Transformer Patents (Class 324/547)
  • Publication number: 20020047714
    Abstract: A diagnosis apparatus (20) mounted to a separable transformer includes an arithmetic control section (27) for inputting, through a differential amplifier (24), a signal smoothing circuit 25 and a voltage detecting section (26), a mutual induction signal generated in a primary coil (11) of the separable transformer when dc power from a dc power supply section (21) and an ac signal from an oscillator (22) are applied to a capacitor (C) which cooperates with the primary core to form a resonance circuit. The arithmetic control section determines the presence or absence of a wire breakage or short-circuit failure in a secondary-side closed circuit of the separable transformer by comparing a frequency characteristic of mutual induction signal, determined based on mutual induction signals successively supplied thereto while the frequency of the ac signal from the oscillator varies, with frequency characteristics for normal, wire breakage and short-circuit conditions stored beforehand in a storage section (28).
    Type: Application
    Filed: October 30, 2001
    Publication date: April 25, 2002
    Inventors: Koichi Murata, Yasunori Habiro, Dongzhi Jin, Fumihiko Abe, Hajime Mochizuki
  • Patent number: 6369582
    Abstract: The winding testing unit provides a system and method for determining a characteristic signature of a winding residing in a device, such as a transformer or generator. A pulse/signal generator applies a suitable number of non-precise and non-identical pulses to the winding. A sensor detects output pulses after each applied input pulse has propagated through the winding. Data corresponding to the applied input and the detected output pulses are stored as data pairs in a memory. The processor executes logic to compute the auto-spectral density (Gxx) and the cross-spectral density (Gxy) for the data pairs. The logic then computes the characteristic signature, H(f), for the winding such that H(f) equals the average of Gxy divided by the average of Gxx for the data pairs. Comparison of the characteristic signatures over a period of time indicates winding deformation or displacement during the time period.
    Type: Grant
    Filed: May 3, 2001
    Date of Patent: April 9, 2002
    Assignee: Georgia Tech Research Corporation
    Inventor: Larry T. Coffeen
  • Publication number: 20020011848
    Abstract: The on-line winding test unit determines a characteristic signature of a monitored winding(s) in a transformer, generator, or the like. A sensor detects incoming pulses, originating elsewhere on the energy delivery system, applied to the winding. A sensor detects output pulses after each input pulse has propagated through the winding. Data corresponding to the input and output pulses are stored. A processor computes the spectral densities of the data records. The logic then computes the characteristic signature, H(f), for the winding such that H(f) equals the average of Gxy divided by the average of Gxx for the valid data. Coherence is used to determine a valid H(f). A comparison of the H(f)'s over elapsed time using an error function indicates winding deformation or displacement.
    Type: Application
    Filed: May 3, 2001
    Publication date: January 31, 2002
    Inventor: Larry T. Coffeen
  • Patent number: 6340890
    Abstract: A method and apparatus for location of partial discharges in an electric high-voltage apparatus, such as a power transformer, which is arranged in a container filled with an insulating medium is provided. At least three ultrasonic detectors are applied with mutually known positions on the outside of the container and in acoustic contact therewith. The times of arrival of a wavefront arriving at the detectors and originating from a partial discharge are determined, and on the basis of the times of arrival and on the basis of the known mutual positions of the detectors, the direction the partial discharge is determined.
    Type: Grant
    Filed: August 6, 1997
    Date of Patent: January 22, 2002
    Assignee: ABB Research, Ltd.
    Inventors: Tord Bengtsson, Mats Leijon
  • Patent number: 6323655
    Abstract: A method and device for detecting partial discharges in an electrical apparatus placed in a tank filled with oil, wherein the tank wall is provided with at least one drain tap. The device includes a probe mounted on a carrier that is movable through the opened drain tap into the tank. To move the probe into the tank while avoiding leakage of the oil, a sleeve maybe coupled to a flange of the drain tap an the carrier may be moved within the sleeve. The probe may be moved so that it at least coincides with the inner surface of the tank wall, or even further, and then measurements may be performed to detect partial discharges.
    Type: Grant
    Filed: August 25, 1999
    Date of Patent: November 27, 2001
    Assignee: N.V. Kema
    Inventors: Yan Hong Fu, Wijnand Reijer Rutgers
  • Publication number: 20010038290
    Abstract: The winding testing unit provides a system and method for determining a characteristic signature of a winding residing in a device, such as a transformer or generator. A pulse/signal generator applies a suitable number of non-precise and non-identical pulses to the winding. A sensor detects output pulses after each applied input pulse has propagated through the winding. Data corresponding to the applied input and the detected output pulses are stored as data pairs in a memory. The processor executes logic to compute the auto-spectral density (Gxx) and the cross-spectral density (Gxy) for the data pairs. The logic then computes the characteristic signature, H(f), for the winding such that H(f) equals the average of Gxy divided by the average of Gxx for the data pairs. Comparison of the characteristic signatures over a period of time indicates winding deformation or displacement during the time period.
