A battery power supply device includes an alternating-current power source, a secondary cell connected to the alternating-current power source, a first switch for selectively connecting or cutting off a cell and the alternating-current power source, the first switch being disposed between the battery and the alternating-current power source, and a ground fault sensing device for sensing a ground fault in the battery, the ground fault sensing device being connected closer to the battery than the first switch; the ground fault sensing device sensing a ground fault in the battery when the first switch is off.

A measuring instrument and a method checks the functional capability of an electric heating wire of a surface heating system before it is installed and indicates damage to the heating wire while it is being installed. The instrument includes a power supply, connecting devices electrically connected to the power supply and to which the free ends of an electric heating wire can be connected such as to form a current circuit on the power supply, a resistance measuring device designed to record the electric resistance of a heating wire connected to the power supply, a display device which displays an electric resistance of a heating wire recorded by the resistance measuring device, and a warning device designed to emit an acoustic signal when the electric resistance of a heating wire recorded by the resistance measuring device strays from a target value range defined by the measuring instrument.

An apparatus for testing an impedance range of a wireless power transmitter is provided. The apparatus comprises an adjustable impedance circuit configurable to be connected to a power source. The apparatus further comprises a transformer coupled the adjustable impedance circuit. The apparatus further comprises a sensing circuit configured to sense a parameter indicative of a parasitic impedance of the adjustable impedance circuit. The apparatus further comprises a driver circuit configured to drive the transformer with a signal based on the sensed parameter that causes the transformer to apply a first voltage to the adjustable impedance circuit. The first voltage has a substantially same amplitude as a voltage drop caused by the parasitic impedance. The second voltage is out of phase with the voltage drop. The sensed parameter is a current circulating in the adjustable impedance circuit or a voltage across at least a portion of the adjustable impedance circuit.

A ground fault circuit interrupter (GFCI) including separable contacts, a ground fault detection circuit structured to detect a ground fault based and to output a trip signal in response to detecting the ground fault, a trip circuit structured to trip open the separable contacts in response to the trip signal, a test button structured to be actuated by a user, a test unit structured to sequentially perform a GFCI self-test sequence and a ground fault test sequence in response to actuation of the test button, wherein the test unit is structured to determine whether the GFCI passed the GFCI self-test sequence and to output in an alarm signal in response to determining that the GFCI failed the GFCI self-test sequence, and an indicator structured to receive the alarm signal and to provide a visual or audible indication in response to receiving the alarm signal.

A transformer internal composite defect fuzzy diagnosis method based on gas dissolved in oil, comprising: a step of acquiring monitoring data of volume concentrations of five types of monitored feature gas; a step of determining ratio codes; a step of modifying a three-ratio method; a step of fuzzifying a boundary range; a step of calculating probabilities of the ratio codes; a step of calculating a probability of occurrence of each defect fault; and finally obtaining a fault type of a transformer. The method has the beneficial effects that: the method is simple and easy to achieve, and particularly suitable for being applied to an on-line transformer state monitoring system; based on a concept of fuzzy logic, diagnosis of composite defects of the transformer under a complicated state and evaluation of the degree of severity can be achieved, and the problem of sudden change caused by criterion boundary absolutisation can be effectively avoided; and multi-feature information such as an attention value and a ratio of the gas dissolved in the oil are merged and analysed, thereby effectively improving the diagnosis reliability.

A transformer test device (10) for testing a transformer (40) has connections (12) for releasably connecting the transformer test device (10) to the transformer (40). The transformer test device (10) has a source (13) for generating a test signal for testing the transformer (40). The transformer test device (10) has a controllable switching means (15) which is connected to the connections (12) during a transformer test for the purpose of short-circuiting at least one winding (42) of the transformer (40).

The objective of the present invention is to provide an electric power converting device with which can executes a ground fault detection in a short time with its inexpensive configuration. In one step, the electric power converting device performs level comparison of a difference between output values of low pass filters, with a threshold value −E. If a W-phase is shorted to ground at a time when the U-phase and V-phase lower arm IGBTs are ON and W-phase upper IGBT is ON, the difference between the output values of the low pass filters and becomes small. In another step, a level comparison is made between the absolute value of a difference between the U-phase current value iu and U-phase current command value iu′, and a threshold value F. If the absolute value is lower than the threshold value, the result is determined to be normal, and if the absolute value is greater than the threshold value, the result is determined to be abnormal, because the U-phase is shorted to ground. In another step, a level comparison is made between the absolute value of a difference between the V-phase current iv and the V-phase current command value iv′, and a threshold value F. If the absolute value is lower than the threshold value, the result is determined to be normal, and if the absolute value is greater than the threshold value, the result is determined to be abnormal, because the V-phase is shorted to ground.

An engine coolant temperature sensor configured to earth through the engine coolant such that an alarm will trigger when coolant is absent.

The invention concerns a method for monitoring a cable strand containing multiple electrical lines, such that the cable strand is designed to conduct electrical energy generated by a generator in a wind turbine involving the steps: measuring the temperature of at least two of the electrical lines, comparing the temperatures of said lines, and determining whether the two temperatures deviate from one another by more than a predefined threshold.

A method for identifying electrical faults in a generator assemblage, in particular of a motor vehicle, which assemblage includes a generator having a generator regulator and a rectifier having rectifier elements, the method encompassing ascertaining, in the context of at least one excitation current value of an excitation current through an excitation winding of the generator, at least one respective parameter that corresponds to a current conduction time proportion of at least one of the rectifier elements, and determining that an electrical fault exists if the at least one parameter deviates by more than a predetermined amount from an associated expected value. Also described is an apparatus for implementing the method.