Showing papers on "Rotor (electric) published in 2001"

Switched reluctance motor drives : modeling, simulation, analysis, design, and applications

Abstract: PRINCIPLE OF OPERATION OF THE SWITCH RELUCTANCE MOTOR (SRM) Introduction Background Elementary Operation of the Switch Reluctance Motor Principle of Operation of the Switched Reluctance Motor Derivation of the Relationship Between Inductance and Rotor Position Equivalent Circuit SRM Configurations Linear Switched Reluctance Machines References DERIVATION OF SRM CHARACTERISTICS Introduction Data for Performance Computation Analytic Method for the Computation of Machine Characteristics Computation of Unaligned Inductance Computation of Aligned Inductance Computation of Inductance vs. Rotor Position vs. Excitation Current Comparison of Measured, Analytic and Finite Element Results References DESIGN OF SRM Introduction Derivation of Output Equation Selection of Dimensions Design Verification Operational Limit Selection of Number of Phases Selection of Poles Ratio of Pole-Arc to Pole-Pitch Selection of Pole Base Selection of Pole-Arcs Measurement of Inductance Calculation of Torque Design of Linear Switched Reluctance Machine (LSRM) References CHAPTER 4: CONVERTERS FOR SRM DRIVES Converter Configurations Asymmetric Bridge Converter Asymmetric Converter Variation Single Switch per Phase Converters m Switches and 2m Diodes m Switches and 2m Diodes with Independent Phase Current Control (m+1) Switch and Diode Configurations One Common Switch Configuration Minimum Switch Topology With Variable DC Link Variable DC Link Voltage with Buck Boost Converter Topology 1.5m Switches and Diodes Configuration Comparison of Some Power Converters Two Stage Power Converter Resonant Converter Circuits for Switched Reluctance Motor Drives References CONTROL OF SRM DRIVE Introduction Control Principle Closed Loop Speed Controlled SRM Drive Design of Current Controllers Flux Linkage Controller Torque Control Design of the Speed Controller References MODELING AND SIMULATION OF SRM DRIVE SYSTEM Introduction Modeling Simulation References ACOUSTIC NOISE AND ITS CONTROL IN SRM Introduction Sources of Acoustic Noise in Electrical Machines Noise Sources Noise Mitigation Qualitative Design Measures to Reduce Noise Measurement of Acoustic Noise and Vibrations Future Directions Appendix-1: Derivation of First Mode Frequency of SRM References SENSORLESS OPERATION OF SRM DRIVES Introduction Current Sensing Rotor Position Measurement Methods Rotor Position Estimation References APPLICATION CONSIDERATIONS AND APPLICATIONS Introduction Review of SRM Drive Features for Application Consideration Applications Emerging applications References

A novel high-performance magnetic gear

Abstract: Mechanical gearboxes are used extensively to match the operating speed of prime-movers to the requirements of their loads. Although, high system torque densities can be achieved, gear lubrication and cooling are often required, whilst noise, vibration and reliability can be significant issues. The paper describes the design and performance of a magnetic gear, which employs rare-earth magnets, which simulation studies have shown to have a transmitted torque density exceeding 100 kNm/m/sup 3/.

Composite operation switch

Abstract: The present invention provides a composite operation switch that provides for more functions without increasing the number of switches and expanding its size, and provides satisfactory operability for switch selection operation. The composite operation switch includes: a housing that has a hollow ring-shape area and is provided with fixed contacts on an inside bottom face of the ring-shape area; a first rotor that is rotatably mounted in the housing and provided with movable contacts, which, upon rotation, contact or separate from the fixed contacts; a second rotor that is mounted in the first rotor and rotates together with the first rotor; and a multi-direction operation switch placed inside the hollow ring-shape area of the housing, wherein the second rotor is mounted in the first rotor so as to be vertically movable, and in the vicinity of the housing, a detecting switch is provided that detects a vertical movement position of the second rotor and outputs a signal for switching the types of selection functions of the multi-direction operation switch.

Dynamic modelling of a wind turbine with doubly fed induction generator

Abstract: As a result of increasing environmental concern, more and more electricity is generated from renewable sources. One way of generating electricity from renewable sources is to use wind turbines. A tendency to erect more and more wind turbines can be observed. As a result of this, in the near future wind turbines may start to influence the behaviour of electrical power systems. Therefore, adequate models to study the impact of wind turbines on electrical power system behaviour are needed. In this paper, a dynamic model of an important contemporary wind turbine concept is presented, namely a doubly fed (wound rotor) induction generator with a voltage source converter feeding the rotor. This wind turbine concept is equipped with rotor speed, pitch angle and terminal voltage controllers. After derivation of the model, the wind turbine response to two measured wind sequences is simulated.

