Abstract: A method and apparatus for detecting motor contamination utilizes zero-sequence currents in a sensing coil to detect contamination. The detector includes a current transformer comprised of a magnetic core and a sensing coil wound about the core. A processor processes a sub-trip level current from the sensing coil to detect contamination. Three contamination detection methods, which may be used separately or in desired combination, are based on current trends, current leakage, and current clustering. An alarm is triggered when predetermined alarm criteria have been met.

Abstract: An induction motor rotor comprises a rotor shaft (12), a rotor core (14), which may be solid (114) or may include a plurality of rotor laminations (13), having rotor bar slots (15), a plurality of rotor bars (16) extending through the rotor bar slots, and two rotor end rings (18) brazed to the rotor bars and extending to the rotor shaft, the rotor bars and rotor end rings pre-stressing the rotor core.

Abstract: A multipole brushless DC motor stator is formed with a pair of complementary opposable claw pole stator structures in which each of the stator structures comprises a stator base formed of a plurality of stacked sheet metal laminations. A plurality of stator pole members extend from the stator base and are formed by compression molding of a ferromagnetic material. In one form, the ferromagnetic material is molded in situ on the stator base by positioning the stator base in a compression mold having the slots in which a powdered or flaked ferromagnetic material can be positioned and compressed by a die. In another form, the ferromagnetic pole members may be independently compression molded of powdered or flaked ferromagnetic material and then adhesively bonded to the stacked laminations forming the stator base. In either method, the stacked laminations are formed with a plurality of receptacles for receiving one end of each of the stator poles and holding the stator poles to the stator base.

Abstract: A rotor includes a shaft; a permanent magnet layer; and a retainer comprising a conductive, low magnetic permeability material bound to the rotor shaft. The permanent magnet layer is semi-restricted between the shaft and the retainer. In one embodiment, the magnet layer includes a molded ring magnet. In another embodiment, the magnet layer includes a plurality of magnet segments which can be situated on the rotor in rotor pockets or in a rotor cage. The bond between the retainer and the rotor can be enabled by a cap or by support elements. A high conductivity material can be situated over the retainer with the combination of the retainer and the high conductivity material having a resistivity high enough to minimize space harmonic losses and low enough to minimize time harmonic losses. The high conductivity material can also be applied to induction rotors for excluding high frequency components while permitting penetration of low frequency torque producing fields.

Abstract: A method for obtaining a power system phasor includes sampling a power system signal at instants determined by a nominal power system frequency to provide a plurality of data samples; using the data samples to estimate a phasor having an elliptical trajectory; generating a deviation formula representing a frequency deviation between actual and nominal power system frequencies; and using the deviation formula to perform a coordinate transform of the estimated phasor to provide a scaled phasor having a substantially circular trajectory. If the data samples are unevenly spaced, a method in another embodiment includes minimizing squares of errors between the unevenly spaced data samples and an approximating sinusoidal function of the data samples.

Abstract: A generator for producing electricity at high efficiency from mechanical energy includes a housing, a shaft mounted in the housing, an electrical coil positioned about the shaft and an annular, anisotropic magnet positioned about the shaft adjacent the coil. The magnet has a plurality of circumferentially distributed, alternating magnetic poles. Ferromagnetic flux plates are operatively associated with the magnet and the coil for establishing an alternating magnetic field through the coil as a function of rotation of at least one of the magnets, the coil and the flux plates.

Abstract: A fixture to evaluate stator production quality is placed about a stator core so as to introduce a test winding about the stator without need for hand winding. The fixture includes an inner annulus and an outer annulus each with axial conductors thereon, and top and bottom plates each with conductors thereon. The core is fitted between the inner and outer annuli, and between the top and bottom plates. The inner axial conductors and outer axial conductors are connected to one another at their lower ends through the bottom plate conductors and at their upper ends through the top plate conductors. Once testing is complete, the fixture is easily removed.

