Showing papers on "Rotor (electric) published in 2003"

Modeling and control of a wind turbine driven doubly fed induction generator

Abstract: This paper presents the simulation results of a grid-connected wind driven doubly fed induction machine (DFIM) together with some real machine performance results. The modeling of the machine considers operating conditions below and above synchronous speed, which are actually achieved by means of a double-sided PWM converter joining the machine rotor to the grid. In order to decouple the active and reactive powers generated by the machine, stator-flux-oriented vector control is applied. The wind generator mathematical model developed in this paper is used to show how such a control strategy offers the possibility of controlling the power factor of the energy to be generated.

Architecture for electric machine

Abstract: The invention includes an electric machine having a rotor, stator and at least one winding in the stator adapted to conduct a current, and a secondary winding, electrically isolated from the first winding and inductively coupled to the first winding, which may be used to control at least one of the output voltage and current of the first winding.

Sensorless drive of surface-mounted permanent-magnet motor by high-frequency signal injection based on magnetic saliency

Abstract: This paper presents a new sensorless control scheme of a surface-mounted permanent-magnet (SMPM) motor using high-frequency voltage signal injection method based on the high-frequency impedance difference. In the SMPM motor, due to the flux of the permanent magnet, the stator core around the q-axis winding is saturated. This makes the magnetic saliency in the motor. This magnetic saliency has the information about the rotor position. The high-frequency voltage signal is injected into the motor in order to detect the magnetic saliency and estimate the rotor position. In this paper, the relationship between the high-frequency voltages and high-frequency currents is developed using the voltage equations at the high frequency, and the high-frequency impedance characteristics are analyzed experimentally under various conditions. The proposed sensorless control scheme makes it possible to drive the SMPM motor in the low-speed region including zero speed, even under heavy load conditions. The experimental results verify the performance of the proposed sensorless algorithm.

Electric machine having an integrally continuous stator winding and stator slot bridges

Abstract: The invention includes an electric machine having a rotor, stator and at least one winding in the stator adapted to conduct a current, and a secondary winding, electrically isolated from the first winding and inductively coupled to the first winding, which may be used to control at least one of the output voltage and current of the first winding.

Real-time stabilization and tracking of a four rotor mini-rotorcraft

Abstract: In this paper, we present a controller design and its implementation on a mini-rotorcraft having 4 rotors. The dynamic model is obtained via a Lagrange approach. Experiment results show good performance of the proposed non-linear controller based on nested saturation.

Potentials and limits of high speed PM motors

Abstract: This paper illustrates the potentials and limits of high-speed permanent-magnet (PM) motors. The effect of the material choice, including PM, stator core and retaining sleeve is highlighted. Slotted and slotless configurations are taken into account and compared, computing magnetic, electrical, mechanical and thermal quantities by means of both an analytical and a finite element approach. In particular, the thermal and the PM demagnetization limits and the rotor losses are evaluated. A criteria of optimisation of the motor structure is described, with the diameter ratio and the iron flux density as main design variables.

Sensorless rotor position estimation of an interior permanent-magnet motor from initial states

Abstract: This paper describes a torque, speed, or position control method at standstill and low speed in the interior permanent-magnet motor (IPMM) drive system without any rotational transducer. While IPMMs have originally magnetic saliency, it varies according to the load conditions and the control performance can be easily degraded. In this paper, the saliency or impedance difference is used as the conventional methods and, nevertheless, in order to amplify the difference containing the information of the rotor angle and to maintain a reasonable performance under any load condition a high-frequency injection scheme is proposed. A speed and position estimation scheme based on the characteristics of the high-frequency impedance is proposed. The scheme extracts the high-frequency impedance components related to the rotor position. An initial angle estimation scheme for starting from an arbitrary rotor position is also proposed. It can distinguish the north magnetic pole position from the south one in several decade milliseconds. The proposed scheme enables position control of a transducerless or position-sensorless IPMM. The experimental results clarify the satisfactory operation of the proposed position control algorithm under any load condition.

On-line dead-time compensation method using disturbance observer

Abstract: A new on-line dead-time compensation method for a permanent magnet (PM) synchronous motor drive is proposed. Using a simple disturbance observer without any additional circuit and off-line experimental measurement, disturbance voltages in the rotor reference dq frame caused by the dead time and nonideal switching characteristics of power devices are estimated in an on-line manner and fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Simulations and experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method.

