Disclosed are an apparatus and a method for predicting a fault state of an inverter. The apparatus for predicting a fault state of an inverter includes: an inverter converting DC power into AC power; a switching element provided in the inverter; and a controller extracting a fault sign factor based on an output signal output from the inverter and predicting a fault of the switching element based on the fault sign factor.

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 circuit for inspecting a semiconductor device includes: the semiconductor device that is an object to be inspected and includes a diode; a protection element that is connected in series with the semiconductor device and includes a protection diode having higher breakdown resistance than the diode; a switch that includes a switching element connected in series with the semiconductor device and the protection element; and a coil that provides a loop path together with the semiconductor device and the protection element when the switching element is turned off. Even when the semiconductor device including the diode is broken, an inspection device is restricted from being damaged.

A circuit for inspecting a semiconductor device includes: the semiconductor device that is an object to be inspected and includes a diode; a protection element that is connected in series with the semiconductor device and includes a protection diode having higher breakdown resistance than the diode; a switch that includes a switching element connected in series with the semiconductor device and the protection element; and a coil that provides a loop path together with the semiconductor device and the protection element when the switching element is turned off. Even when the semiconductor device including the diode is broken, an inspection device is restricted from being damaged.

A switch short-circuited diagnosis method includes steps of: determining an initial voltage interval of multiple voltage intervals according to voltage relationships between voltages of a first phase wire, a second phase wire, and a third phase wire; performing a switch short-circuited diagnosis of a first bidirectional switch module in the three consecutive voltage intervals from the initial voltage interval, and including steps of: turning on a first switch branch, a second switch branch, or a third switch branch of the first bidirectional switch module according to the voltage relationships between the voltages of the first, second and third phase wires, determining whether an overcurrent occurs to diagnose whether the first switch branch, the second switch branch, or the third switch branch of the first bidirectional switch module is in a short-circuited state, and performing the switch short-circuited diagnosis for the next voltage interval.

A testing apparatus, including: a variable resistor coupled to a control electrode of a switching device; a storage circuit storing information indicating a relation between a resistance value of the variable resistor and a voltage change rate at which a voltage between power-source-side and ground-side electrodes of the switching device changes when the switching device is turned off; and a control circuit controlling the variable resistor. The control circuit sets the variable resistor to have a first resistance value and obtains a first value of the voltage change rate, sets the variable resistor to have a second resistance value based on the first value of the voltage change rate and the information, obtains a second value of the voltage change rate when the variable resistor is of the second resistance value, and determines whether the second value of the voltage change rate meets a specification of the switching device.

An example apparatus includes: a first switch; second and third switches coupled in series; a driver configured to: receive a first control signal; provide a second control signal having an edge having a first slope to control terminals of the first and second switches based on the first control signal; and provide a third control signal having a second edge having a second slope to a control terminal of the third switch based on the first control signal, the second slope being higher than the first slope.