Abstract: Pursuant to detecting rotor faults in an induction motor by analysis of a frequency spectrum of the current drawn by the motor under test, wherein success of the fault analysis requires an accurate determination of the fundamental frequency of the motor current and the motor slip frequency, method and apparatus are disclosed for determining the fundamental and slip frequency values solely from analysis of the motor current spectra.

Abstract: To detect broken bars in the rotor of induction and synchronous motors, the current drawn by the motor during the transient startup period as the motor runs up to steady state speed is analyzed to identify any dip in the starting motor current amplitude occurring when the motor reaches approximately half-speed. The magnitude of any identified current dip is tested against threshold values to determine if the dip is characteristic of a broken rotor bar condition. Reliable broken rotor bar detection is achieved regardless of whether the motor is loaded or unloaded.

Abstract: A vibratory linear motor system employs a comb-shaped electromagnet to excite transverse mechanical oscillations of a relatively thin, spring-like beam. The electromagnet establishes an approximate standing wave on the beam for which brakes mounted on either side of the beam provide independently established boundary conditions and produce rectified linear motion thereof. The brakes may be electromagnetically, magnetostrictively, or piezoelectrically actuated. An electronic control provides modulated currents to the exciter electromagnet and the brakes in order to control the rectified linear motion of the beam.

Abstract: An electric motor driven blade pitch varying system for the fan blades of an unducted fan type aircraft gas turbine engine utilizes permanent magnet alternating current motors located in the oil sump region of the engine. An alternator driven by the engine generates unregulated variable frequency, variable amplitude power which is rectified and placed on a DC bus. Controlled inverters convert the DC power on the bus to appropriate AC power for the motors. The system incorporates redundancy without significant weight penalty by providing alternators and motors dividing into two independent operating sections on common shafts. Separate electronic circuits are provided to supply power for each sectionalized motor or to rectify power from each alternator section. A common power bus may be used to couple the multiple motors and alternators. The common bus may alternatively receive power from tbe aircraft 400 Hz system or from on-board batteries.

Abstract: In a homopolar, switched reluctance, or interior permanent magnet motor, formed rotor laminations are employed to reduce eddy current losses in the pole faces and body of the rotor. The homopolar and switched reluctance motor lamination is comprised of a magnetic portion having a plurality of pole pieces extending generally radially outward from the core portion and forming a plurality of interpole spaces. Non-magnetic, high resistance segments are bonded between the pole pieces to minimize windage losses and increase strength. The non-magnetic segments may be thinner in the axial direction than the magnetic portion to prevent contact between stack laminations. Additionally, a gap may be left between the interior core portion and the non-magnetic segment to facilitate use of automated welding techniques.

Abstract: In a homopolar, switched reluctance, or interior permanent magnet motor, formed rotor laminations are employed to reduce eddy current losses in the pole faces and body of the rotor. The homopolar and switched reluctance motor lamination is comprised of a magnetic portion having a plurality of pole pieces extending generally radially outward from the core portion and forming a plurality of interpole spaces. Non-magnetic, high resistance segments are bonded between the pole pieces to minimize windage losses and increase strength. The non-magnetic segments may be thinner in the axial direction than the magnetic portion to prevent contact between stack laminations. Additionally, a gap may be left between the interior core portion and the non-magnetic segment to facilitate use of automated welding techniques.

Abstract: A fault management system for a switched reluctance motor detects faults through phase current differential sensing and phase flux differential sensing and isolates any fault by deactivating any faulted phase. Motor operation continues through the remaining phases. A speed control circuit maintains the normal operating speed of the motor, despite the deactivation of one or more phases. Starting the motor when stopped in a "dead zone" created by a faulted phase is accomplished by using the intact phases to generate negative torque to move the rotor out of the dead zone.

Abstract: A winding and method of winding for a submersible linear pump for pumping liquid sodium is disclosed. The pump includes a stator having a central cylindrical duct preferably vertically aligned. The central vertical duct is surrounded by a system of coils in slots. These slots are interleaved with magnetic flux conducting elements, these magnetic flux conducting elements forming a continuous magnetic field conduction path along the stator. The central duct has placed therein a cylindrical magnetic conducting core, this core having a cylindrical diameter less than the diameter of the cylindrical duct. The core once placed to the duct defines a cylindrical interstitial pumping volume of the pump. This cylindrical interstitial pumping volume preferably defines an inlet at the bottom of the pump, and an outlet at the top of the pump.

