Abstract: In wire processing systems and methods, a wire channel receives a wire. One or more fluid guides flow the fluid into the wire channel to move, along the wire, a component (e.g. a solder sleeve) positioned at least partially in the wire channel and coupled to the wire. Other features are also provided.

Abstract: A first surge absorber has a low resistance when a surge voltage which is greater than or equal to a first operating voltage is applied to a power supply line, and has a high resistance when the surge voltage which is greater than or equal to the first operating voltage is not applied. A detector outputs a detection signal indicating that the surge voltage is greater than or equal to the first operating voltage when the surge voltage is greater than or equal to the first operating voltage. A second surge absorber becomes a low resistance when a surge voltage greater than or equal to a second operating voltage is applied, and becomes a high resistance when a surge voltage greater than or equal to the second operating voltage is not applied.

Abstract: Exemplary embodiments are directed towards safety systems associated with ultra-fast fault signal pulses to increase the fault signal pulses from milliseconds to seconds to energize external devices (e.g., LED lights). This is turn will alert the operators that the system is operational or a fault was detected. The fault signal width pulses are extended to drive or trigger external devices, such as external relays, which in turn completes a circuit to energize any external devices.

Abstract: There is described an electrical energy conversion system comprising: at least a first inverter (1) and at least a second inverter (2), whose outputs are connected in parallel; at least a first DC voltage source (PV1) connected to the input of the first inverter (1) and a second DC voltage source (PV2) connected to the input of the second inverter (2); a ground connection of the first inverter (1) and a ground connection of the second inverter (2). The ground connection of said inverters comprises a ground connection branch (1G; 2G) with a current sensor (5/1; 5/2) which supplies a signal proportional to a leakage grounding current (Ileak) measured in said ground connection branch (1G; 2G). Through the signal proportional to the leakage current measured a feedback signal is generated to control the leakage current (Ileak).

Abstract: A sensor apparatus for detecting leakage current in a suspension-type insulator of an electrical power system is disclosed. The sensor apparatus includes a housing having a leakage current sensor contained therein, a door pivotally connected to the housing and adapted to move between an open position where a grounded end fitting of the insulator is received by the sensor apparatus and a closed position, and a clamping mechanism connected to the housing. The leakage current sensor is adapted to detect a leakage current along the insulator. The clamping mechanism is adapted to clamp the sensor apparatus to the grounded end fitting of the insulator.

Abstract: This invention relates to a method of and system for monitoring shaft signals associated with a shaft of a rotating machine. The method comprising receiving voltage signals associated with the shaft; receiving current signals associated with the shaft; determining, from the received voltage and current signals, voltage and current data relating to the machine; presenting at least some of the determined voltage and current data to a user; trending at least the determined voltage data to at least determine voltage data trends associated with the machine; and determining from the voltage and current data if a fault condition has occurred and generating an alarm signal or condition in response thereto.

Abstract: A measuring device for measuring insulation resistance of an electric vehicle includes a measuring unit, a voltage detecting unit, and a control unit. The measuring unit includes a first tap, a second tap, a switch, and a measuring resistor. The first tap is to be electrically coupled to a high potential side of a high voltage system. The second tap is to be electrically coupled to a ground side of a low voltage system. The switch and the measuring resistor are connected in series between the first tap and the second tap. The voltage detecting unit is for detecting a voltage formed between the first tap and the second tap. The control unit is operable for controlling ON and OFF states of the switch, and is configured to determine the high potential insulation resistance and the low potential insulation resistance after operating the switch in the ON and OFF states.

Abstract: An instrument (1) and a method for measuring pulses of partial electrical discharges in an electrical system comprise data processing means (5) operatively associated both with an input stage (2), able to receive an analogue signal (3) representing said pulses and to provide a digital representation of the entire wave form of the pulses, to receive said digital representation, extract the value of predetermined parameters relating to the wave form of the pulses and transfer to and output stage (4) a processed digital signal comprising said values, the processing means (5) being able to operate substantially in real time, i.e. with no need for a memory for the intermediate storage of the data.