A sensorless, stable V/f control method for permanent-magnet synchronous motor drives

Abstract: When permanent-magnet synchronous motors (PMSMs) are used for pump and fan applications, V/f control methods can be used to control them. The problem with open-loop V/f control of PMSMs without having damper windings in the rotor is the inherent instability after exceeding a certain applied frequency. In this paper, a new V/f control method is proposed for motor drives for stable operation in a wide frequency range. The magnitude of the voltage is controlled in order to maintain a constant stator flux linkage in the PMSM. The applied frequency is modulated proportional to the input power perturbations to stabilize the drive for a wide frequency range. No position sensor is required to implement this stabilizing technique. The small-signal analysis and the experimental results confirm the effectiveness of this stabilizing technique. The experimental results also indicate the satisfactory performance of the drive for pump and fan applications.

Current signature analysis of induction motor mechanical faults by wavelet packet decomposition

Abstract: This paper presents a novel approach to induction motor current signature analysis based on wavelet packet decomposition (WPD) of the stator current. The novelty of the proposed method lies in the fact that by using WPD method the inherent nonstationary nature of stator current can be accurately considered. The key characteristics of the proposed method are its ability to provide feature representations of multiple frequency resolutions for faulty modes, ability to clearly differentiate between healthy and faulty conditions, and its applicability to nonstationary signals. Successful implementation of the system for two types of faults, i.e., rotor bar breakage and air-gap eccentricity is demonstrated here. The results are validated based on both simulation and experiments of a 5-hp induction motor.

Inverter nonlinearity effects in high frequency signal injection-based, sensorless control methods

Abstract: An analysis of pulsewidth-modulation inverter nonlinearities influencing high-frequency carrier-signal voltage injection for saliency-tracking-based rotor/flux position estimation is presented in this paper. Distortion of the injected carrier voltage caused by the nonlinear behavior of the inverter has been reported to cause errors in the estimated rotor/flux position. Though a number of techniques have been developed to compensate for inverter nonlinearities, they have not been proven to be effective when a high-frequency low-magnitude voltage needs to be generated. Both the origins of the distortion as well as the requirements for compensation methods to be effective when producing such high-frequency voltages will be established in this paper.

A new algorithm for transient motor current signature analysis using wavelets

Abstract: A new algorithm is introduced for motor current signature analysis of induction machines operating during transients. The algorithm is able to extract the amplitude, phase and frequency of a single sinusoid embedded in a nonstationary waveform. The algorithm is applied to the detection of broken rotor bars in induction machines during startup transients. The fundamental component of current, which varies in amplitude, phase, and frequency, is extracted using the algorithm. The residual current is then analyzed using wavelets for the detection of broken rotor bars. This method of condition monitoring does not require parameters such as speed or number of rotor bars, is not load dependent and can be applied to motors that operate continuously in the transient mode, e.g., wind generators or motor-operated valves.

An integrated flywheel energy storage system with homopolar inductor motor/generator and high-frequency drive

Abstract: The design, construction, and test of an integrated flywheel energy storage system with a homopolar inductor motor/generator and high-frequency drive is presented in this paper. The work is presented as an integrated design of flywheel system, motor, drive, and controller. The motor design features low rotor losses, a slotless stator, construction from robust and low cost materials, and a rotor that also serves as the energy storage rotor for the flywheel system. A high-frequency six-step drive scheme is used in place of pulsewidth modulation because of the high electrical frequencies. A speed-sensorless controller that works without state estimation is also described. A prototype of the flywheel system has been demonstrated at a power level of 9.4 kW, with an average system efficiency of 83% over a 30000-60000 r/min speed range.

Initial rotor position estimation of an interior permanent magnet synchronous machine using carrier-frequency injection methods

Abstract: This paper presents a method using carrier frequency injection to estimate the initial rotor position and magnet polarity for an interior permanent magnet synchronous machine. A non-saturating inductance model of the machine provides no information about the polarity of the rotor magnet because the position observer based on this model is locally stable at both poles. To distinguish the polarity of the rotor magnet, the magnetic saturation effect can be used. A 2/sup nd/ order Taylor series can be used to describe the nonlinear magnetic saturation relationship between the current and the flux linkage in the d-axis rotor reference frame. The 2/sup nd/ order term produces the 2/sup nd/ harmonic component of the carrier frequency, and the sign of its coefficient identifies the polarity of the rotor magnet being tracked. Both simulation and experimental results show good response of the position observer at rotor electrical positions of /spl plusmn/0.5/spl pi/ rad using either a rotating vector in the stationary reference frame or a pulsating vector in the estimated rotor reference frame.

Method of operating a wind turbine

Abstract: A wind turbine has a generator (7) with a connected rotor (3) having a hub (4) and blades (5) rotatably connected to the hub for adjusting the pitch angle. In a method of operating such a wind turbine under climatic conditions, where there is a risk of icing on the blades and no or weak wind, the generator is used as a motor for driving the rotor and the pitch angle of the blades is adjusted to ensure that the resulting wind substantially hits the leading edge of the blades. Any ice formed may be removed by means of de-icing in a known manner.

