to find a satisfying design to meet required performances, it seems that the interior permanent magnet motor yields an impressive starting performance.

Comprehensive Eccentricity Fault Diagnosis in Induction Motors Using Finite Element Method

Abstract: Load variation along with static and dynamic eccentricities degrees is one of the major factors directly affecting the dynamic behaviors of eccentricity signatures as observed in the current spectrum of induction motors. Without taking the effect of load variation into consideration precisely, the change in the static and dynamic related fault signature amplitudes provides misleading information where the eccentricity degree and the load level exhibit similar effects in the current spectrum. In this paper, we address all these factors in a unified framework by analyzing various combinations both theoretically and experimentally. For this purpose, the time-stepping finite element method (TSFEM)-based, load-level-independent method is proposed to determine the static and dynamic eccentricities degrees individually.

Simultaneous State and Parameter Estimation in Induction Motors Using First- and Second-Order Sliding Modes

Abstract: We address the problem of meeting the requirements of controllers for the control of speed of induction motors, but under the constraint of not using speed and flux sensors: the so-called ldquosensorlessrdquo control problem. We offer an observer-based solution and present the design of two observers which provide motor speed, flux, and rotor resistance estimates simultaneously. Both observers, based on the rotor flux model in the stationary reference frame, are designed with inputs that enforce first- (conventional) and second-order sliding modes, respectively, on appropriately chosen switching surfaces. We present experimental results of the estimation procedure to demonstrate that only current and input voltage measurements are needed for accurate speed and flux estimation even in the presence of unknown parameters.

Modeling of Conducted EMI in Adjustable Speed Drives

Abstract: This paper deals with conducted electromagnetic interferences (EMIs) in adjustable-speed drive (ASD) systems. For some years, the use of high-speed switching power devices in ASDs induces high-voltage ( dv/dt) and high-current ( di/dt) variations that excite the parasitic elements of the power circuit, inducing conducted emissions. The advent of these devices has thus generated several unexpected problems, such as premature deterioration of motor ball bearings and high increases in the EMI levels, which are caused by the circulation of the high-frequency currents. In order to evaluate the level of the common-mode (CM) and the differential-mode (DM) currents in the ASD system, it is necessary to use a precise model of the pulse width modulation (PWM) inverter, power cable, and ac motor that takes into account various phenomena, which appear when the frequency increases. First, a PWM inverter and shielded four-wire power cable model are presented. Then, a new high-frequency modeling method of the ac motor is proposed. Finally, the ASD system is simulated and the obtained results are compared to the experimental measurements in the frequency and time domains.

Instantaneous Frequency of the Left Sideband Harmonic During the Start-Up Transient: A New Method for Diagnosis of Broken Bars

Abstract: In this paper, a new method for detecting the presence of broken rotor bars is presented. The proposed approach is valid for induction machines started at constant frequency and consists of extracting the instantaneous frequency (IF) of the left sideband harmonic (LSH) from the start-up current (LSHst), via the Hilbert transform. It is shown that, in the case of machines with one or several broken bars, the IF of the LSHst exhibits a very characteristic and easy to identify pattern, which is physically justified. This paper also shows that, if the IF of the LSHst is represented against the slip, a universal fault indicator (nondependent neither on the machine characteristics nor on the starting conditions) can be defined. This fault indicator consists of the correlation between the experimental IF of the LSHst and its theoretical evolution. This approach is theoretically introduced and experimentally validated by testing a commercial motor in faulty and healthy conditions, under different operating conditions.

A Dual Seven-Level Inverter Supply for an Open-End Winding Induction Motor Drive

Abstract: This paper develops a seven-level inverter structure for open-end winding induction motor drives. The inverter supply is realized by cascading four two-level and two three-level neutral-point-clamped inverters. The inverter control is designed in such a way that the common-mode voltage (CMV) is eliminated. DC-link capacitor voltage balancing is also achieved by using only the switching-state redundancies. The proposed power circuit structure is modular and therefore suitable for fault-tolerant applications. By appropriately isolating some of the inverters, the drive can be operated during fault conditions in a five-level or a three-level inverter mode, with preserved CMV elimination and DC-link capacitor voltage balancing, within a reduced modulation range.