Abstract: A rotor analyzer for an induction motor or generator checks and quantifies the integrity of a rotor that is not currently installed within its stator. The analyzer includes an electromagnetic coil that exposes the bars of a rotor to a pulsating magnetic field to induce a current through the bars. At the same time, the rotor is slowly rotated to sequentially expose each bar. A magnetic field created by the induced current in the bars induces an analog signal within a search coil. The analog signal is converted to digital and inputted to a microprocessor system. The system interprets the input data and manipulates it to provide a clear, understandable indication of the rotor's condition, such as the relative impendence of each bar. The system also determines how many bars are within a rotor having an unknown number of bars.

Abstract: In a device for the investigation of components of a generator which border on a machine air gap (29) between stator and rotor (22), with the rotor (22) built in, by means of at least one movable inspection probe (35), a simple, flexible and rapid mounting is ensured in that the device comprises a base unit (31) which can be secured to the rotor (22) on both sides, and which permits at the least one inspection probe (35) to move in the machine air gap (29), both in an axial direction with respect to the generator axis and also in the circumferential direction of the machine air gap (29) over the whole circumference of the rotor.

Abstract: In a rotary assembly comprising a rotor mounted in rotation in a stator about a mean axis or rotation, a radial position sensor comprises three induction sensors distributed in the stator substantially at 120° from one another around the rotor and equidistant from the mans axis of ration. The induction sensors are cabled in star connection with a common connection point, and are powered by a balanced three-phase sinusoidal voltage source with neutral point. The output voltage, present between the common connection point and the neutral point of the balanced three-phase sinusoidal voltage source, is processed by signal processing means which determine its amplitude and its phase relative to the voltage delivered by the balanced three-phase sinusoidal voltage source. Thus, from only three sensors, two signals are obtained constituting the amplitude image and the angular position of the radial displacement of the rotor gravity axis in the stator.

Abstract: A system for measuring dynamic loads in a rotordynamic system having a rotor includes a magnetic bearing disposed around the rotor and having a plurality of magnets and at least one fiber optic strain gage associated with a pole of a respective magnet. The fiber optic strain gage is operable to detect a strain on the respective pole resulting from the dynamic loads. The detected strain is indicative of the dynamic loads.

Abstract: A testing apparatus determines when an electric motor is acceptable based on measured parameters and fuzzy logic. The testing apparatus measures the following motor parameters: a time for the motor to reach a running speed in a steady-state, thus forming a time-to-speed; a difference between an instantaneous speed and an average speed in the steady-state, thus forming a speed variation; a maximum value of the motor current, thus forming a maximum current; a motor current in the steady-state, thus forming a running current; and a motor vibration energy in the steady-state, thus forming a vibration energy. Based on the measured motor parameters, the testing apparatus then uses fuzzy logic to determine when the motor is acceptable.

Abstract: For detecting a coil short-circuit in an electric motor such as a switched reluctance motor, an apparatus includes a first phase coil, a second phase coil, and a third phase coil. Through each of the coils, a current, whose amount is sensed by a current sensor, flows in such manner that the amount ranges from zero to a reference current amount in a reference set-up time duration. If the detected amount of current by the current sensor becomes the reference current amount in a time duration which is shorter than the reference set-up time duration and the resultant condition continues for an another reference time duration, it is regarded that a short-circuit occurs in the phase coil corresponding to the current sensor and the apparatus stops the electric motor.

Abstract: In an arrangement for detecting pinching situations in electric drives, provided in particular for window and sunroof openers in motor vehicles, the voltage induced in the armature of the motor is used, the induced voltage being determined from the voltage across the motor terminals and the current flowing in the armature, in particular as the difference between the voltage across the motor terminals and the product of the armature current by the armature resistance which is obtained periodically whenever possible. The armature resistance is obtained from the voltage across the motor terminals and the blocking current of the motor, the latter being determined by extrapolation of the armature current determined at a certain point in time. The armature current is measured using a shunt resistor and optionally amplified, and the current signal obtained is averaged using a microcontroller-controlled integrator with adjustable, computed integration periods, and digitized using an analog-digital converter.

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: A current monitoring system for an electric motor, whereby the current is halted to the motor if the electrical load exceeds calculated electrical load limits. The system includes a current measuring device, sensors for detecting operational functions, a system for setting an electrical current limit setpoint, and a switch for halting application of electrical current to the motor. A method of halting an electrical motor if the electrical load exceeds a calculated electrical current limit is also disclosed.