Abstract: A method for turn fault detection in a multi-phase alternating current machine includes obtaining instantaneous line-to-neutral voltages from each phase of the machine, calculating the sum of the line-to-neutral voltages, and using the sum to determine whether a turn fault exists. The line-to-neutral voltages can be filtered to reduce harmonics. In one embodiment, deviations in a time-averaged function of the sum are examined. The time-averaged function can be exponentially weighted. Each of the line-to-neutral voltages can be calibrated to remove inherent machine phase impedance imbalance prior to calculating the sum of the line-to-neutral voltages.

Abstract: Rotor temperature in induction motors is estimated without the need for any direct temperature sensors, by using only computer calculations based on data readily available in the motor control center. Thus for any given motor, it is generally possible to predetermine a relationship between rotor temperature and rotor resistance, so that by determining rotor resistance, rotor temperature can be calculated. Rotor resistance, in turn, can be calculated from measured information relating motor slip and motor torque. Any of several methods can be employed for determining torque and slip. Temperature estimation can be obtained by use of equivalent circuit methods, and additional relationships can be obtained from a simplified equivalent circuit.

Abstract: A rotor for use in a line start permanent magnet motor comprises a rotor core having a shaft and including teeth defining slots; a rotor cage, at least a portion of which extends through the slots; and a layer of composite permanent magnet material at least partially coating the rotor core.

Abstract: A permanent magnet motor employing sets of divided magnets on the surface of the rotor enables stator current to be used to control the net flux in the stator teeth, yoke and airgap. Each set of divided magnets circumscribes a respective portion of an arc of 360.degree. about the center of the rotor and is made up of a subset of a number of successive south (S) magnet polarities and a subset of an of successive north (N) magnet polarities arranged such that each subset about the 360.degree. arc is of opposite polarity to the adjacent subset at either side. This enables terminal voltage to be kept constant as speed increases, but with less current than in the case of conventional surface magnet motors.

Abstract: A motor stator comprises a first stator frame part, a second stator frame part including first and second pole portions separated by a stator bridge, and two magnetic arms. Each of two bobbins is wound with a coil and situated on a respective one of the arms. The first and second stator frame parts are coupled by the arms so as to leave an opening between the two bobbins and the first and second frame parts for insertion of a rotor.

Abstract: A seal-less pump and electric motor assembly includes a motor rotor fixed to a driving shaft connected to an impeller in the pump assembly. The rotor and impeller are enclosed in a common housing such that the rotor rotates within any fluid being pumped by the impeller. The portion of the housing circumscribing the rotor includes a plurality of axially extending, circumferentially spaced strips of magnetic material penetrating through plastic material of the housing. Each of the strips coincide with corresponding ones of the pole teeth of a motor stator circumscribing the outer portion of the housing such that the strips in the housing act as extensions of the pole teeth. In one embodiment, the strips of magnetic material in the housing are formed by molding powdered iron in a plastic binder material. The strips are then placed in a mold in which the housing is formed by injecting plastic. The plastic binder in the strips melds with the injected plastic to form a continuous housing for enclosing the rotor.

Abstract: A method for fabricating a stack of motor laminations comprises forming cooling holes in each of the motor laminations and stacking the motor laminations with respective ones of the cooling holes in the laminations at least partially coincident to form a staggered cooling passage by having at least some of the cooling holes extending further into the cooling passage than others of the cooling holes. In one embodiment, the cooling holes can be perturbed cooling holes which are radially displaced from another cooling hole, azimuthally displaced from a hole axis, having an asymmetrical shape, being a different size from another cooling hole, or being shaped so that the rotation and stacking of a subsequently applied lamination results in a situation wherein adjacent cooling holes are not precisely aligned.

