A battery management apparatus includes: an inverter connected to a battery cell and configured to convert a DC current output from the battery cell into an AC current according to an operation state of a plurality of switches provided therein; a measuring unit connected to a diagnosis line at which the AC current converted by the inverter is output, the measuring unit being configured to measure a voltage of the diagnosis line and output the measurement result; and a control unit having a plurality of capacitors connected to the diagnosis line and configured to control the operation state of the plurality of switches, receive the measurement result output from the measuring unit and diagnose a state of the plurality of capacitors based on the received measurement result.

A method and a system for diagnosing an open circuit (OC) fault of an insulated gate bipolar transistor (IGBT) of a T-type three-level (T.sup.23L) inverter under multiple power factors based on instantaneous current distortion are provided. Similar characteristics of current distortion may be caused by an OC fault of a T.sup.23L inverter, making it is difficult to locate the fault. The method for diagnosing an OC fault of a grid-connected T.sup.23L inverter, can diagnose the OC fault hierarchically; four switch transistors in a phase can be divided into two groups according to the similarity analysis of current distortion under different power factors; group-based fault diagnosis is realized by half cycles in which a zero domain occurs; and then, a specific switching signal is injected to realize equipment-based OC fault diagnosis. The OC fault diagnosis of a T.sup.23L inverter is realized without additional hardware circuits.

A leakage current detection circuit is used for detecting a leakage current, includes a main winding, an auxiliary winding, a detection module and a signal output module used for outputting a pulse signal with pulse signals with positive and negative alternations, wherein the main winding is connected to a leakage current detection end and coupled to the auxiliary winding, and the auxiliary winding is respectively connected to the signal output module and the detection module. During the auxiliary winding in a preset state and a leakage current occurred, the leakage current coupled to the auxiliary winding is superimposed with the pulse signal, so that the current signal detected by the detection module is greater than the current signal detected when the pulse signal with pulse signals with positive and negative alternations is not applied.

A front-end device for monitoring operation of an associated electric power device with semiconductor power switches generating a power output, e.g. a three-phase power output. The front-end device has input terminals arranged for connection to the electric phase(s) of the power output of the associated electric power device, and an electric circuit connected to the input terminals and connected to at set of output terminals. The electric circuit has a passive interconnection comprising electric semiconductor switches and diodes. The electric circuit serves to electrically block any high voltage component from the input terminals from reaching the output terminals, while allowing an on-state voltage of at least one semiconductor power switch in the associated electric power device to pass to the at least two output terminals. The front-end allows low voltage equipment to be connected to its output terminals for determining an on-state voltage of switches of the electric power device. Especially, embodiments with self-powered reference voltage circuits provided by zener diodes allow compact low cost versions for use in e.g. portable test equipment or as part of permanently installed health condition monitoring of power devices. The front-end device can be used as a simple and low cost solution for non-invasive health condition monitoring of power devices, e.g. power converters in such as power electric generation system or electric vehicles. Such monitoring allows predictive maintenance to be performed to avoid any faults in the power device that may cause permanent damages.

A method of monitoring a split wind-turbine-converter system with at least one generator-side converter and at least one grid-side converter arranged at distant locations, and a DC-link in the form of an elongated conductor arrangement with at least one positive and at least one negative conductor. The impedance of the DC-link conductor arrangement is determined by means of DC-voltage sensors. The voltages between the positive and the negative conductors are determined at the generator-side converter and at the grid-side converter, and the difference between the voltages is determined. The impedance of the DC-link conductor arrangement is determined by putting the determined voltage difference in relation to the DC current flowing through the DC-link conductor arrangement. If the impedance exceeds a given impedance threshold a fault state is recognized.

A method of monitoring a split wind-turbine-converter system with at least one generator-side converter and at least one grid-side converter arranged at distant locations, and a DC-link in the form of an elongated conductor arrangement with at least one positive and at least one negative conductor. The impedance of the DC-link conductor arrangement is determined by means of DC-voltage sensors. The voltages between the positive and the negative conductors are determined at the generator-side converter and at the grid-side converter, and the difference between the voltages is determined. The impedance of the DC-link conductor arrangement is determined by putting the determined voltage difference in relation to the DC current flowing through the DC-link conductor arrangement. If the impedance exceeds a given impedance threshold a fault state is recognized.

A system to detect a ground fault at the output of an inverter section prior to powering up a motor drive system is disclosed. A low voltage power supply is connected to the DC bus prior to connecting the input power source to the rectifier section. If a ground fault exists, the voltage potential on the DC bus causes conduction through one of the freewheeling diodes connected in parallel to the power switching device on the output of the inverter section. A fault detection circuit generates a signal corresponding to the presence of the low Voltage potential when the low voltage is applied to the DC bus. If a ground fault is present at the output of one of the inverter sections, the motor drive system prevents the AC voltage from being applied to the rectifier section.

A system to detect a ground fault at the output of an inverter section prior to powering up a motor drive system is disclosed. A low voltage power supply is connected to the DC bus prior to connecting the input power source to the rectifier section. If a ground fault exists, the voltage potential on the DC bus causes conduction through one of the freewheeling diodes connected in parallel to the power switching device on the output of the inverter section. A fault detection circuit generates a signal corresponding to the presence of the low Voltage potential when the low voltage is applied to the DC bus. If a ground fault is present at the output of one of the inverter sections, the motor drive system prevents the AC voltage from being applied to the rectifier section.

An embodiment relates to a switchgear for a single-phase motor and a three-phase motor, the switchgear including a processing unit and a first, second and third current path, the first and third current path each including a current transformer. The processing unit is adapted to detect the current I.sub.1 of the first current path and the current I.sub.3 of the third current path. To provide a cost-effective switchgear for a one-phase motor and a three-phase motor which is adapted to identify the failure of every single phase in the three-phase operation and a phase failure in the one-phase operation, the processing unit is designed such as to detect the currents I.sub.1, I.sub.3 of the first and third current path and to determine, based on the phase shift between the detected currents I.sub.1, I.sub.3 of the first and third current path in which operating mode the switchgear is operated.

A driver circuit arrangement for driving a transistor bridge, which includes at least a first half-bridge composed of a low-side transistor and a high-side transistor, is described herein. In accordance with one example of the description, the circuit includes a current source and a detection circuit. The current source is operably coupled to the high-side transistor of the first half-bridge and configured to supply a test current to the first half bridge. The detection circuit is configured to compare a voltage sense signal, which represents the voltage across the high-side transistor of the first half-bridge, with at least one first threshold to detect, dependent on the result of this comparison, whether a short-circuit is present in the first half-bridge.