Abstract: A power equipment includes a first internal abnormality detection apparatus comprising a first antenna accommodation pipe which is connected to a first connection pipe formed in a enclosed container and which accommodates a first antenna therein, and a first signal detection circuit which is connected to a first antenna and which detects an electromagnetic wave signal emitted when any abnormality has occurred within the enclosed container.

Abstract: A portable partial discharge detection apparatus and method thereof are provided. The portable partial discharge detection apparatus includes a detection unit, a control unit and an alarm unit. The detection unit is for detecting a signal generated by an apparatus under tested due to insulation degradation. The control unit is for diagnosing whether the signal is partially discharging and outputting a diagnosis result of partial discharge according to the number of partially discharging per unit of time. The alarm unit is for automatically notifying the diagnosis result of partial discharge.

Abstract: Disclosed is a portable electronic device, including: an interface unit connected to an external device; a housing provided with the interface unit; a cap placed in a location allowing for the covering of the interface unit and covering the interface unit when attached to the housing; a signal detecting line placed in the interface unit and connected to a predetermined electric potential when the external device is connected to the interface unit; a switch which electrically connects the signal detecting line to the predetermined electric potential when the cap is attached to the housing and electrically disconnects the signal detecting line from the predetermined electric potential when the cap is separated from the housing; and a control unit connected to the interface unit and configured to determine whether the signal detecting line is electrically connected to the predetermined electric potential or not.

Abstract: A bearing failure detection system includes a thermal protector switch circuit having a wear strip located within an interior of a motor stator. In response to bearing failure or wear above a predetermined magnitude, the motor rotor will shift off its axis of rotation and wear away the wear strip or break the electrically conducting material of the wear strip and activate the stator thermal protector switch circuit and shut down the electric motor. The wear strips assist the thermal protector switch circuit in the identification of a bearing failure and the light rubbing that results therefrom prior to the generation of an electrical burning smell that may otherwise occur after a prolonged period of rubbing.

Abstract: An apparatus and method for at least one of detecting and preventing burning of a PCB is disclosed. The method includes configuring a first comb array defined by a plurality of first fingers at a first potential; configuring a second comb array defined by a plurality of second fingers at a second potential different from the first potential; interlacing the plurality of first fingers defining the first comb array with the plurality of second fingers defining the second comb array embedded in a substrate; disposing the substrate with the PCB; and detecting a rise in leakage current between the first and second comb arrays indicative of a breakdown of the substrate.

Abstract: A container is provided. The container includes a casing having an opening for admitting contents into the container. A matrix of conductive lines extends across at least a portion of the casing. A sensor senses a breach of integrity of the matrix. An indicator indicates a breach of integrity of the container when the sensor senses a breach of integrity of the matrix. A system is also provided. The system includes a monitoring network and a container. The container includes a casing having an opening for admitting contents into the container. A matrix of conductive lines extends across at least a portion of the casing. A sensor senses a breach of integrity of the matrix. An interface transmits a signal to the monitoring network when the sensor senses a breach of integrity of the matrix, the signal indicating a breach of integrity of the container.

Abstract: A method of detecting a state of an insulation resistance fall detector that includes: a detection resistance connected in series to an insulation resistance between a vehicle body and a power source; a condenser provided between the insulation resistance and the detection resistance; a pulse signal applying unit that applies a pulse signal to a serial circuit constituted by the insulation resistance, the condenser and the detection resistance; a low pass filter that filters a voltage of a connecting point between the coupling condenser and the detection resistance; and a fall detecting unit that detects a fall of the insulation resistance on the basis of the output of the filter, the method comprising the steps of: varying a pulse width of the pulse signal; and detecting the state of the insulation resistance fall detector on the basis of the output of the filter when the pulse width is varied.