Abstract: A method for removing spurious signals in a process of motor current signature analysis of an electric motor (24 or 33) includes creating an electronic model of the motor, acquiring simultaneous measurements of voltage and current at the motor, applying the voltage measurement to the motor model and determining an equivalent current produced in the motor model by the applied voltage, subtracting the equivalent current from the current measurement to produce a corrected motor current, and processing the corrected motor current through motor current signature analysis. For an ac motor (33), the method includes extracting signals corresponding to the fundamental excitation frequency from the voltage measurement to produce an interfering voltage, processing the interfering voltage through the motor model to produce a corresponding spurious current signal, and subtracting the spurious current signal from the measured current to produce the corrected motor current signal for analysis.

Abstract: A method and apparatus are provided for measuring a quality of insulation surrounding rotor bars of a rotor of a squirrel cage motor. The method includes the steps of applying an alternating magnetic flux to opposing ends of the rotor measuring a power level absorbed by the rotor as a result of the applied alternating magnetic flux. The method further includes the step of using the measured power level as a relative measure of the quality of the insulation of the rotor bars.

Abstract: A miniature air gap inspection device permits in-situ inspection of a generator field and stator core having entrance gaps as little as 0.5" and larger. The inspection device passes through a radial air gap between a core iron and a retaining ring of the generator, and thus, removal of the generator field is not necessary. The device includes a tractor section having a tractor frame attachable to the retaining ring for selective circumferential positioning about the field. A mast section is coupled with the tractor frame and includes an extendible mast. An inspection head is attached to the extendible mast and is axially extended and retracted in the gap by the mast. The inspection head supports at least one inspection tool for performing the in-situ generator inspections.

Abstract: The present invention provides a system and method for monitoring an electrical signal appearing on a rotating machine shaft. The system comprises a probe assembly for placement against the rotating machine shaft that is in electrically conductive contact with the shaft. The probe assembly includes at least one circuit for receiving the electrical signal from the rotating machine shaft and producing various electrical signals that are read by a data processing system, which is coupled to the circuit. The data processing system determines from the electrical signal obtained from the circuit, the RMS AC voltage, DC voltage, peak voltage, and the RMS AC and DC current through two different resisters that are all appearing on the rotating machine shaft. The data processing system also performs Fast Fourier Transforms on the RMS voltage and current signals and produces a frequency spectrum over time.

Abstract: A safety compliance test instrument includes circuitry for performing insulation resistance and ground circuit tests such as a ground bond test, as well as high voltage AC and DC dielectric withstand or hipot tests. A micro-processor based controller provides control signals to a common power circuit, and accepts input of test parameters for all four tests through an integrated user interface including a keypad and menu display.

Abstract: In a method for determining the state of strength of winding overhangs (2) of electric machines, at least one sensor (3), which is arranged on a winding end (4) of a winding overhang (2) and is connected to an evaluation unit (5) is used to determine a vibration amplitude (A) of the winding end (4), and the associated phase (.phi.). The phase (.phi.) of the vibration amplitude (A) is determined in this case with reference to a phase of an electric current flowing through the winding end (4). The quotient (.DELTA.A) of the vibration amplitude (A) and an amplitude reference (A.sub.ref) dependent on the electric current, and the quotient (.DELTA..phi.) of the phase (.phi.) of the vibration amplitude (A) and a phase reference (.phi..sub.ref) dependent on the temperature of the winding overhang (2) permit the state of strength of winding overhangs to be determined and causes to be located in the event of a change in the vibration amplitude.

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: The method consists in positioning a probe in front of a pair of teeth provided on the face of the magnetic circuit of an electric machine. The probe has spaced apart magnetic prong portions having respective end faces adapted to match the teeth of the pair with the end faces in registry with the teeth. The prong portions are respectively provided with an excitation winding and a measurement winding. The excitation winding is excited to induce a magnetic flux in a test zone formed of the teeth in front of the probe and a portion of the magnetic circuit extending therebetween. The current flowing in the excitation winding and the voltage across the measurement winding are measured for calculating a resulting power which is indicative of the condition of the test zone. The apparatus is formed of the probe and electronics carrying out the above functions.