    Type: Application
    Filed: May 3, 2001
    Publication date: November 8, 2001
    Inventor: Larry T. Coffeen
  • Patent number: 6313640
    Abstract: A method and system diagnose and measure partial discharge on-line in a power transmission system. A first wideband directional clamp-on detector detects pulses corresponding to partial discharge transmitted via a transmission line. A second wideband directional detector detects pulses corresponding to partial discharge output from at least one bushing tap of a high voltage device. The first and second pulses are nulled and then added and/or subtracted, and a diagnostic and measurement system analyzes the results to determine whether the high voltage device and/or an external source produces partial discharge, determine the type of discharge, and measure the level of discharge. For analysis of internal partial discharge, external partial discharges are rejected. The diagnostic and measurement system simultaneously analyzes multiple phases of the output of the high voltage device, while the device is energized. A method and system also diagnose and measure partial discharge off-line in a high voltage device.
    Type: Grant
    Filed: February 3, 1998
    Date of Patent: November 6, 2001
    Assignee: ABB Power T & D Company, Inc.
    Inventors: Chaoukat Nabih Nasrallah, Arthur Sherman Morris, III
  • Patent number: 6313642
    Abstract: A system for testing an arcing fault detection system in an electrical distribution network having a line conductor carrying an electrical signal between a power source and a load, the arcing fault detection system including a sensor coupled to the line conductor for monitoring the electrical signal and generating a sensor signal representing the electrical signal, the arcing fault detection system generating an arc-indicative signal in response to the sensor signal having characteristics indicative of an arcing fault. The testing system couples the sensor to a test line simultaneously with the line conductor and periodically produces a test signal on the test line. The sensor simultaneously monitors the test signal and the electrical signal and produces a sensor signal representing both the test signal and the electrical signal when the test signal is present on the test line.
    Type: Grant
    Filed: January 24, 1997
    Date of Patent: November 6, 2001
    Assignee: Square D Company
    Inventor: Stanley J. Brooks
  • Patent number: 6307383
    Abstract: An apparatus is disclosed for testing the integrity of inductive coils such as yokes, flyback transformers, and the like. The apparatus includes a compact housing which makes it portable and convenient for field use. The apparatus includes circuitry disposed in the housing for inducing current through the inductive coil being tested. An array of LED's is provided to give the operator a visual display which is indicative of the condition of the inductive coil. The apparatus also includes means for connecting a meter or oscilloscope to the circuit in order to examine the electrical signature from the inductive coil being tested.
    Type: Grant
    Filed: July 30, 1996
    Date of Patent: October 23, 2001
    Inventors: Elver B. Kephart, Jr., Nove J. Kephart, Sr.
  • Patent number: 6288551
    Abstract: In an arrangement that can be implemented with a simple circuit, the load is connected in parallel to an additional resistor. The primary-side input resistance of the transformer is measured, and when the input resistance differs from a predefined value, a load malfunction is signaled.
    Type: Grant
    Filed: February 18, 1998
    Date of Patent: September 11, 2001
    Assignee: Robert Bosch GmbH
    Inventors: Erich Zabler, Anton Dukart
  • Publication number: 20010013784
    Abstract: A method of monitoring contact burnoff in tap changers operating under load in which the load current is measured and for nominal variation of the voltage of the particular tap parameters are stored which are used to calculate the burnoff rate per contact per switching operation. From these values the cumulative burnoff rate of both the switching contact and resistance contact are determined and compared with limits or threshold values.
    Type: Application
    Filed: January 29, 2001
    Publication date: August 16, 2001
    Applicant: Maschinenfabrik Reinhausen GmbH
    Inventors: Rainer Frotscher, Dieter Dohnal
  • Patent number: 6184690
    Abstract: A testing surge tests all of the individual coils within a coil assembly or multi-coil winding simultaneously. A pickup device is positioned adjacent each of the coils being tested. A voltage pulse is applied across the multi-coil winding. Each of the pickup devices generates a signal having a waveform representative of the magnetic field generated by the coil adjacent thereto in response to the voltage pulse. These signals are compared to each other to identify insulation defects, winding defects and polarity problems within the coils.
    Type: Grant
    Filed: January 11, 1999
    Date of Patent: February 6, 2001
    Assignee: Fisher Data Products, Inc.