Abstract: An insulation resistance drop detector 50 and a method of detecting a state of malfunction of the detector 50 are provided. When open of a coupling capacitor Co or malfunction of a lowpass filter 53 is occurred, a time constant of the low pass filter 53 is decreased and a rising time of an output of the lowpass filter 53 against an output of a pulse signal P1 becomes shorter than that in a state of normal. Thereby, malfunction of the detector 50 can be detected based on the output of the filter 53 corresponding to change of frequency of the pulse signal P1.

Abstract: A method of detecting the improper mounting of a sensor on a motor vehicle includes monitoring the output signals of the sensor, determining the noise levels in the output signals, and comparing the noise levels from the output signals to a threshold noise value to determine if the sensor is properly mounted. Preferably, the method monitors the output signals of a first sensor and a second sensor, determines the noise levels in the output signals being emitted by each of the sensors, and compares the noise levels of the first sensor to the noise levels of the second sensor to determine if the sensors are properly mounted.

Abstract: A monitoring system includes at least one partial discharge (PD) sensor. The PD sensor is configured to monitor a component of an aircraft wiring system and to acquire a monitoring signal. A method embodiment for monitoring an aircraft wiring system includes acquiring a number of monitoring signals for a number of components of the aircraft wiring system using a number of partial discharge PD sensors. The method further includes conveying the monitoring signals from at least one of the PD sensors to a data acquisition system.

Abstract: A portable partial discharge detecting device for measuring partial discharge in energized electrical systems encloses a relay circuit and a DC power source. A pair of sensor circuits are enclosed within electrically coupling clamping mechanisms and are coupled to the relay circuit at sensor inputs by cabling. The clamping mechanisms engage the ground leads of the electrical system. Trip and alarm networks of the relay circuit continuously compare the picocoulomb values of the partial discharge pulses against user set threshold values. Relays coupled to the trip and alarm networks respond if the threshold values are exceeded. The alarm setting is always set to a pick-up value equal to or less than the trip setting. The trip network relays are coupled to a control circuit of the electrical system and can take the system off-line. The alarm network relays are coupled to an alarm circuit and can warn the user that a certain level of partial discharge has been reached within the electrical system.

Abstract: A manipulating protective glove structure for use with non-conductive, hazardous materials, or materials sensitive to contamination, in a sealed environment, e.g., glove box. The glove structure embodies components which provide monitoring and signaling to the user, of a breach, in the glove structure. The outer surface of the manipulating glove itself is made electrically conductive by conductivity treatment of by inserting the glove into a thin conductive glove member which is sized to tightly cover the outer surface of the manipulating glove. An isolated electrical wire is electrically mounted to a the conductive outer surface with prevention of ingreee of air (with possible contamination). An electrical monitoring device is electrically connected to the user's skin and to the outer conductive layer via the electrical wire.

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: There are two coaxial cable test instruments, of which a primary instrument provides a rump circuit having a battery, a first electric signal device and two probes in series-connection with each other, of which the probes are in the form of the central conductor and surrounding shield parts of a typical coaxial cable connector. The other or secondary instrument provides a second electric signal device which is connected with two further probes in the form of the central conductor and surrounding shield parts of another coaxial cable connector. To test a cable component for a short-circuit, the primary instrument is connected with one of the end connectors of the cable. If the first signal device, for instance a light bulb, then lights up on closure of the rump circuit via the short-circuit bridge between the central conductor and surrounding shield of the cable, the lighted bulb will clearly indicate the short circuit in the cable.

Abstract: An electrical isolation device for use in an electrical distribution network having a plurality of branch circuits each defined by line and neutral conductors connected between a power source and a load, the line conductor being electrically connected to one of a plurality of line buses at an electrical distribution panelboard, the neutral conductor being electrically connected to a neutral bus at the electrical distribution panelboard. The isolation device includes a filter coupled between a selected number of line buses and the neutral bus at the panelboard and is designed to provide a low impedance path for an arcing fault occurring on either of the selected number of line buses. In another embodiment, the isolation device is comprised of a filter coupled between the line and neutral conductor of a selected one of the branch circuits and is designed to provide a low impedance path for an arcing fault occurring on the line conductor of the selected branch circuit.