Abstract: The inspection apparatus for inspecting performance of a structure such as stator windings of an electric rotating machine of the invention comprises a probe including a measuring element, an arm unit and a cylinder face circumferential moving apparatus. The arm unit has an arm link section supporting the probe (mainly comprising a leading end link assembly and an arm posture keeping mechanism), an arm housing section (mainly comprising a guide rail) regarding driving of this arm link section, and an arm driving mechanism. The arm driving mechanism causes the leading end link assembly to project from the guide rail at an angle toward a measuring position side of the stator windings relative to the axial direction of the rotor unit, while causing the arm link section to travel along the guide rail. The arm posture keeping mechanism is provided with a link wire and a spring, and maintains a straight arm posture of the leading end link assembly after projection from the guide rail.

Abstract: A method and apparatus for detecting winding errors in electric motor stators having a plurality of field windings is disclosed. The method involves the steps of applying a current source to at least one of the field windings to generate a magnetic field within the stator, measuring the polarity and strength of the field for each winding at preselected radial and angular positions about a circumference of the stator bore, and comparing the measured values to recorded values of radially and angularly corresponding measurements for a reference motor stator. Preferably, the current source is applied to each of the windings in succession. The apparatus includes a terminal block, switch, and power supply to connect a source of current to each field winding in succession to generate a magnetic field within the stator.

Abstract: A high speed dynamic run-out testing apparatus includes a drive source rotatable at a high speed and having an output shaft, a main shaft coupled coaxially with the output shaft of the drive source, a non-contact bearing for rotatably supporting the main shaft in a non-contact fashion, a testpiece carrier shaft provided on one side of the main shaft remote from the drive source for supporting a cylindrical testpiece mounted on such testpiece carrier shaft, and a non-contact displacement detector for measuring a displacement of the cylindrical testpiece.

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: A method for nonintrusive detection of anomalies in electric machines. A flux coil is positioned external to the motor to obtain magnetic leakage flux measurements, which are transformed to the frequency domain to obtain a flux spectrum. Asymmetry-producing faults, such as turn-to-turn stator winding shorts, produce changes in the amplitudes of individual frequencies and groups of frequencies within a defined slot pass family of frequencies of the flux spectrum. The measured amplitudes of the slot pass family of frequencies are compared to reference and trend data. Significant changes in the slot pass frequency amplitudes indicate the presence of a machine fault or other anomalous condition. Significant changes are determined by comparing individual amplitudes and groups of amplitudes of the slot pass family of frequencies to an absolute or delta threshold value.

Abstract: A motor current signal is monitored during a learning stage and divided into a plurality of statistically homogeneous 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 bearing faults are likely to occur in a motor can be estimated, and a weighting function can highlight such frequencies during estimation of the parameter.

Abstract: An improved alternator/starter testing device includes an electronic voltage regulator for regulating the output of an externally regulated alternator. A selectable load switch allows so-called "high output" alternators to be tested without damaging the voltage regulator. For certain types of internally regulated alternators, the testing device includes a meter disconnect circuit, coupled to an "energize" switch in the testing device, which operates to disconnect the testing meter during a period in which the energize switch is temporarily depressed to supply power to an internally regulated alternator under test, thus preventing misleading test results if a defective alternator is tested. Internal thermal circuit breakers are provided at strategic locations in the testing device to prevent internal circuit damage due to defective alternators and starters.

Abstract: A circuit detects insulation defects in a coil assembly including a plurality of series connected coils. A first voltage pulse is applied to a first coil of the coil assembly, a second voltage pulse is applied to a second coil of the coil assembly, the first and second coils being substantially diametrically opposite to one another, and the first and second voltage pulses being substantially equal to one another and oppositely poled relative to the coil assembly. A first voltage waveform across the first coil is monitored, and a second voltage waveform across the second coil is monitored. A first signal is derived from the first voltage waveform, a second signal is derived from the second voltage waveform, and a differential percentage value based on the first signal and the second signal is computed. An insulation defect is then determined based upon the differential percentage value.