    Inventor: James Allan Fisher
  • Patent number: 6133741
    Abstract: A method for measuring the resistance of a load, preferably the firing pellet of an airbag, that is connected on the secondary side of a rotary transformer, in which the resistance measurement is largely unaffected by the magnetic coupling between the windings of the transformer. According to this method, the capacitor is partially discharged twice in succession. During the first partial discharge, the capacitor is discharged continuously, and during the second partial discharge, the capacitor is discharged in steps. After the two partial discharges, the residual charge voltages at the capacitor are measured and the difference between the two charge voltages is obtained. This difference is an indication of the resistance of the load connected on the secondary side of the transformer.
    Type: Grant
    Filed: October 13, 1998
    Date of Patent: October 17, 2000
    Assignee: Robert Bosch GmbH
    Inventors: Bernhard Mattes, Hartmut Schumacher, Ralf Henne
  • Patent number: 6087836
    Abstract: An apparatus for monitoring the status of the insulation on the wire in a winding in a device comprises a surrogate sample of insulating material having a thickness and properties selected to fail before the failure of the insulation on the wires in the winding, and a detector for detecting and indicating failure of the sample of insulating material. A method of monitoring the status of the insulation on the winding in a dynamoelectric device includes associating a surrogate sample of insulating material with the winding, monitoring the surrogate sample, and providing an alarm when the surrogate sample fails, which is predictive of the failure of the insulation on the winding wire.
    Type: Grant
    Filed: November 18, 1997
    Date of Patent: July 11, 2000
    Assignee: Emerson Electric Co.
    Inventors: Vojislav Divljakovic, Eric J. Wildi
  • Patent number: 5933012
    Abstract: A device for sensing electric discharges in a test object with at least two electric connection conductors comprises transducer equipment and evaluation equipment. The transducer equipment comprises at least one transducer for direction-sensitive sensing of current pulses through the connection conductors by sensing a magnetic field, generated by the current pulses, and the polarity thereof. The transducer delivers a transducer signal to the evaluation equipment in dependence on said current pulses and their direction. The evaluation equipment generates, in dependence on received transducer signals, an indicated signal indicating an electric discharge in the test object.
    Type: Grant
    Filed: May 12, 1997
    Date of Patent: August 3, 1999
    Assignee: ABB Research Ltd.
    Inventors: Tord Bengtsson, Lars-Gunnar Dahlberg, Thomas Eriksson, Akbar Kheirmand, Mats Leijon, Henry Siberg, Dick Rudolfsson, Dag Winkler
  • Patent number: 5923173
    Abstract: A circuit, which can detect a wrong operation of a flyback transformer having a low voltage coil and a high voltage coil, includes a voltage sensing coil which is disposed at the flyback transformer in order to generate a sensed voltage corresponding to a high voltage generated by the high voltage coil. A voltage sensing circuit generates a voltage-sensed signal corresponding to the sensed voltage and provides the voltage-sensed signal to a determination circuit. The determination circuit determines whether the flyback transformer is out of order based on the voltage-sensed signal and the horizontal frequency signal, and generates a determination signal according to the determination result. The shut-down circuit shuts down the flyback transformer in response to the determination signal, thereby preventing the abnormal flyback transformer from generating a dangerously high voltage.
    Type: Grant
    Filed: September 2, 1997
    Date of Patent: July 13, 1999
    Assignee: Daewoo Electronics Co., Ltd.
    Inventor: Kyung-Ho Yu
  • Patent number: 5777468
    Abstract: A variable differential transformer system (10), both linear and rotary (L/RVDT) includes a primary coil (12) drive by a primary drive (20) having a triangle wave generator whose frequency is set by an external frequency control (R.sub.osc and C.sub.osc) which includes compensation for gain temperature error. Secondary coils (14, 16) have a common connection for balanced loading with an input stage arrangement (R7, R8, R9, R10) providing low common mode range and a way to differentiate between normal operation and coil faults detected by a fault detection network (28). Synchronous demodulation (22) extracts both magnitude and direction from the secondary coil signals. Electronic calibration (24) is shown which compensates for sensor offset and gain. Sensor offset calibration is accomplished by adding a percentage of the synchronous demodulation reference wave form to the differential secondary signal.
    Type: Grant
    Filed: December 19, 1996
    Date of Patent: July 7, 1998
    Assignee: Texas Instruments Incorporated
    Inventor: Thomas R. Maher
  • Patent number: 5739693
    Abstract: A method is specified for detecting ground faults on the conductors of an electrical machine, in which method the conductors of the machine are biased with respect to ground by means of an injection voltage (Ui). An optimum utilization of the injection transformer (5) is achieved when the injection signal (Ui) comprises in the transmission period (S) a square-wave signal which switched over periodically between a positive and a negative maximum and has at the start and at the end of the transmission period (S) a quarter-period either of the positive or of the negative maximum.