Abstract: An electromagnetic actuator includes a moving element comprising a plurality of permanent magnets oriented in alternating magnetic pole position so as to present a sequence of alternating north-south magnetic poles. The magnets can be angularly oriented within a magnetic structure serving to concentrate magnetic flux and focus such flux at the surface of the structure. Alternatively, the magnets are surface mounted within a structure of non-magnetic material. The actuator includes opposed electro-magnetic stators between which the moving element is positioned.

Abstract: A method and apparatus for detecting rotor faults in an induction motor. Such induction motors have a stator and a rotor comprising a multiplicity of rotor bars. The flux around the rotor bars is detecte at a predefined flux detection point in the motor, generally by using a coil wound around one of the stator teeth. A synchronization signal is generated once per revolution of the rotor when a predefined position on the rotor is closest to a stator reference point, usually the flux detection point. The detected flux signal is filtered to reject signals in a predefined frequency band around the frequency at which the rotor bars pass the flux detection point, and then it is synchronously time averaged. Averaging requires that corresponding portions of the flux signal, for a series of rotor revolutions, be added, and the synchronization signal is used as a reference for matching corresponding portions of the flux signal.

Abstract: A method and apparatus for detecting rotor faults in an induction motor. A flux sensor generates a flux signal corresponding to the magnetic flux at a predefined flux detection point external to the motor. A current sensor generates a current signal proportional to the current drawn by said motor. A time series of data points is stored, representing the values of the flux signal and the current signal over a period of time. The time series are transformed by FFT into a set of flux spectra and into a set of current spectra. Then the line frequency of the motor's power supply is determined by finding the maximum of the current spectra. Similarly, the slip frequency of the motor is determined by finding the maximum of the flux spectra in a predefined spectral range (e.g., below 2 Hz). The analysis of the rotor is then performed by comparing the amplitude of the current spectra, at a set of rotor fault harmonic frequencies, with specified fault threshold criteria.

Abstract: An electric machine has a stator body formed of a coil of concentric layers of amorphous metal tape and slots are formed in one end of the coil for receiving a stator winding. A rotor structure having permanent magnet poles embedded therein is placed adjacent the end surface of the stator and is coupled thereto through the axial gap between the stator and rotor. The magnets are held in place in a nonmagnetic matrix which consists of an epoxy fiber laminate material. By enlarging the outer diameter of the rotor with the epoxy fiber laminate material, the rotor serves as an integral flywheel structure.

Abstract: An induction motor of the squirrel cage type is disclosed. The stator body and rotor body of the motor are each disclosed as being made of a coil of concentric layers of a thin metal tape which is slotted to receive the rotor and stator windings. The motor is similar to a conventional disk type motor except that the secondary, instead of being a solid copper or aluminum disk, is a coil of concentric turns of notched metal tape which improves the efficiency by reducing the effective air gap. A method of manufacture of the coil of tape is disclosed wherein identical notches are formed in the tape with a progressively increasing spacing between the notches which permits the notches to come into radial register with one another to form a slot in the end of the stator or rotor body.

Abstract: Amorphous metal ribbon and thin conventional magnetic material is fully cut through by an electron beam and has no or minimal bead on the edge. The ribbon is bent around a roller while under the electron beam and centrifugal force removes molten metal from the cut. An alternative method is to partially cut through and mechanically deform the material to break the thinned section metal bridges remaining below the cut. Motor laminations so cut have negligible increase in thickness and stack compactly.

Abstract: A rapid method of cutting thin amorphous metal sheet material is to use a focused heat source such as a laser beam or electron beam to heat local regions of the material above the crystallization temperature and form brittle crystalline lines along which the material fractures when it is mechanically deformed as by passage through a set of rollers. The material is not melted and does not form burrs. A higher packing factor is possible for motor and transformer laminations.