Detection of Rotor Slot and Other Eccentricity-Related Harmonics in a Three-Phase Induction Motor with Different Rotor Cages

Abstract: Detection of rotor slot and other eccentricity related harmonics in the line current of a three phase induction motor is important both from the viewpoint of sensorless speed estimation as well as eccentricity related fault detection. However, it is now clear that not all three phase induction motors are capable of generating such harmonics in the line current. Recent research has shown that the presence of these harmonics is primarily dependent on the number of rotor slots and the number of fundamental pole pairs of the machine. While the number of fundamental pole pairs of a three phase induction motor usually is within one to four (higher pole pairs are generally avoided due to increased magnetizing current), the number of rotor slots can vary widely. The present paper investigates this phenomenon further and obtains a hitherto nebulous theoretical basis for the experimentally verified results. Detailed coupled magnetic circuit simulation results are presented for a four pole, three phase induction motor with 44, 43, and 42 rotor slots under healthy, static, dynamic and mixed eccentricity conditions. The simulation is flexible enough to accommodate other pole numbers also. These simulations are helpful in quantifying the predicted harmonics under different combinations of load, pole pair numbers, rotor slots and eccentricity conditions, thus making the problem easier for drive designers or diagnostic tools' developers. Data from three different induction machines, namely, a 4 pole, 44 bar, 3 hp, a 4 pole, 28 bar, 3 hp and a 2 pole, 39 bar, 100 hp motor have been used to verify the results experimentally. The simulation and the experimental results clearly validate the theoretical findings put forward in this paper.

Direct power control of grid-connected wound rotor induction machine without rotor position sensors

Abstract: A method is presented for fast response control of the torque and flux of a grid connected wound rotor induction machine fed by back to back connected voltage source inverters on the rotor side. It is based on the measurement of active and reactive power on the grid side where voltages and currents are alternating at fixed frequency. The active and reactive powers are made to track references using hysteresis controllers. The method eliminates the need for rotor position sensing and gives excellent dynamic performance, as shown by simulation and experimental results from a variable speed constant frequency induction generator system. It is also capable of starting on the fly. It is thus an attractive sensorless control method for drive as well as generator applications.

Systems and methods of electric motor control

Abstract: Apparatus and methods that control motor power in an electric motor such as a stepper motor, advantageously allow improved open-loop motor performance, allow reduced motor hunting, detect stalls, detect out-of-synchronization errors, control and synchronize multiple motors, and can automatically configure motor parameters to provide a motor with a power and load combination that gives an optimized performance. In one embodiment, an EMF commutation circuit detects a rotor position at which to sequence the motor to provide an optimized performance from the motor. In another embodiment, pulse width modulation (PWM) controls power, and the embodiment measures the rotor position within a detent position. Particular embodiments of the invention utilize a motor controller adapted to respond to a commutation signal, a pulse, or both in conjunction with a sensing device, such as an EMF detector or an optical encoder.

Permanent magnet motor

Abstract: PROBLEM TO BE SOLVED: To suppress vibrations in the thrust direction of a rotor core. SOLUTION: A rotor core 2 is formed in a structure, in which the core 2 is not brought into contact with a stator 1 by a shaft 3. Since the shaft 3 is loosely engaged with the core 2, the shaft 3 can move freely in its thrust direction. Thus, even if a magnetic field for moving the core 2 in the thrust direction is generated by the stator 1, only the core 2 is moved, its movement is not transmitted to the shaft 3, and a vibration of a fan mounted at the shaft 3 is suppressed.

Variable speed wind turbine having a matrix converter

Abstract: A variable speed wind turbine is disclosed comprising a turbine rotor that drives a doubly-fed induction generator, a matrix converter which converts variable frequency output into constant frequency output, and a control unit and a protection circuit for the matrix converter. Power is circulated in the system allowing for sensorless detection of rotor position and better output ratios of power from the system.

Active Balancing and Vibration Control of Rotating Machinery: A Survey

Abstract: Vibration suppression of rotating machinery is an important engineering problem. In this paper, a review of the research work performed in real-time active balanc- ing and active vibration control for rotating machinery, as well as the research work on dynamic modeling and analy- sis techniques of rotor systems, is presented. The basic methodology and a brief assessment of major difficulties and future research needs are also provided.

A simple position-sensorless algorithm for rotor-side field-oriented control of wound-rotor induction machine

Abstract: A simple position-sensorless method for the rotor-side field-oriented control of a wound-rotor induction machine is described in this paper. The algorithm is based on axis transformations. Compared to the previously proposed methods, it is more direct and the dependence on machine parameters is also largely reduced. The algorithm can be started on the fly without the knowledge of the initial rotor position. Operation at synchronous speed, corresponding to zero rotor frequency, is stable, thus making it suitable for variable speed constant frequency operations. Simulation and experimental results show excellent performance of the scheme.