Electrostatically Levitated Ring-Shaped Rotational-Gyro/Accelerometer

Abstract: This paper reports an electrostatically levitated inertia measurement system which is based on the principle of a rotational gyro. The device has several advantages: the levitation of the rotor in a vacuum eliminates mechanical friction resulting in high sensitivity; the position control for the levitation allows accelerations to be sensed in the tri-axis; and the fabrication of the device by a micromachining technique has the cost advantages afforded by miniaturization. Latest measurements yield a noise floor of the gyro and that of the accelerometer as low as 0.15 deg/h1/2 and 30 µG/Hz1/2, respectively. This performance is achieved by a new sensor design. To further improve of the previous device, a ring-shaped structure is designed and fabricated by deep reactive ion etching using inductively coupled plasma. The rotor levitation is performed with capacitive detection and electrostatic actuation. Multiaxis closed-loop control is realized by differential capacitance sensing and frequency multiplying. The rotation of the micro gyro is based on the principle of a planar variable capacitance motor.

Control of DFIG wind turbines

Abstract: The generation of electrical power using sustainable sources of energy is developing rapidly. The authors describe how the security and quality of electricity supply might be maintained. They discuss the control of variable speed using doubly fed induction generators (DFIG) in wind turbines. The DFIG is constructed from a wound rotor asynchronous machine. Variable speed operation is obtained by injecting a variable voltage into the rotor at slip frequency The injected rotor voltage is obtained using two AC/DC insulated gate bipolar transistor based voltage source converters (VSC), linked by a DC bus. The converter ratings determine the variable speed range. Speed control for optimum power, system frequency control, and machine inertia are also discussed.

Modeling of the UAE Wind Turbine for Refinement of FAST{_}AD

Abstract: The Unsteady Aerodynamics Experiment (UAE) research wind turbine was modeled both aerodynamically and structurally in the FAST{_}AD wind turbine design code, and its response to wind inflows was simulated for a sample of test cases. A study was conducted to determine why wind turbine load magnitude discrepancies-inconsistencies in aerodynamic force coefficients, rotor shaft torque, and out-of-plane bending moments at the blade root across a range of operating conditions-exist between load predictions made by FAST{_}AD and other modeling tools and measured loads taken from the actual UAE wind turbine during the NASA-Ames wind tunnel tests. The acquired experimental test data represent the finest, most accurate set of wind turbine aerodynamic and induced flow field data available today. A sample of the FAST{_}AD model input parameters most critical to the aerodynamics computations was also systematically perturbed to determine their effect on load and performance predictions. Attention was focused on the simpler upwind rotor configuration, zero yaw error test cases. Inconsistencies in input file parameters, such as aerodynamic performance characteristics, explain a noteworthy fraction of the load prediction discrepancies of the various modeling tools.

Permanent magnet rotating electric machine

Abstract: PROBLEM TO BE SOLVED: To provide a permanent magnet rotating electric machine which can prevent a permanent magnet from being cracked even when the permanent magnet is magnetized. SOLUTION: The permanent magnet rotating electric machine includes a rotor core 32A in which two circumferential grooves 32C are formed toward a circumferential direction of the rotor core 32A near an axial end side of the permanent magnet 32B on the outer peripheral surface of the rotor core 32A. An adhesive for fixing the permanent magnet 32B to the rotor core 32A is coated on the circumferential groove 32C and the axial end face of the permanent magnet 32B. COPYRIGHT: (C)2005,JPO&NCIPI

Condition monitoring of wind generators

Abstract: This paper focuses on the experimental investigation for incipient fault detection and fault detection methods existing in the literature suitably adapted for use in wind generator systems using doubly fed induction generators (DFIGs) Three main experiments (one for stator phase unbalance, one for rotor phase unbalance and one for turn-to-turn faults) have been performed to study the electrical behaviour of the DFIG The article aims to provide wind generators with further documentation for an advanced condition monitoring system, in order to avoid undesirable operating conditions and to detect and diagnose incipient electrical faults

Terminal voltage control of a wind turbine driven isolated induction generator using stator oriented field control

Abstract: This paper presents the voltage build up process and terminal voltage control in an isolated wind powered induction generator driven by a variable speed wind turbine using stator flux oriented vector control. Here three-phase induction generator is excited using a PWM inverter/rectifier connected to a single capacitor on the DC side. Wind powered isolated induction generators have an input, wind, which is not controllable, but they can be set to operate within a given variation of speed. Unlike a grid connected induction generator, in an isolated induction generator there should be a control system that keeps the DC bus voltage at a constant value when the speed of the rotor is varied. This paper present the control system to maintain the DC bus voltage at a constant value by varying the flux in the induction generator when the rotor speed is varied. During voltage build up the variation of magnetizing inductance is taken into consideration.