Abstract: An apparatus detects a ground fault of an exciting circuit and a field circuit of an AC exciting variable speed rotating machine. The exciting circuit outputs an excited voltage controlled a frequency and/or an amplitude, and the field circuit of the AC exciting variable speed rotating machine is applied a field current by the excited voltage of the exciting circuit. A ground resistance is connected between a neutral point and a ground. The apparatus detects a current flowing from a ground to a neutral point through the ground resistance, and detects the ground fault based upon the detected current. Therefore, the apparatus can detect a ground fault of a field circuit and an exciting circuit of an AC exciting rotating machine during the AC exciting rotating machine operation with certainty.

Abstract: An electric rotating machine comprises a rotor body of cylindrical structure and a stator body covering an outer peripheral portion of the rotor body in a non-contact fashion. The stator body includes a stator winding formed with an insulation layer and arranged radially outward of the rotor body with a clearance from the rotor body and a stator core which supports the stator winding.

Abstract: In the no-load state of operation of a running asynchronous motor, after separating the no-load copper losses as well as the sum of the iron losses and friction losses and taking into consideration the rated current of the motor and the rated rate of rotation, an upper limiting value of the rated efficiency of the motor is determined while assigning the iron losses and the friction losses to the stator losses and a lower limiting value of the rated efficiency of the motor is determined while assigning the iron losses and the friction losses to the rotor losses.

Abstract: A circuit to monitor a short circuit (or a line interruption) in an inductive circuit which is connected to a signal-processing circuit through a high-ohmic filter circuit. The monitoring circuit is formed as a component part of or as an additional element to the signal-processing circuit and initiates a test cycle to determine the inductance of the circuit to be monitored when, for example, the ignition of an automotive vehicle is turned on when the inductive circuit is used in the circuitry for sensing wheel rotation behavior of an automotive vehicle.

Abstract: A single source of energy is used to determine up to four armature coil or winding resistances and effectively up to four armature winding weld resistances for each test connection or index position of an armature being tested to thereby reduce the test time required for testing commutated armatures while reducing the complexity of the apparatus and test methods applied. Two preferably substantially diametrically opposite driven current paths through the armature windings are driven, and current and voltage measurements are taken at various commutator bars including commutator bars located adjacent current input ends and current output ends of the driven current paths. The resulting measurements and computations using these measurements are used to determine the winding resistances and ultimately the winding weld resistances for armatures and, in particular, for testing armatures for compliance with required specifications.

Abstract: A method and apparatus for testing electric motor armatures includes a non-metallic chuck for supporting each armature during testing. The chuck includes three major components, namely, a lower saddle, an upper saddle, and an armature positioning mechanism. The lower saddle is attached to a lifting cylinder and carries each armature from a conveyor to a testing station. The upper saddle is permanently associated with the testing station. The armature positioning mechanism is attached to the upper saddle and includes a spring loaded metal dog which engages each armature as it is being lifted into position to rotate the armature into the proper position so that electrical contact wires extended from a test head will contact the contact bars of the armature commutator. Both the upper and lower saddles are made from a non-magnetic material, such as Nylon, but are provided with ceramic rollers which engage the armature to prevent wear. A cylinder retracts the metal dog during surge testing.

Abstract: A system and method for testing an electrical generator of the type having a rotor (14) and a stator (12) includes or utilizes a movable carriage (22) having testing equipment which is sized to fit between the rotor (14) and stator (12) and is positionable over a selected stator (12) slot so as to be able to axially traverse the selected stator (12) slot, at least one sensor for sensing whether the movable carriage (22) is centered in an optimum position with respect to the selected stator (12) slot; and structure for centering the movable carriage (22) with respect to the optimum position if the sensor indicates the movable carriage (22) is not so centered, whereby accuracy of any testing by the testing equipment is optimized.

Abstract: An improved armature testing apparatus and method are provided. The individual resistances of two commutator bar lead connections can be simultaneously measured in a single measurement step. Further, the resistances of two armature coil can be determined in the same step. The present invention makes it possible to measure individual commutator coil lead connections more quickly than was previously possible.

Abstract: A motor current analysis method and apparatus for monitoring electrical-motor-driven devices. The method and apparatus utilize high frequency portions of the motor current spectra to evaluate the condition of the electric motor and the device driven by the electric motor. The motor current signal produced as a result of an electric motor is monitored and the low frequency components of the signal are removed by a high-pass filter. The signal is then analyzed to determine the condition of the electrical motor and the driven device.