    Type: Grant
    Filed: September 1, 1994
    Date of Patent: April 14, 1998
    Assignee: Asea Brown Boveri AG
    Inventor: Michael Pfiffner
  • Patent number: 5717338
    Abstract: A method and apparatus for testing flyback transformers counts the number of cycles of a decaying ringing signal generated in a resonant circuit including the secondary winding of the flyback transformer beginning with the second cycle and ending with the cycle where the amplitude of the ringing signal falls below twenty-five percent of the amplitude of the second cycle of the ringing signal.
    Type: Grant
    Filed: November 7, 1995
    Date of Patent: February 10, 1998
    Assignee: Sencore, Inc.
    Inventor: Terry D. Cook
  • Patent number: 5680059
    Abstract: The abnormality detecting method and apparatus for electric equipment measure the frequency spectrum of a signal detected by a partial discharge sensor 9, and detect a partial discharge signal having a frequency component in the neighborhood of a resonance frequency determined on the basis of the electric equipment and its measuring circuit, then detect the abnormality of the electric equipment. In a rotating electric machine particularly, the narrow band filter circuit 23 passes a frequency component around a resonance frequency determined on the basis of the length of the stator core to detect a partial discharge signal from the passed signal.
    Type: Grant
    Filed: December 20, 1994
    Date of Patent: October 21, 1997
    Assignees: The Kansai Electric Power Co., Inc., Mitsubishi Denki Kabushiki Kaisha
    Inventors: Tetsu Shiota, Hideki Tokura, Kenji Morimoto, Takaho Tanaka, Yoshiharu Kaneda, Keiichi Itoh, Ken Kimura, Shigeo Kitamura
  • Patent number: 5663859
    Abstract: An electric device, such as a transformer, has a tank and an arrester for protection against high voltage surges, the arrester being grounded to a wall of the tank. A switch is mounted in the tank wall for enabling the ground connection to be disconnected from outside the tank. The switch includes a shaft extending slidably through an opening in the tank wall. A gripping handle is mounted on an outer end of the shaft, and a spring washer is mounted on an inner end of the shaft. The spring washer is electrically connected to a discharge side of the arrester and is movable toward the wall and into electrically conductive relationship therewith in response to sliding of the shaft. By sliding the shaft in a direction moving the washer away from the wall, the electrical connection is broken. The handle is threadedly mounted to the shaft to be reversible between a first position holding the shaft in its switch closed position, and a second position for enabling the shaft to be slid to its switch open position.
    Type: Grant
    Filed: April 16, 1996
    Date of Patent: September 2, 1997
    Assignee: Cooper Industries, Inc.
    Inventor: Todd Kim Knapp
  • Patent number: 5654644
    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.
    Type: Grant
    Filed: December 20, 1994
    Date of Patent: August 5, 1997
    Assignee: ITT Automotive Europe GmbH
    Inventors: Michael Zydek, Wolfgang Fey, Olaf Zinke
  • Patent number: 5621309
    Abstract: A method of detecting failed disks in power-system surge arresters comprising a network of at least two parallel-coupled stacks of series-coupled ZnO varistors includes measuring differential current flow through each pair of stacks during surge voltage conditions, and comparing the current so measured with a fixed fraction of the total current carried by the arrester. Because each stack contains a like number of substantially identical varistors, current flow through the stack containing a failed disk will measurably exceed current flow through each non-defective stack. If the measured current flow through a stack is excessive relative to current flow through the remaining stacks, the excessive current flow stack is presumed to contain a defective disk. In today's technology, precision Rogowski coils or fiber-optic current sensors provide the high-bandwidth, high dynamic-range transducers necessary for the measurement of both total and differential current.
    Type: Grant
    Filed: February 21, 1996
    Date of Patent: April 15, 1997
    Assignee: Electric Power Research Institute
    Inventor: James M. Feldman
  • Patent number: 5546010
    Abstract: The invention relates to a method for measuring a resistance value in a network incorporated in an electrical apparatus, wherein the network has at least two accessible terminals, the network has at least two time constants differing mutually by at least one order of magnitude, and the resistance value can be related to the voltage applied to the terminal clips and the current flowing through the apparatus.Such control switches are poorly accessible.Direct measurement is time-consuming as a result of the large value of the time constants. These problems are diminished by applying a step-like change of the voltage to the terminal clips, measuring the current flowing through the terminal clips before the change has taken place and after the transient phenomenon related to the smallest time constant and caused by applying the change is damped, and calculating the first resistance value from the measured values of the current.
    Type: Grant
    Filed: January 27, 1995
    Date of Patent: August 13, 1996
    Assignee: N.V. Kema
    Inventor: Henricus F. A. Verhaart
  • Patent number: 5530366
    Abstract: An apparatus for detecting a partial discharge in a high voltage transformer comprising a live tank comprises a metal box detachably connected to the tank; a first acoustic sensor inside the box for converting acoustic waves in a first frequency band to a first electrical output signal; signal conditioning circuitry inside the box for amplifying and filtering the first electrical signal; an electrical to optical converter, inside the box, for converting the amplified and filtered electrical signal to an optical signal; a fiber optic link for carrying the optical signal to a location remote from the transformer; and an optical to electrical converter at the remote location for converting the optical signal to a second electrical signal, the second electrical signal being indicative of a partial discharge inside the tank. The second electrical signal may be fed to an oscilloscope or recording equipment for determination of the occurrence of a partial discharge.