Abstract: Prior to beginning a dielectric withstand (leakage current) or insulative impedance test, but after applying the high voltage that will be used in the test, the temporary charging currents resulting from application of the high voltage are measured and analyzed to determine if the test sample is properly connected to the test apparatus. If no charging currents are measured, or if the insulation resistance is too high, then it is determined that the test sample is not properly connected and the test is terminated.

Abstract: A device suitable for testing the integrity of insulation coating an electrosurgical instrument is described. The device includes a test sleeve and a fault detection unit. The test sleeve is generally tubular and defines an open bore with a resilient conductive lining mounted therein. The fault detection unit is coupled to the conductive lining such that establishment of an erroneous current path between the conductive lining and an electrosurgical device is detected.

Abstract: A remote contamination sensing device for contamination on insulation of electric power lines and substations includes a data logger and a supporting structure to which a sensing capacitor with at least two conductors is attached such that the conductors are spaced apart and insulated from each other. A capacitance measuring device, for measuring capacitance data between the conductors, is connected to the data logger. A hygrometer, for measuring the relative humidity of the ambient air, is also connected to the data logger. A first temperature sensor, for measuring the ambient temperature, and a second temperature sensor, for measuring the surface temperature of the capacitance sensor, are connected to the data logger. The measured capacitance data, relative humidity data, ambient temperature data, and surface temperature data are stored in the data logger.

Abstract: A load insulator 2, for interposition into a loaded line, comprises a plurality of mechanical links 4 connected together to form a chain, and an electrical insulator 8 arranged between a pair of adjacent interlocked links 10,12 in the form of an insert of insulative material to electrically isolate the links 10,12 of the pair from each other. A load sensing device may be provided for sensing the strain on the mechanical link. A measuring device 24 for measuring the resistance of the insulator 8 is provided to check the electrical condition of the load insulator, whilst a recording and indicating device allows for recording of electrical strikes and provide a lifetime expiry indicator.

Abstract: A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems and capacitive insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit that modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. The sensor detects changes in the charging current through the insulation ground conductor, indicating the degradation of the dielectric properties between the foil layers. The sensor and associated electronic circuitry are enclosed in a housing adaptable to be used with a capacitance tap common to high voltage measurement and control apparatus.

Abstract: A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems and capacitive insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit such that it modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. The sensor detects changes in the charging current through the insulation ground conductor, indicating the degradation of the dielectric properties between the foil layers. The sensor and associated electronic circuitry are enclosed in a housing adaptable to be used with a capacitance tap common to high voltage measurement and control apparatus.

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.

Abstract: To carry out a non-destructive test for testing insulation of a small-size electric machine having a coil, a surge voltage is applied to the coil of the electric machine mounted in a decompression tank whose inner pressure is kept from 15 to 25 [Torr] so as to generate glow discharge in case there exists a flaw in the coil.

Abstract: A load insulator 2, for interposition into a loaded line, comprises a plurality of mechanical links 4 connected together to form a chain, and an electrical insulator 8 arranged between a pair of adjacent interlocked links 10,12 in the form of an insert of insulative material to electrically isolate the links 10,12 of the pair from each other. A load sensing device may be provided for sensing the strain on the mechanical link. A measuring device 24 for measuring the resistance of the insulator 8 is provided to check the electrical condition of the load insulator, whilst a recording and indicating device allows for recording of electrical strikes and provide a lifetime expiry indicator.

Abstract: A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit such that it modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. Alarm level thresholds and alarm time delay are embodied in a control device which may be located in a remote location, away from the high voltage equipment. Step-graded insulation systems form a capacitively divided circuit between the high potential and ground. As the dielectric between the foil layers breaks down, the total capacitance of the insulation system increases, producing an increase in the charging current.

