A system for estimating a severity of a bearing fault in an induction motor, uses a set of filters and a set of quantitative models designed for a set of fault frequencies. The system, upon receiving the measurements of the stator current, extracts the first fault current from the stator current using the first filter, determine the first mutual inductance variation from the first fault current using the first quantitative model, and classify the first mutual inductance variation with the fault severity classifier to determine the severity of a first type of fault in the induction motor. Similarly, the system classifies a second type of fault using the second filter and the second quantitative model. The system outputs one or combination of the severity of the first type of fault in the induction motor and the severity of the second type of fault in the induction motor.

The invention relates to a novel approach for the protection of electrical circuits from ground faults and parallel and series arc faults in a fully solid-state circuit configuration. Solid-state circuits and methods of use are described that provide the key functions of low-voltage DC power supply, mains voltage and current sensing, fault detection processing and high voltage electronic switching.

The invention relates to a novel approach for the protection of electrical circuits from ground faults and parallel and series arc faults in a fully solid-state circuit configuration. Solid-state circuits and methods of use are described that provide the key functions of low-voltage DC power supply, mains voltage and current sensing, fault detection processing and high voltage electronic switching.

The invention relates to a novel approach for the protection of electrical circuits from ground faults and parallel and series arc faults in a fully solid-state circuit configuration. Solid-state circuits and methods of use are described that provide the key functions of low-voltage DC power supply, mains voltage and current sensing, fault detection processing and high voltage electronic switching.

The invention relates to a novel approach for the protection of electrical circuits from ground faults and parallel and series arc faults in a fully solid-state circuit configuration. Solid-state circuits and methods of use are described that provide the key functions of low-voltage DC power supply, mains voltage and current sensing, fault detection processing and high voltage electronic switching.

A system includes a transformer rectifier unit (TRU) having three inputs, a first AC bus configured to supply power to a first of the three inputs, a second AC bus configured to supply power to a second of the three inputs, and a third AC bus configured to supply power to a third of the three inputs. The system includes a power quality sense device electrically connected to each of the first, second and third AC busses. The system includes an electrically held contactor electrically connected between the TRU and the power quality sense device. The electrically held contactor is configured and adapted to be switched ON or OFF depending on whether the power quality sense device is energized or de-energized.

An electrical device includes a first terminal structured to electrically connect to a power source; a second terminal structured to electrically connect to a load; a voltage sensor electrically connected to a point between the first and second terminals and being structured to sense a voltage at the point between the first and second terminals; a switch electrically connected between the first terminal and the second terminal; and a control unit structured to detect a power quality event in the power flowing between the first and second terminals based on the sensed voltage and to control a state of the switch based on the detected power quality event.

The invention relates to a detection device (100) for detecting an arc (104a-i; 909) occurring between a first current-carrying element (103; 903a) and at least one conductive element (103b, 108; 903b, 907), comprising at least one measuring device (101; 901, 902), which is designed to measure a current (I) flowing through the first current-carrying element (103a; 903a), and an analysis device (102) which is designed to determine a frequency spectrum of the measured current (I) and to detect the arc (104a-i; 909) occurring between the first current-carrying element (103a; 903a) and the at least one conductive element (103b, 108; 903b, 907) on the basis of a high-frequency range of the determined frequency spectrum.

The invention relates to a detection device (100) for detecting an arc (104a-i; 909) occurring between a first current-carrying element (103; 903a) and at least one conductive element (103b, 108; 903b, 907), comprising at least one measuring device (101; 901, 902), which is designed to measure a current (I) flowing through the first current-carrying element (103a; 903a), and an analysis device (102) which is designed to determine a frequency spectrum of the measured current (I) and to detect the arc (104a-i; 909) occurring between the first current-carrying element (103a; 903a) and the at least one conductive element (103b, 108; 903b, 907) on the basis of a high-frequency range of the determined frequency spectrum.

An embodiment of the invention relates to a method for ground fault detection for low-voltage three-phase AC circuits having a neutral conductor, in which first to fourth analog current signals of the first to third phase conductors and of the neutral conductor of the three-phase AC circuit are ascertained that each contain the level or an equivalent of the level of the current. The analog current signals are time-division multiplexed, subjected to a/d conversion, and a sequence of time-division-multiplexed first to fourth digital current values present in first to fourth successive time frames form first to fourth current signals. Three of the four digital current signals are interpolated to ascertain interpolated current values. The current value of the time frame of the uninterpolated current signal and the interpolated current values for the time frame of the uninterpolated current signal are used for discovering the ground fault.