Design and analysis of a new doubly salient permanent magnet motor

Abstract: This paper presents the design and analysis of a new doubly salient permanent magnet (DSPM) motor. The corresponding output power equation is analytically derived. The initial calculation of motor dimensions and parameters, namely, the core diameter, stack length, permanent magnet size, and winding turns, are also discussed. An 8/6-pole DSPM motor is designed and built for exemplification. Moreover, finite element analysis of this motor is carried out to investigate the magnetic field distribution at different rotor positions and load currents, in which the leakage flux outside the stator circumference of the DSPM motor is firstly taken into account. Hence, the characteristics of the proposed motor are deduced. Experimental results of the prototype are given to verify the theoretical analysis and to confirm its high efficiency.

Piezoelectric microactuators with substantially fixed axis of rotation and magnified stroke

Abstract: An actuator is coupled between a head and a flexure, the actuator providing submicron positioning of the head while reducing undesirable vibrations of the flexure. The actuator includes a stator and a rotor, with a plurality of deformable elements coupled between the stator and the rotor. In one aspect the rotor, stator and deformable elements are constructed so that the rotor has a substantially fixed axis of rotation relative to the stator, and the actuation of a transducer in the head is magnified. In another aspect the rotor is coupled to the head so that the axis of rotation is substantially aligned with the center of mass of the head and rotor, increasing the frequency at which the actuator can move the head and reducing vibrations in the flexure caused by actuation of the head.

Online stator fault diagnosis in induction motors

Abstract: This paper presents a noninvasive and online method for detection of stator winding faults in three-phase induction motors from observation of negative sequence supply current. A power decomposition technique (PDT) has been used to derive positive and negative sequence components of measured voltages and currents. A fault detection algorithm has been developed to characterise the effects of supply imbalance and nonlinear motor effects (motor iron saturation, winding imbalance, rotor static eccentricity), which also generate negative sequence current. The effects of motor heating and variation in negative sequence resistance with slip change are minimised by using only motor negative sequence reactance to calculate supply negative sequence current. Change in the motor negative sequence impedance under supply imbalance due to load variation (mainly because of closed rotor slots effect) has been included. Experimental results on several motors show that negative sequence impedance can vary between 10% to 50%. Semiempirical formulas based on theoretical and experimental results have been proposed to eliminate the effects of supply imbalance, load, and voltage variation. Compensation for this negative sequence current before making the fault decision enables a high fault sensitivity to be achieved.

Improved analysis of a bearingless switched reluctance motor

Abstract: Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. Bearingless switched reluctance motors have combined characteristics of switched reluctance motors and magnetic bearings. Production of radial force for rotor shaft magnetic suspension is explained with differential stator windings. Mathematical relations between motor currents and radial force are derived by considering cross coupling and fringing fluxes. Theoretical relationships are verified with experimental results at partial overlap positions.

A switched reluctance machine based starter/generator for more electric cars

Abstract: This paper addresses various aspects of the switched reluctance (SR) machine based starter/alternator (S/A) system for a more electric car. Inherent simplicity of the machine geometry and control, offering high efficiency and a very long constant power speed ratio along with a rugged structure and safe operation are among the most salient attributes of an SRM drive. In addition, due to the absence of any magnetic source on the rotor, a robust performance in the presence of high temperatures is expected. The authors also introduce a novel method in active damping of the engine torque pulsation by controlling the braking torque of the SRG. This will reduce the engine shaft pulsation thereby enhancing the durability of the system while presenting a quiet engine/generator combination. Furthermore, to enhance the compactness of the system components a novel method for control of the phase current is presented.

Design and implementation of the extended Kalman filter for the speed and rotor position estimation of brushless DC motor