Abstract: A device for testing for leakage of electronic equipment has a female AC connector for receiving the male AC connector of the electronic equipment to be tested and a male AC connector for attaching the test device to a source of AC power. The device also includes an electrically conductive probe and a meter for detecting a voltage on a surface contacted by the probe. Within the device are first and second switches which connect the male AC connector and the female AC connector in four successive configurations for applying AC power to the connector of the piece of equipment to be tested. A sequencing circuit in the device operates the two switches to apply all four test configurations within an interval of 1.033 seconds. The probe and the meter for detecting a current in the probe is used to contact the conductive surfaces of the piece of equipment being tested to detect a voltage while the four tests are applied to the power connector.

Abstract: A portable early warning device for use in detection of breaches in protective garments such as gloves, during surgical procedures and the like. The device embodies a central process and source unit containing sensing wave generator, indicators, driving circuitry, digital analyzing and monitoring circuitry and a power source. The central process and source unit is separately directly connected to the object, e.g. skin of the patient, and to the device carrier, e.g. skin of the surgeon, via standard wires and EKG type terminal connectors. A conductive breach of protective garments such as surgical gloves with in vivo patient fluids, such as blood (of a possibly hazardous nature), completes a circuit and triggers a warning (either visible, audible, or mechanical) of the breach.

Abstract: In an apparatus for testing cable (comprising a metallic core jacketed by insulation) to detect localized defects on the insulation caused by its carbonization, the cable is moved in an axial path through an array of five ring electrodes radially spaced from that path and spaced from each other along the path by axial gaps. The first and fifth electrodes from left to right are grounded while high voltage circuits supply current to the middle three electrodes at DC voltages which causes (a) the second and fourth electrode, and (b) the third electrode to be positive and negative, respectively, relative to ground, and which voltages are high enough to produce flow of charge through the atmosphere adjacent the electrodes, and between the electrodes and the moving cable.

Abstract: A diagnostic measuring system (20) for gas insulated electrical substations having UHF couplers (11) fitted to bus chambers (12) monitors for partial discharge events within the chamber (12) to identify the nature and location of an emergent breakdown condition. The system (20) identifies each partial discharge event but characterizes it by amplitude and its time of occurrence with respect to the start of the 50 Hz power frequency wave. The characterized events are communicated over an optical fiber link (13) configured as a token passing ring to an analyzer (25) where a comparison is made with stored historic data characterizing known events. The analyzer (25) provides a self checking routine for the system (20). A microprocessor (36) forming part of a unit (21) associated with a plurality of couplers (11) provides data compression of events identified from these couplers.

Abstract: A system for detecting arcing faults in DC electrical cable power distribution circuits, typically in telecommunications networks, monitors the power spectrum of distribution lines over a frequency band of about 4 Hz to 5 KHz in which current surges characteristic of arcing line faults have been found to occur. The system compares power levels in this detection band with a threshold level typical of normal communications traffic and registers an alarm condition when an excess indicative of arcing is detected.

Abstract: A fault indicator for a surge arrester includes an explosive cartridge which is detonated by a fault condition of an attached surge arrester to remove a covering which exposes colored, reflective tape to provide a visual indication of the faulted condition of the surge arrester.

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: The processing circuit of the insulation monitor comprises a microprocessor receiving on a first input a signal representative of the DC component, or the component of preset frequency different from the frequency of the mains system to be monitored, of the voltage applied to the insulation monitor terminals. The microprocessor receives on a second input a signal obtained by making the difference between a measured voltage representative of said voltage component and a preset threshold value and by multiplying this difference by a multiplication coefficient. When the measured voltage is greater than the threshold value, the microprocessor uses the signal applied to the second input so as to improve the precision in the higher voltage range.

Abstract: A portable generator generates a predetermined signal and has an output connected to a first transducer for transmitting the above signal to the body of a first operator (e.g. physician, nurse, etc.); and processing means for analyzing a signal picked up by a second transducer on a second operator (e.g. a patient, etc.) and detecting the significant presence of the above predetermined signal, as a consequence, for example, of direct or indirect contact between the first operator and the second operator.

