Showing papers on "Rotational speed published in 2007"

Modeling of the Wind Turbine with a Permanent Magnet Synchronous Generator for Integration

Abstract: The paper presents the dynamic model and control schemes of a variable speed pitch wind turbine with permanent magnet synchronous generator (PMSG). The model includes a PMSG model, a pitch-angled controlled wind turbine model and a drive train model. The drive train model uses one-mass model to represent the mechanical characteristics of the generator set. The generator model is established in the dq-synchronous rotating reference frame. The wind turbine model details the mechanism of variable speed operation of the turbine by a pitch control. The control schemes in the paper include a pitch angle control for the wind turbine and a speed control for the generator. The pitch angle control uses wind speeds and electric power output as the input signals to ensure normal operation in high wind speed. The speed control is realized through field orientation where the d-axis current is set to zero and the q-axis current is used to control the rotational speed of the generator according to the variation of wind speed. In order to verify the presented model and the control strategy, simulations with MATLAB/Simulink software have been conducted. Simulation results prove the validity of the model and the control schemes.

Power tool anti-kickback system with rotational rate sensor

Abstract: A control system is provided for use in a power tool The control system includes: a rotational rate sensor having a resonating mass and a controller electrically connected to the rotational rate sensor The rotational rate sensor detects lateral displacement of the resonating mass and generates a signal indicative of the detected lateral displacement, such that the lateral displacement is directly proportional to a rotational speed at which the power tool rotates about an axis of the rotary shaft Based on the generated signal, the controller initiates a protective operation to avoid further undesirable rotation of the power tool The controller may opt to reduce the torque applied to shaft to a non-zero value that enables the operator to regain control of the tool

Variable valve timing apparatus

Abstract: In the case where an intake valve has its phase in a first region between a most retarded angle and CA(1), the rotational speed of relative rotation between an output shaft of an electric motor and a sprocket is reduced at a reduction gear ratio R(1) to change the phase of the intake valve. In the case where the intake valve has its phase in a second region between CA(2) and a most advanced angle, the rotational speed of relative rotation is reduced at a reduction gear ratio R(2) to change the phase of the intake valve. As long as the rotational direction of relative rotation is the same, the phase of the intake valve is changed in the same direction for both of the first region between the most retarded angle and CA(1) and the second region between CA(2) and the most advanced angle.

Experimental study on rheologic behaviour of debris flow material

Abstract: In order to describe the flow behaviour of debris flows often rheologic models are used. This study introduces two novel facilities to determine rheologic parameters of different models for debris flow material mixtures containing grain sizes larger than to be measured in standard viscometers. The diameter of the vertically rotating flume (VRF) is 2.5 m, the rectangular cross section has a width of 0.45 m, and the maximum rotational speed is around 30 revolutions per minute, corresponding to a mean speed of the examined mixture of ∼4 m/s. From the measured flow parameters total boundary shear stress and corresponding shear rate of the flowing mixture are derived. The ball measuring system (BMS) consists of a sphere that is dragged at specific speeds across a sample of 0.5 l volume with the help of a small sphere holder. Accordingly torques due to drag exerted on the sphere and its holder as well as corresponding speeds are measured and transformed into values of shear stress and shear rate based on the method of Metzner and Otto. Material taken from fresh debris flow deposits in Eastern Switzerland have been investigated with both facilities. We present results from experiments involving mixtures with different sediment concentrations and with grain sizes up to 5 mm. Although estimated from completely different approaches the rheologic parameters of the independent measurements are generally in reasonable agreement.

Power output apparatus, vehicle equipped with power output apparatus, and control method of power output apparatus

Abstract: When a required speed ratio as a required value of a speed ratio between an engine and a driveshaft becomes equal to or less than a lower limit speed ratio that is not more than an n-th shift speed ratio during an n-th speed state of a transmission, a hybrid vehicle controls the engine, two motors, and the transmission to ensure output of power based on a torque demand to the driveshaft while performing an engine rotational speed adjustment of making a rotational speed of the engine equal to a shift rotational speed corresponding to an upper side shift speed ratio or an effective shift speed ratio and a shift from an n-th speed state to an (n+1)-th speed state.

High to low pressure spool summing gearbox for accessory power extraction and electric start

Abstract: A turbine engine includes low and high pressure spools. A high power take-off shaft is coupled to the high spool. An auxiliary component, such as a generator, is configured to be driven by the high power take-off shaft at a first speed. The low spool, in part, drives the auxiliary component, for example, by interconnecting the high power take-off shaft to a lower power take-off shaft through a speed summing gearbox. The gearbox drives the auxiliary component and increases the rotational speed of the auxiliary component from the first speed to the second speed. The low power take-off shaft also drives another generator, in one example. The turbine engine can be started by the low pressure generator, for example, in response to a command from a controller, which transforms the generator into a starter motor.