    Type: Grant
    Filed: November 1, 1994
    Date of Patent: June 25, 1996
    Assignee: ABB Power T&D Company Inc.
    Inventor: Chaoukat N. Nasrallah
  • Patent number: 5506511
    Abstract: A method for determining transient partial discharges in the insulating medium of an electrical power transformer, for example, oil and paper, uses in one embodiment a circular plate inserted in the interior of a transformer tank which picks up partial discharge signals. These are high frequency transients which are processed by use of DC notch filters, blocking capacitors and amplified by high frequency amplifiers. The peaks of the partial discharge signal are detected by peak amplifiers, sorted by relative magnitudes, and either displayed or further processed by computer techniques for indicating incipient transformer failure.
    Type: Grant
    Filed: September 9, 1994
    Date of Patent: April 9, 1996
    Assignee: Electric Power Research Institute Inc.
    Inventors: Stig L. Nilsson, William B. Gish
  • Patent number: 5500598
    Abstract: The apparatus comprises a plurality of connectors (9, 10, 11, 12 . . .) for connecting to the component to be tested (e.g. a transformer), a signal generator (19), a measuring system (23) and control means (22) which is arranged to control which of the connectors (9, 10, 11, 12 . . .) are connected to the signal generator (19) and the measuring system {23) and arranged to control the function of the signal generator (19) and the measuring system (23) so that the same signal generator (19) and measuring system (23) can be used to carry out a variety of different tests on the component, the signal generator (19) also being arranged to provide a synchronising signal (28) to the measuring system (23) so that the phase relationship between measurements at different times can be calculated by comparing the phase relationships of those measurements with the synchronising signal (28).
    Type: Grant
    Filed: July 27, 1994
    Date of Patent: March 19, 1996
    Assignee: Voltech Instruments Limited
    Inventor: John S. Ford
  • Patent number: 5455506
    Abstract: A method and an apparatus are provided for safely testing an autotransformer of power distribution lines which has an identified centre tap ground connector, a primary winding terminal and a secondary winding terminal. The method for safely testing the autotransformer includes the steps of disconnecting the terminals and connector of the autotransformer from the distribution lines, applying a first testing AC voltage having a maximum value of substantially one volt only between a first of the terminals and the ground connector, measuring a first value of an AC voltage between the first terminal and the ground connector, and measuring a second value of an AC voltage between the second of the terminals and the ground connector.
    Type: Grant
    Filed: July 21, 1994
    Date of Patent: October 3, 1995
    Assignee: Copek Electro Ltee
    Inventors: Yvan Mimeault, Jacques Kirouac, Yves Tremblay, Roland Caron
  • Patent number: 5396172
    Abstract: A transformer fault analyzer provides on site fault analysis of electrical distribution transformers, relying on patterns of parameter variation in transformer winding ratios, winding resistance and magnetizing impedance, and comparison of these parameters to predetermined values. In a preferred embodiment the analysis considers transformer ratio balance and magnetizing impedance balance. The transformer analyzer may be used with the transformer under load or no load conditions, and thus can be used to test transformers in the field as well as surplus or refurbished transformers.
    Type: Grant
    Filed: July 20, 1993
    Date of Patent: March 7, 1995
    Assignee: Ontario Hydro
    Inventors: Michael V. Lat, Thomas A. Gough
  • Patent number: 5386193
    Abstract: A partial discharge detecting device for a resin-molded transformer having no-load switching tap terminals on a high voltage winding thereof. An amplifier amplifies the output detection signal of a partial discharge detecting sensor connected between the tap terminals, and an electro-optic converter converts the output signal of the amplifier into an optical signal. The optical signal is applied through an optical fiber to an opto-electric converter where it is converted into an electrical signal. The electrical signal is applied to an indicator. The partial discharge detecting sensor, the amplifier circuit, and the electro-optic converter are held at a potential corresponding to a potential of the tap terminals.
    Type: Grant
    Filed: May 19, 1993
    Date of Patent: January 31, 1995
    Assignee: Fuji Electric Co., Ltd.
    Inventors: Takao Maeda, Tatsuo Nishizawa, Kenji Watanabe
  • Patent number: 5365177
    Abstract: An apparatus for providing a quantitative measurement of high frequency corona discharges from electrical devices operating at high voltages, including an alternating current power source for providing a test signal variable in amplitude and frequency, a high pass filter to reject power source cyclical components and to isolate corona discharge components, an adjustable gain amplifier, and a power meter providing a quantitative readout of the amplitude of corona discharges integrated over a preselected time period. Electromagnetic shielding of individual assemblies comprising the test equipment allows corona detection without emissions or interference from external sources.