Abstract: A portable generator generates a predetermined signal and has an output connected to a first transducer for transmitting the above signal to the body of a first operator (e.g. physician, nurse, etc.); and processing means for analyzing a signal picked up by a second transducer on a second operator (e.g. a patient, etc.) and detecting the significant presence of the above predetermined signal, as a consequence, for example, of direct or indirect contact between the first operator and the second operator.

Abstract: An abnormality diagnosing system and method for high voltage power apparatus wherein a plurality of detectors for detecting abnormalities of the high voltage power apparatus and providing outputs indicative thereof are disposed to detect predetermined phenomena indicative of at least an insulation abnormality, power supply abnormality, and foreign matter among abnormalities existing inside of the high voltage power apparatus. A monitoring arrangement responsive to the outputs of the detectors provides at least one of an output and display of the kind of abnormality detected.

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.

Abstract: A method and apparatus for detecting insulation failure in a machine is disclosed. The machine includes an input duct for receiving a cooling gas, a gas mixture region producing a mixed gas including the cooling gas and gas produced by the thermal decomposition of insulation within the machine, and an output duct for discharging the mixed gas. A first gas sample is obtained near the input duct and a second gas sample is obtained near the output duct. An analyzer is employed to assess the difference between the first sample and the second sample. This assessment detects potential thermal decomposition of the insulation within the machine. If thermal decomposition is present, a warning signal is provided.

Abstract: Both a system and method is provided for detecting faults in the insulating interface disposed between the shaft of a generator, and the bearings and seals that rotatably support it that generally comprises a transformer for selectively inducing an alternating electric potential into the shaft while the shaft is stationary, and a voltage meter for detecting whether the transformer-induced voltage is transmitted across the insulating interfaces. The number of wire windings used in the transformer of the system is preferably chosen so that the ac voltage induced in the shaft has substantially the same characteristics as the ac voltage induced by dissymmetry currents when the shaft is rotated by the turbines which drive the electric generator. The system of the invention is capable of not only detecting the existence of an insulation failure, but also its exact location so that only the defective portion of the insulation need be repaired.

Abstract: A power apparatus in which a particle in an enclosure of the apparatus containing an electric conductor therein is moved in the enclosure by an electric field so as to cause an abnormality of insulation. The apparatus includes a first sensor for detecting an existence position of the particle on the basis of a sound of collision of the particle against the enclosure, a second sensor for detecting a partial discharge generated in the enclosure, and a device for receiving respective detection signals from the first and second sensors, for judging the existence of insulation abnormality caused by the particle inside the enclosure, and for outputting a result of the judgment.

Abstract: The present invention is a monitor that detects generator core 12 hot spots where the insulation between ferromagnetic sheets is breaking down by monitoring rotor 10 shaft voltage. The difference between the differential shaft voltage at each end of the rotor 14 produces a voltage signal that changes as the core 12 malfunctions. By comparing signal samples over time, core failure can be detected. Spring loaded rotor shaft brushes 20 and 22 connected to differential isolation amplifiers 24 and 26 obtain the voltage between ends 16 and 18 of the rotating shaft and nearby frame, and a differential amplifier 28 produces the difference between the shaft end differential voltages which is the shaft dissymmetry voltage. An analog-to-digital converter 30 produces digital values of the dissymmetry voltage which can be converted into a voltage frequency spectrum by a Fourier Transform routine executed by a computer 32 or analyzed directly.

Abstract: In the self testing refrigerator disclosed, a controller normally controls the operation of various electrical devices, such as a compressor, a blower, and an electric heater by actuating and deactuating separate relays from the power source to each of the devices. During self testing, a switch arrangement disconnects the power source supply and substitutes a high voltage dc generator having a series resistor. The same controller that controls the refrigeration operation of the devices automatically actuates the aforementioned relays separately and successively to apply the high voltage across the terminals of the electric devices and ground. The voltage across the resistor indicates the current flow through, and hence the integrity of, the insulation in each of the devices.