Design, Analysis and Hover Performance of a Rotary Wing Micro Air Vehicle

Abstract: An initial design concept for a micro-coaxial rotorcraft using custom manufacturing techniques and commercial off-the-shelf components is discussed in this paper. Issues associated with the feasibility of achieving hover and fully functional flight control at small scale for a coaxial rotor configuration are addressed. Results from this initial feasibility study suggest that it is possible to develop a small scale coaxial micro rotorcraft weighing approximately 100 grams, and that available moments are appropriate for roll, yaw and lateral control. A prototype vehicle was built and its rotors were tested in a custom hover stand used to measure Thrust and power. The radio controlled vehicle was flown untethered with its own power source and exhibited good flight stability and control dynamics. The best achievable rotor performance was measured to be 42%.

A sensorless initial rotor position estimation scheme for a direct torque controlled interior permanent magnet synchronous motor drive

Abstract: In direct torque control (DTC) scheme, the requirement of the continuous rotor position sensor and coordinate transformation is eliminated since all the calculation is done in stator reference frame. However, the DTC scheme requires the position sensor to determine the initial position of the rotor at starting. Elimination of the shaft-mounted position encoder is a very desirable objective in many applications since this sensor is often one of the most expensive and fragile components in the entire drive system. This paper presents a sensorless method of determining the initial rotor position of a direct torque controlled interior permanent magnet (IPM) synchronous motor drive. The method consists of injecting a high frequency voltage to the windings and examining the effects of the saliency on the amplitude of the corresponding stator current components. This method does not depend on the level of static load and on any motor parameters. The magnet polarity of the rotor at its initial position is also identified using the effect of saliency. Modeling and experimental results verify the effectiveness of the proposed method.

Segmental rotor switched reluctance motors with single-tooth windings

Abstract: Switched reluctance machines with segmental rotors are investigated, building on previous work which has produced high torque prototypes. The paper presents a machine topology, which permits the use of short pitched windings placed around a single-tooth. This concept maintains the torque capability of a previous design, but uses much less copper volume. The theoretical basis for the machine configuration is developed and then the results for a working prototype machine are shown, illustrating static torque and flux linkage profiles. Results are presented for the machine operating as a drive, indicating the viability of the concept.

Rotation angle detector

Abstract: A rotation angle detector includes a rotor, first and second detecting elements which rotate according to a rotation of the rotor, first and second detecting units for detecting rotations of the first and second detecting elements, respectively, and a control unit for detecting a rotation angle of the rotor based on a first signal when a difference between the first and second signals output from the first and second detecting units ranges within a predetermined range. The rotation angle detector has a simple structure and detects the rotation angle of the rotor accurately

A novel detection method of motor broken rotor bars based on wavelet ridge

Abstract: Detection of cage motor broken rotor bars has long been an important but difficult job in the detection area of motor faults. The characteristic frequency component of faulted rotor (CFCFR) is very close to the power frequency component but by far less in amplitude, which brings about great difficulty for accurate detection. A new detection method based on wavelet ridge is presented in this paper. Aiming at the motor's starting period during which the motor accelerates progressively and CFCFR approaches the power frequency gradually in frequency spectrum, the wavelet ridge-based method is adopted to analyze this transient procedure and the CFCFR is extracted. The influence of power frequency can be effectively eliminated, and detection accuracy can be greatly improved by using the approach presented in this paper. Also, this is indeed a novel but excellent approach for the detection domain of cage induction motor broken rotor bars.

Numerical Implications of Solidity and Blade Number on Rotor Performance of Horizontal-Axis Wind Turbines

Abstract: A numerical study was conducted to examine the impact of rotor solidity and blade number on the aerodynamic performance of small wind turbines. Blade element momentum theory and lifting line based wake theory were utilized to parametrically assess the effects of blade number and solidity on rotor performance. Increasing the solidity beyond what is traditionally used for electric generating wind turbines led to increased power coefficients at lower tip speed ratios, with an optimum between 3 and 4. An increase in the blade number at a given solidity also increased the maximum C p for all cases examined. The possibility of a higher aerodynamic power extraction from solidity or blade number increases could lead to a higher overall system power production. Additional advantages over current 5% to 7% solidity, high speed designs would include lower noise, lower cut-in wind speed, and less blade erosion.

Oil free screw compressor

Abstract: A screw compressor includes a compressor main body, a male rotor having a screw-like male tooth shape and a female rotor having a screw-like female tooth shape meshing with the screw-like male tooth shape or the male rotor. The male and female motors are provided within the compressor main body. A motor casing is operably connected to the compressor main body, and a high speed electric motor provided within the motor casing. The motor includes a motor rotor, a motor stator and a motor shaft for driving at least one of the male and female rotors. A speed ratio of the motor shaft and the at least one of the male and female rotors driven by the motor shaft is in a range of 2:1 to 1:2.