    Type: Grant
    Filed: March 10, 1993
    Date of Patent: November 15, 1994
    Assignee: Honeywell Inc.
    Inventors: Charles H. Hamp, III, David D. Maine
  • Patent number: 5276402
    Abstract: Three-phase transformer testing method and system enabling convenient performance of ANSI-required checking of polarity and phase-relation and also enabling measurements of core loss, load loss and transformer ratio to be performed conveniently. Only a total of six test leads are needed, being connected one each to three high-voltage transformer terminals H1, H2 and H3 and being connected one each to three low-voltage terminals X1, X2 and X3. Since only six test leads are needed, it is easy to arrange them and to connect them without confusion to the six transformer terminals.
    Type: Grant
    Filed: February 28, 1992
    Date of Patent: January 4, 1994
    Assignee: Hipotronics, Inc.
    Inventor: Donald M. Schucht
  • Patent number: 5264799
    Abstract: A rotatable circular platform is used for automatically testing power transformers. The rotatable circular platform is provided with a plurality of carrier tracks equally spaced around the periphery of the rotatable circular platform; each one of the carrier tracks is adapted to carry a power transformer to be tested and is provided with a corresponding connecting post having a pair of connecting contact points. Around the outer periphery is a plurality of stationary posts, each one of which has a pair of stationary contact points to allow a sliding engagement with the connecting contact points of the connecting posts. Each pair of the stationary contacts is electrically connected to a test instrument to test the performances of power transformers, while each pair of the connecting contact points is provided with a pair of clamps to clamp onto the test terminals of a power transformer loaded on a corresponding carrier track.
    Type: Grant
    Filed: July 16, 1992
    Date of Patent: November 23, 1993
    Assignee: San Horng Electric Factory Co., Ltd.
    Inventors: Yincheng Huang, Yiing H. Hwang, Ying Y. Huang
  • Patent number: 5233305
    Abstract: Typically, in a partial discharge detecting device for a resin-molded transformer with tap terminals of a no-load switching type on the high voltage winding, the output signal of a partial discharge detecting sensor connected between the tap terminals is applied through an amplifier circuit to an indicator. The sensor is arranged on the high potential side whose potential corresponds to the potential to ground of the tap terminals. This construction contributes to detection of void coronas formed in the transformer with high accuracy.
    Type: Grant
    Filed: January 23, 1992
    Date of Patent: August 3, 1993
    Assignee: Fuji Electric Co., Ltd.
    Inventors: Tatsuo Nishizawa, Takao Maeda, Hiroshi Moriya
  • Patent number: 5200737
    Abstract: A system and method for detecting partial discharge of gas-insulated switchgear wherein a high-frequency component and the fundamental wave component of the voltage applied to the conductor of the gas-insulated switchgear are detected, the zero-cross point of the fundamental wave component is set as the starting point for the voltage, and the presence of partial discharge and the reason for the occurrence of partial discharge are ascertained based on the phase difference between the phase of the detected high-frequency component and the phase of the starting point of the voltage.
    Type: Grant
    Filed: November 29, 1991
    Date of Patent: April 6, 1993
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Katsumi Konishi, Takaaki Sakakibara
  • Patent number: 5172067
    Abstract: Apparatus for testing a high voltage inductive coil such as a transformer winding applies a DC voltage to the coil and measures coil voltage and current from which its resistance can be calculated. A load resistor in a discharge circuit dissipates energy stored in the coil prior to test apparatus removal to reduce arcing for operator safety. Diode bridges in the discharge circuit provide a nonlinear resistance which increases with decreasing voltage and current to ensure rapid and complete discharge of the energy stored in the coil's magnetic field. A three position make-before-break switch includes first and third positions for respectively coupling the DC supply and the discharge circuit to the coil and an intermediate position for simultaneously coupling the DC supply and the discharge circuit to the coil for safely initiating coil discharge.
    Type: Grant
    Filed: May 20, 1991
    Date of Patent: December 15, 1992
    Assignee: Commonwealth Edison Company
    Inventor: Willard G. Hoffmann
  • Patent number: 5159319
    Abstract: A faulted circuit detector having an electrically isolated and remotely positioned indicator detects fault currents in a monitored conductor. When a fault of a predetermined magnitude is detected, a light pulse is transmitted from the detector to the indicator via a fiber optic cable where, upon receipt, the pulse is converted to an electrical pulse causing the indicator to indicate a "fault" state. A reset circuit within the indicator resets the indicator at regular intervals to the "normal" state as long as a predetermined minimum voltage is present on the monitored conductor. A test circuit is also provided to allow service personnel to field test the device with the monitored conductor in an energized state.
