Showing papers on "Rotor (electric) published in 1995"

Transient analysis of cage induction machines under stator, rotor bar and end ring faults

Abstract: An analysis method is developed for modeling of multi phase cage induction motors with asymmetry in the stator, arising due to an interturn fault resulting in a disconnection of one or more coils making up a portion of a stator phase winding and any distribution and number of rotor bar and end-ring failures. The approach, based on the winding functions, makes no assumption as to the necessity for sinusoidal MMF and therefore include all the space harmonics in the machine. Simulation and experimental results confirm the validity of the proposed method. >

Modeling of a piezoelectric rotary ultrasonic motor

Abstract: A piezoelectric rotary ultrasonic motor is modeled for the purpose of predicting, a priori, motor performance as a function of design parameters. The Rayleigh-Ritz assumed mode energy method is used to model the distributed piezoceramics and the traveling wave dynamics of the stator. Natural frequencies and modeshapes are obtained for a generally configured motor. Nonlinear normal and tangential interface forces between the rotor and stator are incorporated into the forcing function along with the linear piezoelectric forcing. Given the applied torque, applied axial loading, and piezo drive voltages as inputs to the model, general motor performance measures are obtained-namely speed, input power, output power, and efficiency. The approach presented here provides a general framework for modeling these motors as well as a design tool for optimizing prototypes with the added flexibility of allowing for a wide variety of geometries and materials. >

Modeling of motor bearing currents in PWM inverter drives

Abstract: Pulse-width modulated (PWM) inverters have recently been found to be a major cause of motor bearing failures in inverter-fed motor drive systems. Specifically, all inverters generate common-mode voltages relative to the earth ground. These voltages provide coupling or bearing currents through motor parasitic capacitances to the rotor iron which flow via the bearings to the grounded stator case. In this paper, a model of bearing currents caused by PWM inverters is proposed. The model is based on transmission line theory which uses an equivalent lumped parameter /spl pi/-network to describe the parasitic coupling phenomenon. The model parameters are then identified by matching the calculated model outputs with those of experimental measurement. The validation of the method is demonstrated by the fact that the model can reproduce a variety of experimental results obtained on a test motor. An application of this method also gives a motor grounding current model. As the conducted electromagnetic interference (EMI) in motor drive systems is related to the grounding currents, the grounding current model can be used for the analysis of conducted EMI in motor-drive systems.

Fabrication and characterization of PZT thin-film vibrators for micromotors

Abstract: For the first time we have characterized a micromotor driven by a piezoelectric PZT (PbZrxTi1-xO3) thin film. Sputter and sol-gel techniques have been applied for the deposition of the PZT films onto a silicon stator membrane, which is 20-30 mu m thick and has a diameter of 4 mm. The amplitudes of the membrane deflections are measured by means of laser interferometry. They are as large as 800 nm V-1 at the first resonance (26 kHz) and 60 nm V-1 at 1 kHz. This is one order of magnitude larger than previously reported for a ZnO-activated device of similar geometry. The motor operates at 1-3 V-r.m.s., with speeds of up to 200 rpm at 1.1 V-r.m.s. and torques of 35 nN m at 2.5 V-r.m.s. and 1 mN force between rotor and stator. Compared with the conceptually identical ZnO version published by Racine et al., this is an improvement by a factor of three in speed per volt. Taking into account the linear increase of the torque with the stator vibration frequency, the torque per volt is a factor of two higher. A long-term test of 100 h showed no degradation of the motor performance.

Theory and optimum design of PM Vernier motor

Abstract: The paper introduces a novel motor, known as the PM Vernier motor, which produce high torques at very low speed and can be used for direct drive applications. After a description of its construction and principle of high torque generation at very low speed, a design method is shown which can optimize the motor torque. The torque measured for a motor made on an experimental basis showed a high torque per rotor unit volume of 112 kNm/m/sup 3/ from a current of 8 A and agreed well with calculated values. A block diagram of a speed control scheme and an example of measured speed response characteristics are also shown.