Abstract: A method for monitoring a rotor speed of an X-ray tube anode drive includes acquiring axial flux pickup data from the rotor, using the axial flux pickup data to provide a flux spectrum, and estimating the rotor speed by analyzing the flux spectrum. The step of acquiring axial flux pickup data can include situating an axial leakage flux pickup coil so as to pick up a flux signal from an X-ray tube anode drive rotor while the rotor rotates. An analog flux signal can be converted to a digital flux signal and a fast Fourier transform can be used to transform the digital flux signal into a flux spectrum. The flux spectrum can be used to estimate a drive frequency and a slip frequency and the speed can be estimated by subtracting the slip frequency from the drive frequency and dividing by the number of pole pairs of the X-ray tube anode drive.

Abstract: A rotor includes a shaft; a permanent magnet layer; and a retainer comprising a conductive, low magnetic permeability material bound to the rotor shaft. The permanent magnet layer is semi-restricted between the shaft and the retainer. In one embodiment, the magnet layer includes a molded ring magnet. In another embodiment, the magnet layer includes a plurality of magnet segments which can be situated on the rotor in rotor pockets or in a rotor cage. The bond between the retainer and the rotor can be enabled by a cap or by support elements. A high conductivity material can be situated over the retainer with the combination of the retainer and the high conductivity material having a resistivity high enough to minimize space harmonic losses and low enough to minimize time harmonic losses. The high conductivity material can also be applied to induction rotors for excluding high frequency components while permitting penetration of low frequency torque producing fields.

Abstract: A method for fabricating a motor component comprises forming a plurality of substantially parallel electrical current conductors and molding magnetic flux conductive material around at least a portion of each of the plurality of electrical current conductors. In one embodiment the motor component comprises a stator, and the step of forming a plurality of slot liners comprises positioning multi-turn wire coils on a mandrel. In another embodiment, the motor component comprises a rotor, and the step of forming the plurality of substantially parallel electrical current conductors comprises fabricating a rotor cage.

Abstract: A method for detecting turn faults in an induction motor includes obtaining motor current and voltage waveforms and converting the motor current and voltage waveforms to digitized current and voltage waveforms. Fundamental phasors of the digitized current and voltage waveforms are extracted and, a symmetrical component transform is applied to the fundamental phasors to obtain symmetrical component current and voltage phasors including a negative sequence voltage phasor (V.sub.-) and negative sequence current phasor (I.sub.-). A fault injected negative sequence current (Ii.sub.-) is estimated according to the following equation:Ii.sub.- =I.sub.- -V.sub.- /Z.sub.- -Ir,wherein Z.sub.- is a characteristic negative sequence impedance and Ir is a residual injected negative sequence current. The existence of a turn fault is determined by comparing the estimated fault injected negative sequence current with a threshold fault injected negative sequence current.

Abstract: During a learning stage a motor current signal is monitored, and estimated motor torque is used to transform the current signal into a time-frequency spectra including a plurality of segments representative of good operating modes. A representative parameter and a respective boundary of each segment is estimated. The current signal is monitored during a test stage to obtain test data, and the test data is compared with the representative parameter and the respective boundary of each respective segment to detect the presence of a fault in a motor. Frequencies at which broken bar faults are likely to occur in a motor can be estimated using the estimated motor torque, and a weighting function can highlight such frequencies during estimation of the parameter. The current signal can be further subdivided into the segments by monitoring sidebands of the frequency components of current spectrum strips of each segment.

Abstract: In a five-axis magnetic bearing, each of two combined radial and axial magnetic bearing structures includes a radial magnetic stator and a radial magnetic rotor. A shaft supports the rotors of the bearing structures. Each rotor and stator have an asymmetrical orientation such that the bearing structure is capable of creating a force in an axial direction when the bearing structure is excited. A creatable axial force of a first one of the bearing structures is capable of being in sufficient opposition to a creatable force of a second one of the bearing structures so as to maintain the shaft assembly in a desired axial position. The asymmetrical orientation may include, for example, a rotor being physically offset from a stator or a spatial distinction between a surface region of a respective rotor and a surface region of a respective stator. Examples of spatial distinctions include material extensions, notches, and holes.