    Type: Grant
    Filed: June 25, 1990
    Date of Patent: October 27, 1992
    Assignee: Cooper Industries, Inc.
    Inventors: Michael P. Dunk, Gary D. Rector, John F. Banting
  • Patent number: 5111149
    Abstract: Method and apparatus for automatically testing an electrical coil through a surge tester. Comparison to a stored waveform through error area ratio computation is achieved by use of digital computer data processing techniques. A uniform threshold of acceptability is disclosed which is not dependent on voltage or type of coil tested. Statistical analysis may be programmed or hardwired into an embodiment to yield easily discernable manufacturing or field test information. Optimization of the entire process and the testing steps may also be achieved through an apparatus which may provide a variety of different output possibilities and which may be customized to the user's situation. Update and storage of test results is included as well as correlation with manufacturing data.
    Type: Grant
    Filed: February 28, 1989
    Date of Patent: May 5, 1992
    Assignee: Baker Electrical Instrument Company
    Inventor: Jeffrey D. Lebesch
  • Patent number: 5087885
    Abstract: A portable tester is disclosed for determining in the field the condition of a lightning arrester connected in parallel with a high voltage winding of a transformer. The tester comprises a battery; an inverter connected to the battery for generating an AC output; at least one transformer and a rectifier for transforming the output of the inverter to a high voltage DC having a magnitude greater than the breakdown voltage of a lightning arrester connected in paralled to the high voltage winding of a transformer being tested; at least one capacitor connected across the rectifier for being charged to the high voltage DC; an overvoltage spark gap switch for discharging the high voltage charge of the capacitor across the high voltage winding of the transformer being tested; and a storage oscilloscope for detecting the response of the winding to the high voltage pulse. A normally functioning lightning arrester will clamp the voltage across the transformer winding at the arrester's known breakdown point.
    Type: Grant
    Filed: April 16, 1990
    Date of Patent: February 11, 1992
    Assignee: Electron Instruments
    Inventor: Russell N. Bergstrom
  • Patent number: 5075629
    Abstract: A partial discharge detecting device for transformers includes an antenna disposed in a metallic insulation gas filled tank enclosing a core and coil assembly and a signal processing circuit for processing an output signal from the antenna. The antenna includes a magnetic core and a single coil or two coils differently operated. An electromagnetic wave due to the partial discharge is detected by the antenna. A detection signal from the antenna is supplied to the signal processing circuit, which determines whether or not the partial discharge has taken place, based on the detection signal.
    Type: Grant
    Filed: January 24, 1990
    Date of Patent: December 24, 1991
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Tokihiro Umemura, Keiichi Abe
  • Patent number: 4975649
    Abstract: A method and apparatus for detecting the loss of regulation in ferroresonant transformer is disclosed. The flux in the magnetic shunts is sensed by a winding. The resulting signal is differentiated. If the differentiated signal contains pulses, regulation is present, if no pulses are found the transformer is not in regulation.
    Type: Grant
    Filed: December 18, 1989
    Date of Patent: December 4, 1990
    Assignee: Albar, Inc.
    Inventor: Howard H. Bobry
  • Patent number: 4916402
    Abstract: An apparatus for detecting direct current magnetic flux deflection of an electrical transformer comprising a magnetic detector for generating an output voltage waveform, an integrator connected to the magnetic detector for integrating the output voltage waveform from the magnetic detector. Positive and negative peak value detectors are connected to the integrator for detecting positive and negative peak values of the output voltage waveform integrated by the integrator. A comparator connected to the positive and the negative peak value detectors compares the positive and the negative peak values to provide a peak difference.
    Type: Grant
    Filed: September 20, 1988
    Date of Patent: April 10, 1990
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Toyokazu Kouan, Katsumi Shiono
  • Patent number: 4904945
    Abstract: An apparatus for detecting direct current magnetic flux deflection of an electrical transformer comprising a magnetic detector for generating an output voltage waveform and Fourier series developer connected to the magnetic detector for developing the output voltage waveform from the magnetic detector into a Fourier series. An even number harmonic detector is connected to the Fourier series developer for detecting an even number harmonic in the Fourier series, thereby determining the presence of a direct current magnetic flux deflection. A process for detecting direct current magnetic flux deflection is also disclosed.
    Type: Grant
    Filed: September 20, 1988
    Date of Patent: February 27, 1990
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Toyokazu Kouan, Katsumi Shiono
  • Patent number: 4878026
    Abstract: The measuring circuit comprises an integrator to which a signal representative of the current flowing through the primary winding of the output transformer of an inverter is applied. The integrator output signal is reset at the beginning of each period of the A.C. component of said current and is applied to a sample and hold stage whose output signal represents the integrator output signal just before it is reset. An intermediate stage is arranged between the integrator and the sample and hold stage to reduce the influence of load impacts by limiting the maximum possible variation of the output signal during the sampling period.