Abstract: A method for speed and rotor position estimation of a brushless DC motor (BLDCM) is presented in this paper. An extended Kalman filter (EKF) is employed to estimate the motor state variables by only using measurements of the stator fine voltages and currents. When applying the EKF, it was necessary to solve some specific problems related to the voltage and current waveforms of the BLDCM. During the estimation procedure, the voltage- and current-measuring signals are not filtered, which is otherwise usually done when applying similar methods. The voltage average value during the sampling interval is obtained by combining measurements and calculations, owing to the application of the predictive current controller which is based on the mathematical model of motor. Two variants of the estimation algorithm are considered: (1) speed and rotor position are estimated with constant motor parameters and (2) the stator resistance is estimated simultaneously with motor state variables. In order to verify the estimation results, the laboratory setup has been constructed using a motor with ratings of 1.5 kW, 2000 r/min, fed by an insulated gate bipolar transistor inverter. The speed and current controls, as well as the estimation algorithm, have been implemented by a digital signal processor (TMS320C50). The experimental results show that is possible to estimate the speed and rotor position of the BLDCM with sufficient accuracy in both steady-state and dynamic operation. Introducing the estimation of the stator resistance, the speed estimation accuracy is increased, particularly at low speeds. At the end of the paper, the characteristics of the sensorless drive are analyzed. A sensorless speed control system has been achieved with maximum steady-state error between reference and actual motor speed of /spl plusmn/1% at speeds above 5% of the rated value.

Angular Focusing, Squeezing, and Rainbow Formation in a Strongly Driven Quantum Rotor

Abstract: Semiclassical catastrophes in the dynamics of a quantum rotor (molecule) driven by a strong time-varying field are considered. We show that for strong enough fields, a sharp peak in the rotor angular distribution can be achieved via a time-domain focusing phenomenon, followed by the formation of rainbowlike angular structures. A strategy leading to the enhanced angular squeezing is proposed that uses a specially designed sequence of pulses. The predicted effects can be observed in many processes, ranging from molecular alignment (orientation) by laser fields to heavy-ion collisions, and the trapping of cold atoms by a standing light wave.

Piezoelectric actuated optical switch

Abstract: An optical switching component comprises a rotor with a reflective top surface pivotally mounted within a stator, and a piezoelectric actuator set between the rotor and the stator to move the rotor about the pivot point. A controller can also be joined to the piezoelectric actuator to effectuate actuation thereof. Two light ports can also be set proximate to the reflective top surface such that a beam of light emitted from one is reflected to the other. Multiple optical switching components can be arranged to form an optical switching device. Optical switching components and devices can be fabricated according to conventional microfabrication practices including film deposition, planarization, and photolithography techniques.

Method and apparatus for transmitting information to the surface from a drill string down hole in a well

Abstract: A method and apparatus for transmitting information to the surface from down hole in a well in which a pulser (12) is incorporated into the bottom hole assembly of a drill string that generates pressure pulses (112) encoded to contain information concerning the drilling operation. The pressure pulses (112) travel to the surface where they are decoded so as to decipher the information. The pulser (12) includes a stator (38) forming passages through which drilling fluid flows on its way to the drill bit. The rotor (36) has blades that obstruct the flow of drilling fluid through the passages when the rotor (36) is rotated into a first orientation and that relieve the obstruction when rotated into a second orientation, so that oscillation of the rotor (36) generates the encoded pressure pulses (112). An electric motor (32), under the operation of a controller (26), drives a drive train that oscillates the rotor (36) between the first and second orientations. The controller (26) may receive instructions for controlling the pressure pulses characteristic from the surface by means of encoded pressure pulses transmitted to the pulser (12) from the surface that are sensed by the pressure sensor (29) and decoded by the controller (26).

Passive magnetic bearing for flywheel energy storage systems

Abstract: This paper proposes a novel type of passive noncontact magnetic suspension. An advantageous feature of passive suspension systems is that they are intrinsically stable, in contrast to active magnetic bearings and therefore can provide much higher reliability, which is known to be the crucial factor in applications requiring continuous noncontact suspension of high-speed rotors. An example of such an application is flywheel energy storage systems, which are considered to be an attractive alternative to conventional electrochemical batteries from both environmental and overall energy efficiency aspects. In such systems, a high-speed rotor is used to accumulate energy in the form of kinetic energy, and its continuous noncontact suspension may be needed for many years with no faults being tolerable. The suspension design addresses some drawbacks of other passive magnetic suspension systems, such as high rotational losses, high manufacturing accuracy, and dynamical problems. The authors have built and tested a bearing prototype, in which noncontact suspension of a 3.2 kg rotor is achieved when it rotates above 20 Hz.

X-ray CT scanner

Abstract: The rotary member carrying the X-ray radiation unfit and the X-ray detection unit and rotated around a subject is used as the rotor. The rotor is provided with a rotor core and a plurality of conductors connected to the core. The stator has at least one set of stator core and stator winding, the at least one set of stator core and stator winding being adapted to clamp the rotor and arranged at opposing positions. A three-phase AC current is supplied to the stator winding to generate a rotating magnetic field to rotate the rotor and thereby rotate the rotary member at high speed. Because the scan time can be reduced, the X-ray CT scanner can scan such moving organs as heart.