Disk storage drive

Abstract: A disk storage has one or more disks provided with center holes. An electric motor extends coaxially through these holes and has an external rotor to the outer circumference of which the disks are secured so that they rotate with the rotor. A seal is provided for at least reducing the escape of contaminants from the motor.

Chaotic responses of unbalanced rotor/bearing/stator systems with looseness or rubs

Abstract: The first part of this paper presents results of numerical simulation of the dynamic behavior of a one-lateral-mode unbalanced and radially side-loaded rotor with either a loose pedestal (looseness in a stationary joint), or with occasional rotor-to-stator rubbing. The nonlinearities of these systems (variable stiffness, impacting, and friction) are associated with the rotor intermittent contacts with the stationary element. The results, based on a newly developed local impact model [P. Goldman and A. Muszynska, Analytical and experimental simulation of loose pedestal dynamic effects on a rotating machine vibrational response, Rotating Machinery Dynamics, DE-Vol. 35, ASME, Miami, Florida, pp. 11–17 (1991); P. Goldman and A. Muszynska, Analytical model of the impact between rotating and nonrotating elements and its application in rotor-to-stator rubbing, BRDRC Report 1, (1992); P. Goldman and A. Muszynska, Chaotic behavior of rotor-to-stator systems with rubs, ASME Turbo EXPO Conference, 93-GT-34, Cincinnati, Ohio, Transactions of the ASME (to appear); P. Goldman and A. Muszynska, Dynamic effects in mechanical structures with gap and impacting: Order and chaos, Trans. of ASME, J. Vibration and Acoustics (1994)] exhibit regular periodic vibrations of synchronous (1×) and subsynchronous ( 1 2 ×, 1 3 × , …) orders, as well as chaotic vibration patterns of the rotor, all accompanied by higher harmonics. The second part of the paper presents experimental vibration characteristics of rotors with looseness or rubs, obtained from rotor rigs. The results display similar patterns as those obtained analytically.

High performance PMSM drives without rotational position sensors using reduced order observer

Abstract: A new position sensor elimination method for high performance permanent magnet synchronous motor (PMSM) drives is presented in this paper. The back-EMF quantity of the PMSM has mechanical information such as the rotor speed and angle in itself. Therefore, without exterior rotational sensors or other mechanical data which include machine inertia, viscous friction, and outer load condition, these essential information for proper PMSM drives can be obtained successfully from only the back-EMF quantity. In this study, with the help of the modern state observer technique for back-EMF estimation, the rotor position as well as the machine speed are estimated strictly and utilized for practical sensorless PMSM drives. Furthermore, introducing the 'angle ambiguity compensation' algorithm, the proposed sensorless scheme has good starting ability and high performance driving characteristics even in the transient state, such as speed fluctuation or speed reversal. In order to verify the feasibility of the proposed method, extensive experimental results are presented under full operating conditions, 150/spl sim/2500 [RPM] speed and 0/spl sim/1 [p.u.] load range.

Mechanical thrombus maceration device

Abstract: In one embodiment, the present invention provides a mechanical thrombus maceration device which includes a flexible shaft adapted to be guided along a vascular path and rotated within a vascular channel; a rotor affixed to the shaft adjacent the distal end thereof for rotation therewith; drive means for rotating the shaft; and a rotor housing within which the rotor rotates. The rotor housing of this embodiment comprises a generally cylindrical wall substantially surrounding the rotor and having at least one port formed therein, the port or ports being positioned about the housing such that when a fluid (e.g. blood) is ejected through the ports within a vascular channel, the housing will tend to deflect toward one side of the vascular channel to permit the device to be steered during deployment. In another embodiment of the invention, the device includes an elongate, flexible shaft adapted to be guided along a vascular path and which is rotatable within a vascular channel; a plurality of rotors spaced from one another along the shaft and attached to the shaft for rotation therewith; drive means for rotating the shaft; and a rotor housing enclosing at least one of the rotors.