Abstract: Motor current and voltage waveforms are measured and converted to digitized current and voltage waveforms. A weighted discrete fourier transform is applied to the digitized current and voltage waveforms to obtain negative sequence current and voltage phasors; and the negative sequence current and voltage phasors are used to determine the existence of a turn fault. The use of the negative sequence current and voltage phasors can be performed by employing one of several techniques. In a first embodiment, an apparent negative sequence impedance is estimated by dividing the negative sequence voltage phasor by the negative sequence current phasor for comparison with a threshold negative sequence impedance. In a second, related embodiment, a current differential is estimated by dividing the negative sequence voltage phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence current phasor for comparison with a threshold current differential.

Abstract: A method and apparatus are provided for determining angular alignment between a lamination stack, a commutator, and coil windings of an armature for an electric motor. The apparatus has a body with an aperture for extending about the commutator, and a post for fitting into the lamination stack to locate an indicator slot and graphic symbols relative to the lamination stack for visually comparing alignment between the lamination stack, the commutator, and the coil windings.

Abstract: A method is specified for detecting ground faults on the conductors of electrical machines, in which method the fault resistance (Rf) is directly calculated in a numerical evaluation unit (7) from the injected (Ui) and the measured (URE) voltages. Since the fault resistance is explicitly calculated and displayed, it is independent of influences from the ground reactance. Moreover, there is no need to, for each machine, characteristics for drawing conclusions on the fault resistance. Moreover, the influence of ageing, temperature fluctuations, injection level fluctuations etc. is eliminated due to the numerical calculation. (FIG.

Abstract: Apparatus may be inserted in the casing of a d.c. motor or a d.c. generator for measuring not only the magnetic fields prevailing in the machine but developing other useful information. The magnetic fields between the field poles and the armature, and also the armature/mmf fields aligned with the brushes may be measured. The measurements of the fields permits a complete plot of the fields in the machine and also permits a test to be performed to see if the brushes are at their optimum positions. If a brush is not at its optimum position, the brush may be shifted back and forth until the maximum mmf, due to the current through the armature is aligned midway between the leading and trailing ends of the brush area coverage on the commutator.

Abstract: A method and apparatus for determining the resistance of the coils and commutator connections in an armature of an electric motor wherein a current is generated between a first commutator segment and a commutator segment located at least three segments beyond said first segment, a first voltage is measured across the first commutator segment and an adjacent second commutator segment, a second voltage is measured across the second commutator segment and an adjacent third commutator segment, and a third voltage is measured across a pair of commutator segments which are adjacent to the first commutator segment. After the three voltages are measured, the current is disconnected, and a voltage is generated across two commutator segments spaced at least three segments beyond the first segment. The generated voltage is adjusted so that the voltage measured across the second and third commutator segments equals the previous measurement, and the voltages are remeasured.

Abstract: There is disclosed an apparatus and method for determining locked rotor test data for three-phase alternating current motor without mechanically coupling the rotor to any instrumentality. The "locked rotor" test is conducted by connecting a source of single-phase alternating current with a variable frequency to the field windings of a three-phase a.c. motor. The frequency of the voltage source is varied from approximately the rated frequency to a lower frequency and the input electrical power and the input voltage are recorded at two or more data points defined by two or more frequencies between the rated frequency and 0. The single-phase input power data and the single-phase input voltage data is then scaled by a scaling factor to convert it to equivalent three-phase locked rotor data. Particularly, the single-phase input power is multiplied by 1.515 to convert it to equivalent three-phase input power, and the single-phase input voltage is multiplied by 0.

Abstract: A system and method for testing an electrical generator of the type having a rotor (14) and a stator (12) includes or utilizes a movable carriage (22) having testing equipment which is sized to fit between the rotor (14) and stator (12) and is positionable over a selected stator (12) slot so as to be able to axially traverse the selected stator (12) slot, at least one sensor for sensing whether the movable carriage (22) is centered in an optimum position with respect to the selected stator (12) slot; and structure for centering the movable carriage (22) with respect to the optimum position if the sensor indicates the movable carriage (22) is not so centered, whereby accuracy of any testing by the testing equipment is optimized.