Design and control of an ultrasonic motor capable of generating multi-DOF motion

Abstract: A multi-degree-of-freedom (DOF) ultrasonic motor consisting of a bar-shaped stator and a spherical rotor was developed. It can generate 3-DOF rotation of the rotor around perpendicular axes using the bending vibration and longitudinal vibration of the stator, which is designed using the finite element analysis. From the simulated driving characteristics, a control method for the ultrasonic motor is proposed. Following this, the driving characteristics of the motor under both open-loop and closed-loop controls were measured experimentally. The multi-DOF position control of the rotor was achieved successfully using the proposed control method.

Rotor field oriented control of five-phase induction motor with the combined fundamental and third harmonic currents

Abstract: This paper presents an application of rotor field oriented control (RFOC) to a five-phase induction motor with the combined fundamental and third harmonic currents. Based on the motor model developed in a new d/sub 1/q/sub 1/d/sub 3/q/sub 3/n reference frame, the complete theory and modeling of rotor field oriented control of the five-phase induction motor are established. Specifically, investigation is made to improve power density and output torque of the five-phase induction motor by injecting third harmonic currents. By the proper dynamical adjustment and steady state compensation, the rotor field oriented control of the five-phase induction motor not only achieves a high drive performance, but also controls the fundamental and third harmonic flux and torque to generate the desired nearly rectangular air-gap flux. Both simulation and experimental results further verify the theoretical analysis and demonstrate the feasibility and practical value of the proposed five-phase induction motor drive.

Wind power installation

Abstract: The invention relates to a wind power installation. Modern wind power installations are regularly equipped with a lightning protection system. The aim of the invention is to avoid cited drawbacks and, in particular, to minimize the number of disturbances to the electronics caused by sparkovers occurring on the spark gaps. The invention also relates to a wind power installation comprising a device for continuously discharging electrostatic charge from at least one rotor blade of a wind power installation.

Brake device, and method for manufacturing the same

Abstract: PROBLEM TO BE SOLVED: To restrict deterioration of braking force in a brake device using friction force in such severe conditions under high temperature that fading phenomenon may occur generally. SOLUTION: A disc brake device for a bicycle as a device for braking a wheel rotated using friction force is provided with a disc rotor, a brake pad, and a nickel-tungsten alloy plating layer 91. The disc rotor is linked with the wheel to rotate. The brake pad makes friction with the disc rotor to brake the disc rotor. The nickel-tungsten alloy plating layer 91 is a plating layer formed on a friction surface of the disc rotor. COPYRIGHT: (C)2003,JPO

Application of a sliding-mode observer for position and speed estimation in switched reluctance motor drives

Abstract: A sliding-mode observer is applied toward the operation of a switched reluctance motor (SRM) drive. The sliding-mode observer estimates rotor position and velocity to control the conduction angles of the machine. Conventional on-off control with hysteresis current control is included with the position estimation scheme. The particular case of an automotive brake system motor is considered in detail where the conduction angles are modified with velocity feedback to provide optimum time response to brake system commands. Nonlinear modeling of a SRM is described and a computer simulation is developed based on data from an experimental SRM system. The sliding-mode observer is implemented with fixed-point and floating-point digital signal processors (DSPs) and the discrete-time implementations first examined under locked-rotor conditions. A comparison is also made between the implementation in two different types of DSPs. After confirming the accuracy of the computer simulation with experimental data, the design considerations in selecting observer coefficients with regard to sampling time, convergence rate, and transient stability are discussed. In conclusion, the effects of flux estimation errors on the system time response during a startup transient are examined.

Wind turbine system

Abstract: The present invention to an improved turbine used to convert wind into mechanical energy, more specifically, a long axis type of vertical-axis turbine allowing large columns of wind to be harnessed. These devices differ from horizontal-axis (propeller) type windmills which typically rotate about a vertical axis in order that they may face directly into a wind. The improvement includes constructing the components of the invention from lightweight materials which allow the enhanced conversion of wind kinetic energy into mechanical energy by the wind turbine. The preferred materials include honeycomb sandwich panels manufactured from non-metallic materials such as aramid fiber. The present invention is designed to be employed as a cost effective alternate power source in any wind from a breeze to a gale wind. To increase the structural integrity, the torque generating elements, namely, the rotor blades (2), are not directly attached to the shaft (11) but rather, they attach to the round top (10) and bottom rotor (4) cage plates through which torque forces generated can be transferred to the shaft (1). The unique design of an open cover on the top (10A) of the wind turbine allows wind from the direction above the turbine to be harnessed. The top shield structure has created a calm wind area between the shield and the top of the rotor cage that helps reduce turbidity and greatly facilitates wind exhaust from the system.