Downflow spin dryer

Abstract: A downflow spin dryer, includes a housing; a rotor rotating within the housing in a direction of rotation, the rotor including first and second opposite mounting holes at different heights; a cradle fitted within the rotor for accommodating semiconductor substrates to be dried, the cradle having a rear portion and a front portion as viewed with respect to the direction of rotation of the rotor, the cradle being fitted to the rotor such that the rear portion of the cradle is at a lower position than the front portion of the cradle, the cradle including first and second opposite mounting holes in alignment with the first and second mounting holes, respectively, of the rotor when the cradle is fitted within the rotor, the first and second mounting holes of the cradle being at the same height; screws for entering the first mounting holes of the cradle and the rotor, and for entering the second mounting holes of the cradle and the rotor, so as to mount the cradle within the rotor; an air inlet in an upper surface of the housing above the rotor through which air is sucked along with the rotation of the rotor; an air outlet in the housing through which air sucked through the air inlet is discharged; and a filter over the air inlet to prevent incursion of dust into the dryer.

Horizontal axis wind turbine

Abstract: A horizontal axis wind turbine comprises a rotor-supporting framework, a multi-vaned rotor, an electricity-generating stator, and a rotation track. The supporting framework is constructed with a plurality of triangular sub-units. The rotor has a plurality of vanes projecting therefrom. The vanes have adjustable pitch and are encircled by a rim having a plurality of magnets. Wind induces rotation of the rim. The stator is essentially stationary and is mounted on the framework opposite the rim. As magnets on the rotating rim pass by the stator, electricity is generated. The stator uses the pull of the magnets to automatically adjust itself to align with the rotating rim. The framework is mounted on the rotation track so that the framework can continually be adjusted to maximize wind-induced rotation of the rotor.

Fluid micropumps based on rotary magnetic actuators

Abstract: A jet-type magnetically driven fluid micropump to drive conductive fluids has been designed, fabricated, and tested The pump actuation is based on a rotary magnetic micromotor with fully integrated stator and coils operating with the rotor immersed in the fluid to be pumped, thereby driving the fluid from a inlet flow reservoir through integrated flow channels to an outlet flow reservoir The micropump has been successfully driven using standard diabetic-prescription insulin in saline buffer (Novo Nordisk, Regular Insulin) as a working fluid, demonstrating the feasibility of a rotary micropump for pumping and injecting fluids in drug delivery or chemical flow systems The attained flow rate varies monotonically with motor speed In the realized micropump, the fluid flow rate achieved is up to 24 p!/min at a rotor speed of 5000 rpm The operating voltage is less than 3 V and the power consbmption is approximately 05 W The differential pressure is expected to be approximately 100 hPa

Remote self-powered structure monitor

Abstract: An acoustic rotor monitor that is an autonomous self-powered measurement instrument which can detect embedded and hidden fatigue cracks in remotely inaccessible devices such as helicopter rotor system components. A predictive maintenance-related problem for rotor craft is the detection of fatigue cracks as a continuous real-time monitoring process under dynamic rotor system loading conditions. The rotor monitor focuses on the embedding an acoustic emission-based smart sensor directly into the rotor system to measure the high frequency stress waves indicating that a structural crack has propagated as a "self-powered" measurement without reducing structural integrity.

Magnetorheological fluid devices and process of controlling force in exercise equipment utilizing same

Abstract: The invention relates to magnetorheological (MR) fluid devices (20) and the process of controlling the force in exercise equipment by utilizing the MR fluid devices. The MR fluid devices include rotary and linear acting varieties and are useful for controlled forces in exercise bicycles, recumbent exercisers, ski machines, rowing machines, and stair stepper machines. The rotary MR fluid device is comprised of a rotor (26) supported by bearings (44) and received within a housing (22). An MR fluid is received adjacent the rotor (26) and within a cavity (28) in the housing (22) and the MR fluid is controlled by an applied magnetic field to vary the operating torque resistance. Spring (43) biasing the rotor (26) allows for relaxed tolerances. Optimization of the Ri/Ro ratio is described which reduces the size and weight of the device (20). The linear acting version utilizes simple extensible pumps and an external MR fluid valve to provide a modularized system.