Hybrid vehicle control apparatus

Abstract: A hybrid vehicle control apparatus is provided with a motor/generator arranged between an engine and a transmission, a first clutch disposed between the engine and the motor/generator, a second clutch disposed in a power train spanning from the motor/generator to a drive wheel, and a controller. The controller controls the engagement of the first and second clutches to select either an electric drive mode or a hybrid drive mode. The controller executes a rotational speed control of the motor/generator while in a coasting state with torque being transmitted through a one-way clutch of the transmission such that the rotational speed control increases an input rotational speed of the one-way clutch to a value closer to an output rotational speed of the one-way clutch with a difference between the input and output rotational speeds of the one-way clutch becoming equal to a target value.

Drive state shift control apparatus and method for vehicle

Abstract: A drive state shift control apparatus and method switches a hybrid drive (HEV) mode to an electric drive (EV) mode without engine stoppage shock or eliminates gearshifting shock in an electric vehicle In response to a decrease in accelerator opening APO, a request for fourth-to-fifth upshift is issued, then request for HEV-to-EV mode shift is issued At the time of the upshift, a direct clutch D/C is disengaged At a first time interval after the mode shift is issued, a first clutch is disengaged At a second time interval after the mode shift is issued, the engine begins to stop and the rotational speed of the motor-generator is controlled so that the speed falls to a predetermined rotational speed close to an after-gearshift rotational speed within a target shifting time interval When the rotational speed reaches the predetermined rotational speed, a front brake Fr/B is engaged to perform a fourth-to-fifth upshift, and the torque of the motor is controlled so as to engage the one-way clutch smoothly

Effect of welding parameters on the strain rate and microstructure of friction stir spot welded 2024 aluminum alloy

Abstract: The stir zone microstructure, crystallographic texture, temperature and strain rate in the stir zones produced during Al 2024 spot welding using different tool rotational speed settings are investigated. The calculated strain rate during spot welding decreases from 1600 to 0.6 s−1 when the tool rotational speed increases from 750 to 3000 rpm. The low strain rate values are associated with tool slippage resulting from spontaneous melting of S phase particles at temperatures ≥490 °C. However, the calculated strain rate is 1600 s−1 in Al 2024 spot welds made using tool rotational speed of 750 rpm since the temperature never reaches 490 °C. Material transfers downwards via that pin thread during the dwell period in Al 2024 spot welding. It is proposed that this downward transfer of material provides a continuous supply of undissolved S phase particles, which melt spontaneously when the welding parameter settings produce stir zone temperatures ≥490 °C. A weak crystallographic texture where the {100} planes are oriented at about 45° to the θ-direction exists in the stir zones of spot welds made using different tool rotational speeds (from 750 to 3000 rpm). Another crystallographic texture where the {100} planes are parallel to the Z-direction (to the tool axis) is stronger in spot welds made using higher tool rotational speed settings. Also, material located at the root of the pin thread has a quite different crystallographic texture from that in the bulk of the stir zone.

Analysis of counter-rotating wind turbines

Abstract: This paper presents a study on the performance of a wind turbine with two counter- rotating (CRWT) rotors. The characteristics of the two counter-rotating rotors are on a 3- bladed Nordtank 500 kW rotor. The analysis has been carried out by using an Actuator Line technique implemented in the Navier-Stokes code EllipSys3D. The analysis shows that the Annual Energy Production can be increased to about 43.5 %, as compared to a wind turbine with a single rotor. In order to determine the optimal settings of the CRWT turbine, parameters such as distance between two rotors and rotational speed have been studied.

Contact analysis of a flexible bladed-rotor

Abstract: This paper presents a model of fully flexible bladed rotor developed in the rotating frame. An energetic method is used to obtain the matrix equations of the dynamic behaviour of the system. The gyroscopic effects as well as the spin softening effects and the centrifugal stiffening effects, taken into account through a pre-stressed potential, are included in the model. In the rotating frame, the eigenvalues' imaginary parts of the latter matrix equation give the Campbell diagram of the system and its stability can be analysed through its associated eigenvalues' real parts. The turbo machine casing is also modelled by an elastic ring in the rotating frame through an energetic method. Thus, in some rotational speed ranges the contact problem between the rotor and the stator can be treated as a static problem since both structures are stationary to each other. Prior to the study of the complete problem of contact between the flexible blades of the rotor and the flexible casing, a simple model of an elastic ring having only one mode shape, excited by rotating loads is developed in the rotating frame too, in order to underline divergence instabilities and mode couplings. Then, the complete problem of frictionless sliding contact between the blades and the casing, without rubbing, is studied. The stable balanced static contact configurations of the structure are found as function of the rotational speed of the rotor. Finally, the results are compared to these of the simple model of rotating spring-masses on an elastic ring, showing good adequacy. The present model of rotor appears thus particularly adapted to the study of blades-casing contacts and highlighted an unstable phenomenon near the stator critical speed even in case of frictionless sliding.