    Type: Grant
    Filed: December 28, 1987
    Date of Patent: October 31, 1989
    Assignee: Merlin Gerin
    Inventors: Philippe Moreau, Jean-Noel Fiorina
  • Patent number: 4873489
    Abstract: The density of charge entrained in fluids such as oils in transformer systems, capacitors, cables, pumps and fuel transfer systems is measured by introducing the oil into a conductive container which expands in volume to receive the fluid without expelling any fluid. The container is shielded by a grounded conductor which prevents inducement of charge on the container by external sources. By measuring the current between the conducting expandable container and the surrounding shield and accounting for the effects of the charge induced on the outer wall of the container by its own induced voltage, the net charge entrained in the fluid as it is brought into the container is deduced. Extraneous effects of conduction and electrokinetic currents are automatically excluded from the measurement. The oil is then automatically returned to the transformer system by the contraction of the conductive container so that the measurement can be repeated without accumulating an inventory of fluid.
    Type: Grant
    Filed: March 2, 1988
    Date of Patent: October 10, 1989
    Assignee: Massachusetts Institute of Technology
    Inventors: James R. Melcher, Alfred J. Morin, II, Markus Zahn
  • Patent number: 4868509
    Abstract: A method and apparatus for detecting system failure in a magnetron power supply circuit. The apparatus is capable of providing an indication as to whether it is the power supply or the magnetron which has failed. A dual half wave doubler power supply circuit is provided and the currents corresponding to the respective dual portions are measured. The currents are compared to detect a failure of one of the dual power supply circuits while a sum of the currents may detect a failure of the magnetron.
    Type: Grant
    Filed: May 23, 1988
    Date of Patent: September 19, 1989
    Assignee: Fusion Systems Corporation
    Inventors: Michael G. Ury, William J. Jones
  • Patent number: 4857856
    Abstract: A method of testing transformers and other inductive devices comprises monitoring displacement of a conductor in a winding by injecting a high frequency alternating signal into the conductor while a supply-frequency alternating current is flowing in the conductor and subsequently observing the modulation of the high frequency signal resulting from displacement of the conductor. The high frequency signal has a frequency in the region of the resonance frequency of stray capacitances and inductances exhibited by the winding of which the conductor forms a part. Both the magnitude and the frequency response of the modulation of the high frequency signal may be monitored to determine parameters relating to the displacement of the conductor.
    Type: Grant
    Filed: February 16, 1988
    Date of Patent: August 15, 1989
    Assignee: ERA Patents Limited
    Inventors: Raymond L. Coleman, Peter A. Kurn
  • Patent number: 4851766
    Abstract: A fault diagnosis system for a rotor winding of rotary electric machines is disclosed, in which the rotor winding of rotary field type is excited in DC fashion by an excitation circuit, on which an AC voltage is superposed, the impedance of the rotor winding is calculated from the current and voltage of the AC portion flowing in the rotor winding, and the resulting impedance is compared with a reference impedance thereby to decide a fault, if any, of the rotor winding, thus making possible accurate diagnosis of a rotary electric machine even while it is running.
    Type: Grant
    Filed: December 9, 1987
    Date of Patent: July 25, 1989
    Assignee: Hitachi, Ltd.
    Inventors: Ryoichi Shiobara, Masao Ohi
  • Patent number: 4833398
    Abstract: An electric testing system to be attached to a water heater to permit instantaneous testing of the operability of each heating element comprising a separate branch circuit including each heating element and a current flow detecting device.
    Type: Grant
    Filed: October 12, 1988
    Date of Patent: May 23, 1989
    Inventor: Robert E. Buchan
  • Patent number: 4737775
    Abstract: The apparatus for monitoring an insulation deterioration of an insulation layer surrounding an outer surface of a coil conductor comprises a semiconductor layer of 10.sup.2 to 10.sup.7 ohm-cm formed within the insulation layer of the coil, an electric field sensor such as Pockels element or ferroelectric element mounted on the coil insulation layer. The semiconductor layer is so formed as to divide the insulation layer into inner and outer layers. When the inner layer deteriorates, a high electric field is sensed, while the outer layer deteriorates, a low electric field is sensed. Therefore, it is possible to discriminate the insulation deterioration positions on the basis of the change in electric field detected by the sensor element. In case of deterioration, alarms are produced or the power supply of machine is turned off for safety.
    Type: Grant
    Filed: December 9, 1985
    Date of Patent: April 12, 1988
    Assignee: Kabushiki Kaisha Meidensha
    Inventors: Takao Tokuda, Hisashi Suwahara, Yasuaki Nozu