Rotor cage fault diagnosis in three-phase induction motors, by Park's vector approach

Abstract: The subject of on-line detection of rotor cage faults in three-phase induction motors is discussed, and a noninvasive approach, based on computer-aided monitoring of the stator current Park's vector, is introduced, Both simulation and laboratory test results demonstrate the effectiveness of the proposed technique, for detecting broken rotor bars or end-rings in operating three-phase induction machines. On-site tests conducted in a power plant, using the diagnostic instrumentation system developed, are also reported.

Compressor rotor cooling system for a gas turbine

Abstract: In a gas turbine including a compressor having a bore and a rotor comprised of multiple stages extending between a first stage at a forward end of the compressor and a last stage at an aft end of the compressor, each stage including a rotor disk having a peripheral rim and multiple blades secured to the peripheral rim, a combustion system comprising a plurality of combustors utilizing discharge air from the compressor for combustion, and multiple turbine stages driven by combustion gases from the combustion system, the improvement comprising means for supplying cooling air at least to a peripheral rim of the last stage of the compressor.

Design of a traveling wave type ultrasonic motor

Abstract: The purpose of the present paper is to establish a method of design for a traveling wave type ultrasonic motor. This method is based on two models for the ultrasonic motor. A two-dimensional elastic contact model is used for estimating the friction drive between the rotor and vibrator of the motor. Moreover, an electrical equivalent circuit is used to estimate the interaction between the electrical and mechanical parts of the vibrator. The proposed method is applied to the design of a prototype motor. To determine applicability of the method, the load characteristics of the prototype motor are measured. The measured characteristics agree with the required ones which are specified in advance. As a result, the validity of the proposed method is experimentally confirmed. >

Detection of starting motor position in a brushless DC motor

Abstract: A microprocessor-controlled-circuit applies pulses to a standing motor whose rotor position is to be determined. The time required for the injected current to reach a predetermined threshold in a comparator is measured. The pulses are long enough to effectuate an accurate measurement, but not so long that the rotor moves. The pulse is applied twice to each phase, once with a positive polarity and once with a negative polarity, for a total of six measurements. The positive and negative rise times are subtracted from each other to determine whether the positive or negative current rise time was greater. Based upon the differences in the readings for all of the phases, the position of the rotor is known. There are differences in which the difference is zero or negligible. There are at least two methods to determine rotor position when there are ambiguities in the sign of the difference. In one method, the combination of the sign of the rise time difference or its absence plus the magnitude of the rise time can be used along with look-up tables to determine the rotor position. Another method is to resolve a position uncertainty by changing the effective rotor position. This is done by pulsing all three phases actively. Instead of leaving a phase open during pulsing, the third phase is tied high or is tied low. Once start-up ambiguities are resolved, control of acceleration from stand-still through medium speed to constant, nominal speed is provided.

Reaction force generating apparatus

Abstract: A reaction force generating apparatus is provided which generates a reaction force for a rotationally operated member to be manually or mechanically operated. An alternating motor is provided that has a stator with three-phase coils; a rotor including permanent magnets; and a rotational axle extending from the center of the rotor and having a rotationally operated member attached to its one end. A direct voltage is supplied to the three-phase coils of the alternating motor, thereby producing a magnetic field on the stator. The magnetic field is oriented in one direction and cooperates with the permanent magnets to generate an electromagnetic attraction force for maintaining the operated member in a predetermined angular position. When the operated member is moved, a torque, or reaction force, is generated to restore the initial position of the operated member.

Voltage dependent reactive power limits for voltage stability studies

Abstract: This paper presents and studies a static model for synchronous generators with voltage dependent reactive power limits due to maximum stator current, maximum and minimum rotor (field) current as well as maximum rotor angle (underexcitation) limiters. The proposed generator model for static voltage stability studies can be included in an ordinary power flow program, and results from studies on a test system with twenty generators are presented. The influence of voltage dependent reactive power limits is compared with fixed (conventional) limits, by use of the minimum singular value of the power flow Jacobian matrix and related submatrices as indicators of the static voltage stability limit. >

Gas turbine rotor blade tip cooling device

Abstract: A gas turbine hollow cooled rotor blade in which a plurality of cooling holes (3 and 5) are provided which communicate between a cooling air passage in the blade and the tip squealer portion (1) on the pressure side and between the cooling air passage in the blade and a position in the vicinity of the suction side of a tip cap (4).