Double-clutch transmission

Abstract: In a double-clutch transmission, a clutch of an input shaft which is not synchronously rotated with a output shaft is connected to synchronize the speed of rotation of the input shaft with that of the engine, and the rotational speed of the input shaft is measured to thereby detect a engine rotational speed.

Performance test and flow measurement of contra-rotating axial flow pump

Abstract: An application of contra-rotating rotors has been proposed against a demand for developing higher specific speed axial flow pump. In the present paper, the advantage and disadvantage of using contra-rotating rotors are described in comparison with conventional type of rotor-stator, based on theoretical and experimental investigations. The advantages are as follows: (1) The pump is inherently designed as smaller sized and at lower rotational speed. (2) A stable head-characteristic curve for flow rate with negative slope appears. (3) As the rear rotor rotational speed is varied as independent control of front rotor, the wider range of high performance operation is obtained by rear rotor speed control in addition to front rotor speed control. The disadvantages are as follows: (1) The structure of double shaft system becomes complex. (2) The pump performance is inferior at over flow rate as the rear rotor loading is weakened. (3) The blade rows interaction from rear rotor to front rotor more strongly appears. Then the rear rotor design is a key to achieve higher pump performance. Some methods to overcome these disadvantages will be discussed in more details toward wider usage of contra-rotating axial flow pump in various industrial fields.

Stability-Based Spindle Design Optimization

Abstract: Prediction of stable cutting regions is a critical requirement for high-speed milling operations. These predictions are generally made using frequency-response measurements of the tool-holder-spindle set obtained from a nonrotating spindle. However, significant changes in system dynamics occur during high-speed rotation. In this paper, a dynamic high-speed spindle-bearing system model is elaborated on the basis of rotor dynamics prediction and readjusted on the basis of experimental modal identification. The dependency of dynamic behavior on speed range is then investigated and determined with accuracy. Dedicated experiments are carried out in order to confirm model results. They show that dynamic effects due to high rotational speed and elastic deformations, such as gyroscopic coupling and spin softening, have a significant influence on spindle behavior. By integrating the modeled speed-dependent spindle transfer function in the chatter vibration stability approach ofAltintas and Budak (1995, CIRPS Ann, 44(1), pp. 357-362), a new dynamic stability lobe diagram is predicted. Significant changes are observed in the stability limits constructed using the proposed approach and allow accurate prediction of cutting conditions to be established. Finally, optimization studies are performed on spindle design parameters in order to obtain a chatter vibration-free cutting operation at the desired speed and depth of cut for a given cutter.

Rotary electric machine

Abstract: PROBLEM TO BE SOLVED: To reduce rotational resistance resulting from churning of lubricating oil at the time of high speed rotation, by controlling feed of the lubricating oil to a slot of a rotary electric machine. SOLUTION: A screen member 90 is arranged at a rotor end face 18a of rotary electric machine 10. Responding to an increase in rotational speed of rotor 18, the screen member 90 moves outward in a radial direction of the axis of a rotary shaft 12, so that part of opening 86 of a slot 82 is covered. Feed of the lubricating oil into the slot 82 from the exterior in an axial direction of rotary shaft 12 through the rotor end face 18a is restricted by the screen member 90. During high-speed rotation of the rotor 18, rotational resistance of the rotor 18 resulting from churning of the lubricating oil can be reduced. COPYRIGHT: (C)2008,JPO&INPIT

Optimization design of rotor structure for high speed permanent magnet machines

Abstract: Permanent magnet (PM) machine is especially being employed in high speed machines due to its simple structure and high power density. Nowadays, the sintered neodymium-iron-boron (Nd-Fe-B) material is used in most of PM machines. This kind of PM material has large compression strength but small tensile strength, and can not withstand the large centrifugal force due to the high rotation speed. A nonmagnetic steel enclosure is needed to cover the PM material. The tensile press of PM can be reduced by pre-pressure applied to the outer surface of the PM through shrink-fitting into the enclosure. In this paper, the comprehensive optimization design of PM rotor structure is introduced with multiple constraints, such as deformation, stress and critical speed. The capacity of enclosure is the optimal goal. By finite element non-linear contact and optimization analysis, the optimized result for a high speed PM machine with rated speed of 60 000 rpm is presented.