Abstract: A stator testing device for a dynamoelectric machine formed from a plurality of laminations defining a plurality of substantially parallel stator teeth each extending over a preselected length of the stator. The stator testing device includes a housing having a bottom face adapted to be disposed adjacent the stator teeth and a face cover extending outwardly from said bottom face. A chattock coil for detecting stator axial currents is disposed within said housing. The chattock coil has a pair of end portions with bottom surfaces each extending to the bottom face of said housing. A pair of brackets are removably attached to the face cover of said housing, and a magnet is removably attached to each bracket. The magnets are located on the brackets so that the bottom surfaces of the pair of magnets are positioned adjacent to selected corners of adjacent stator teeth and remain in positional relationship to the selected corners as the housing is moved over a preselected length of said stator.

Abstract: An electrical generator inspection system comprises an electro-magnetic core imperfection detector that provides an analog signal representative of fault currents detected between adjacent laminations of a stator core; an analog-to-digital converter coupled to the detector for converting the analog signal to a digital signal; a digital filter coupled to the output of the converter for digitally filtering the digital signal to remove noise therefrom; and means for storing predetermined signal criteria and for comparing the filtered digital signal to the predetermined criteria to determine the location of the insulation defects along the stator core. In one embodiment, the system further comprises means for storing the filtered digital signal in a memory.

Abstract: An apparatus for measuring the electrical time constant of the quadrature-axis damper of a synchronous machine is designed such that a voltage from a d.c. power source is applied by switching to armature windings of two. phases, so that an armature current rises and thereafter maintains a constant value. A current induced on a quadrature-axis damper diminishes at a rate determined by the quadrature-axis damper time constant, and this decreasing current and the constant armature current flow inside the synchronous machine to produce a constant resistance drop by resistance of the armature windings and the armature current. In this time, the length of time length until the voltage waveform falls to a prescribed level is measured as the time constant of the quadrature-axis damper with such a measuring device as an electromagnetic oscilloscope.

Abstract: Circuit ends of a cancel loop circuit and a frequency generator circuit are connected with circuit lands in such a manner that the two circuits are not allowed to electrically communicate with each other. The cancel loop circuit and the frequency generator circuit are subjected to an electrical conductivity test to detect any short circuit therebetween. After successful testing, the lands located adjacent each other at one side of the circuits are connected with each other, thereby electrically communicating the cancel loop circuit and the frequency generator circuit to obtain a completed coil circuit.

Abstract: A high frequency surge tester includes a high frequency detection circuit which is used to detect microfracture defects in the insulation of wire on wound coils. The high frequency detection circuit includes a high-pass filter which isolates an errant voltage response so that it can be integrated and compared to threshold limits to determine the magnitude of defects. The surge tester also detects shorts between coils and shorts between turns of the same coil.

Abstract: In the device for detecting partial discharges in winding elements of an electrical machine, the winding element to be investigated is sampled over its length, with high voltage applied, by means of a drivable probe and the radio frequency signals initiated by the partial discharges are received by means of an antenna. The antenna signal is detected and evaluated in a test set (11) connected downstream. The probe is arranged on a support which can be conveyed, under remote control, in the machine longitudinal direction, by means of tension cables (4, 5) or an axle rod, or is provided with a dedicated drive.

Abstract: An automotive charging circuit fault detection circuit includes a pseudo stator-phase signal generator and a stator-phase existence circuit for determining if a stator-phase signal is below a predetermined threshold. A pseudo stator-phase signal control circuit selectively applies the pseudo stator-phase signal to replace the stator-phase signal when the stator-phase existence circuit determines that the stator-phase signal is below the predetermined threshold. A voltage detector circuit continues the application of the pseudo stator-phase signal if an output voltage from the charging circuit is above a minimum voltage. A timer times a predetermined time the stator-phase signal is below the predetermined threshold to enable the voltage detection circuit, and a warning indicator provides a warning if the pseudo stator-phase signal is applied and if an output voltage from the charging circuit is below the minimum voltage.

Abstract: In order to determine the occurrence of a stator fault in an induction motor during operation of the motor, the axial leakage flux is monitored during operation of the motor. The occurrence of a stator fault is detected by observing a change in selected harmonic components of the axial leakage. The angular position of the fault with respect to a datum position is determined by noting and recording changes in the axial leakage flux at a plurality of positions distributed symmetrically around the axis of the motor and computing the angular position by triangulation. The axial leakage flux is detected by individual search coils located at said plurality of positions.