Variable-frequency synchronous motor drives for electric vehicles

Abstract: The performance capability envelope of a variable-frequency, permanent-magnet synchronous motor drive with field weakening is dependent upon the product of maximum current and direct-axis inductance. To obtain a performance characteristic suitable for a typical electric vehicle drive, in which short-term increase of current is applied, it is necessary to design an optimum value of direct-axis inductance. The paper presents an analysis of a hybrid motor design which uses a two-part rotor construction comprising a surface-magnet part and an axially laminated reluctance part. This arrangement combines the properties of all other types of synchronous motor and offers a greater choice of design variables. It is shown that the desired form of performance may be achieved when the high-inductance axis of the reluctance part is arranged to lead the magnet axis by 90/spl deg/ (elec.).

Multi degree of freedom spherical ultrasonic motor

Abstract: This paper presents a multidegree of freedom spherical ultrasonic motor. As a prototypical spherical ultrasonic motor, we have successfully developed two kinds of spherical ultrasonic motor with two degree of freedom. Each type has good controllability; the motor can drive a spherical rotor about an arbitrary axis; the maximum speed is 30 rpm; the maximum output torque is 0.7 kg cm; the maximum positioning error is 0.3 mm. It is expected to be applied to not only robotic manipulator's actuator but also assembling machine, laser cutting and many fields.

Analysis and comparison of PM synchronous motor and induction motor type magnetic bearings

Abstract: In this paper, a general solution of radial position control applicable to PM synchronous type and induction type rotating motors is presented. The rotor of the permanent magnet motor is assumed to have sinusoidally distributed magnetic poles along the axial surface, while the rotor of the induction type motor is assumed to have uniform magnetic property. The inner wall of the stator is also assumed to have a current sheet, which can produce an arbitrary current distribution. The same number of magnetic poles gives the rotating torque to the rotor, while plus/minus two poles of the motoring control produces a pure radial force to the rotor. By controlling the magnitude and phase of the plus/minus two-pole current distribution relative to the motoring magnetic pole, the radial force can be controlled in the radial coordinate. This general solution is experimentally confirmed by using a simple experimental setup. >

Navier-Stokes calculations of rotor-airframe interaction in forward flight

Abstract: A method for analyzing the mutual aerodynamic interaction between a rotor and an airframe model has been developed. This technique models the rotor implicitly through the source terms of the momentum equations. A three-dimensional, incompressible, laminar, Navier-Stokes solver in cylindrical coordinates was developed for analyzing the rotor-airframe problem. The calculations are performed on a simplified rotor-airframe model at an advance ratio of 0.1. The airframe surface pressure predictions are found to be in good agreement with wind tunnel test data. Results are also presented for velocity and pressure field distributions in the wake of the rotor.

Rotating electrical machine with electromagnetic and permanent magnet excitation

Abstract: In several embodiments of the present invention, an alternator is disclosed. The alternator includes a rotor having both wound-field and permanent magnet poles. The wound-field and permanent magnet poles are disposed about the circumference of the rotor.

Robust adaptive control of flexible joint robots with joint torque feedback

Abstract: This paper addresses motion control issues of flexible joint robot manipulators using joint torque feedback. A two-stage control scheme consisting of a motion controller and a joint torque controller is established in a systematic way for the general n-link case. To deal with uncertainties in the robotic system, a robust adaptive control algorithm is developed assuming that all system parameters including the joint flexibility values are unknown except for some of their bounds. The system stability is analyzed via Lyapunov stability theory. The result has the distinct feature that no restriction of joint flexibility, nor exact knowledge of the parameters of rotor subsystem is required. The outcome is a useful framework for generalization of control methods previously developed for rigid robots. Simulation results verify the effectiveness of the proposed control methods.