Material behaviors and mechanical features in friction stir welding process

Abstract: This paper presents the 3D material flows and mechanical features under different process parameters by using the finite element method based on solid mechanics. Experimental results are also given to study the effect of process parameters on joining properties of the friction stir welds. Numerical results indicate that the tangent flow constitutes the major part in the material flow. The shoulder can accelerate the material flow on the top half of the friction stir weld. The distribution of the equivalent plastic strain can correlate well with the microstructure zones. Increasing the angular velocity of the pin, the material in the nugget zone can be more fully mixed, which improves the joining quality of the two welding plates. The increase of speeds, including the rotational speed and the translational speed, can both accelerate the material flow, especially in front of the pin on the retreating side where the fastest material flow occurs. The contact pressure on the pin-plate interface is decreased with the increase of the angular velocity.

Wind Turbine and Method for Determining at Least One Rotation Parameter of a Wind Turbine Rotor

Abstract: A method of determining at least one rotation parameter of a wind turbine rotor rotating with a rotation speed and a phase is provided. The method comprises the steps of: measuring an effective centrifugal force acting in a first pre-determined direction, which is defined in a co-ordinate system rotating synchronously with the rotor, on at least one reference object located in or at the rotor, establishing a first angular frequency representing the rotation speed of the rotor on the basis of variations in the measured effective centrifugal force due to gravitational force, establishing a second angular frequency representing the rotation speed of the rotor by use of at least one yaw rate gyro, and establishing the value of the rotation speed as the rotational parameter by correcting the second angular frequency by comparing it to the first angular frequency.

Development of a 2-Degree-of-Freedom Rotational/Linear Switched Reluctance Motor

Abstract: This paper presents a novel electromagnetic actuator having 2 degrees of freedom for rotational and linear actuation. It is based on a switched reluctance motor. Torque and thrust can be controlled independently. The prototype actuator is designed to perform 2-degree-of-freedom actuation with maximum rotational speed of 1000 min -1 and maximum thrust force of 30 N. In the motor performance testing, it has been confirmed that independently control of rotational speed and linear position is realized

Method and system for regulation of the rotational speed of a rotor on a wind turbine

Abstract: The invention relates to a method and a system for regulation of the rotational speed ( 52 ) of a rotor on a wind energy unit with a generator and a rotor blade. The first set parameter is a pitch angle (Pitch) of the rotor blade and the second set parameter is the torque of the generator. The system comprises a pitch angle control or regulation device ( 32 ), a torque control or regulation device ( 33 ), a first device for determination of a first rotational speed set value ( 28 ) (first rotational speed set value determination device ( 29 )) and a second device ( 26 ) for determination of a second rotational speed set value ( 29 ) (second rotational speed set value determination device ( 26 )). The first rotational speed set value ( 28 ) may be supplied to the pitch angle control or regulation device ( 32 ) and the second rotational speed set value ( 29 ) may be supplied to the torque control or regulation device ( 33 ), wherein the first and second rotational speed set value ( 28, 2 )) may be different from each other.

Method for preparing silicon carbide single crystal

Abstract: A SiC single crystal is produced by the solution growth method in which a seed crystal attached to a seed shaft is immersed in a solution of SiC dissolved in a melt of Si or a Si alloy and a SiC single crystal is allowed to grow on the seed crystal by gradually cooling the solution or by providing a temperature gradient therein. To this method, accelerated rotation of a crucible is applied by repeatedly accelerating to a prescribed rotational speed and holding at that speed and decelerating to a lower rotational speed or a 0 rotational speed. The rotational direction of the crucible may be reversed each acceleration. The seed shaft may also be rotated synchronously with the rotation of the crucible in the same or opposite rotational as the crucible. A large, good quality single crystal having no inclusions are produced with a high crystal growth rate.

Slip ratio estimating device and slip ratio control device

Abstract: A slip ratio estimating device for measuring the slip ratio without using the speed of a vehicle body and a slip ratio control device using the slip ratio estimating device are provided. A motor torque measured by a torque measurer is input into a vehicle model (601) and an SRE (602) which calculates the time derivative of the slip ratio. The vehicle model (601) derives the rotational speed of a wheel, the rotational acceleration of the wheel, and the speed of the vehicle body, and outputs the rotational speed of the wheel and the rotational acceleration of the wheel to the SRE (602). The SRE (602) outputs the slip ratio according to the motor torque, the rotational speed of the wheel, and the rotational acceleration of the wheel.