A load testing device includes a connection unit to which a power source being tested is connected, a hydrogen generating unit that performs electrolysis based on power supplied from the power source being tested to generate hydrogen, two or more supply units to which hydrogen obtained in the hydrogen generating unit passes and to which a portable tank is removably attached, and an operational unit that has a load amount adjustment switch and a display unit. The load amount of the hydrogen generating unit is switched depending on an operational state of the load amount adjustment switch. The display unit displays at least one of an attachment status of the portable tank and a filling status of hydrogen in the two or more supply units.

A load testing device includes a connection unit to which a power source being tested is connected, a hydrogen generating unit that performs electrolysis based on power supplied from the power source being tested to generate hydrogen, two or more supply units to which hydrogen obtained in the hydrogen generating unit passes and to which a portable tank is removably attached, and an operational unit that has a load amount adjustment switch and a display unit. The load amount of the hydrogen generating unit is switched depending on an operational state of the load amount adjustment switch. The display unit displays at least one of an attachment status of the portable tank and a filling status of hydrogen in the two or more supply units.

Embodiments of the present disclosure describe frequency detection techniques for detecting power irregularities. These irregularities may include variations or abnormalities in switched-mode power supply circuit switching behavior, power spikes, and/or output oscillations. The frequency detection techniques may compare different frequency components of the power signal to detect irregularities.

The present disclosure relates to a device and a method for diagnosing a failure of an inverter initial charging circuit. The device for diagnosing a failure of an initial charging circuit according to the present invention is advantageous as follows: it is possible to detect whether a relay of the initial charging circuit is malfunctioning or not by using a photocoupler connected in parallel with an initial charging resistor of the initial charging circuit, on the basis that, if a current flows through the initial charging resistor in a relay-on state, the photocoupler is turned on; and it is possible to prevent component failure or burnout from occurring due to a high current flowing through the initial charging resistor in the case of a relay failure.

A power conversion device includes a first inverter and a control circuit that controls an on/off operations of switches in the first inverter and diagnoses disconnection failures of n-phase windings, where n is an integer of three or more. The control circuit generates a control signal to turn off all of n low-side switches and n high-side switches, supplies the control signal to the n low-side switches and the n high-side switches and measures the n-phase voltages that change depending on patterns of on failures of the switches, and executes a first failure diagnosis to diagnose the on failures of the n low-side switches and the n high-side switches based on the measured n-phase voltages by referring to a table associating the patterns of the on failures of the switches with n-phase voltage levels.

A load testing device includes: a resistance unit; a cooling fan that cools the resistance unit; a circuit breaker; a first terminal part that is connected to a test target power source; and a charge/discharge unit that has a charger and a first power storage device. The charge/discharge unit is connected with a test target power source cable being between the first terminal part and the resistance unit, between the first terminal part and the circuit breaker. The first power storage device 45a stores electric power supplied from the test target power source. The cooling fan drives based on electric power from at least the charge/discharge unit.

A load testing device includes: a resistance unit; a cooling fan that cools the resistance unit; a circuit breaker; a first terminal part that is connected to a test target power source; and a charge/discharge unit that has a charger and a first power storage device. The charge/discharge unit is connected with a test target power source cable being between the first terminal part and the resistance unit, between the first terminal part and the circuit breaker. The first power storage device 45a stores electric power supplied from the test target power source. The cooling fan drives based on electric power from at least the charge/discharge unit.

A system and method that identify a location and/or magnitude of a ground fault in a circuit having a bus that connects battery strings with loads and a ground reference between the loads are provided. Potential of the bus is shifted relative to a ground reference in a first direction. A first impedance in the bus between the battery strings and the ground reference is determined, and the bus is shifted relative to the ground reference in a second direction. A second impedance in the bus between the battery strings and the ground reference is determined. A location and/or severity of a ground fault is determined based on a relationship between the first impedance and the second impedance.

A control system for a wireless power transfer (WPT) system includes current sampling modules, voltage sampling modules, a logic conversion circuit, and a controller area network (CAN) communication module that are all connected to a microprocessor module; the current sampling module is connected to the logic conversion circuit through a signal isolation circuit, the logic conversion circuit is connected to a pulse-width modulation (PWM) module, the PWM module is connected to an inverter circuit or a DC/DC converter, and the current sampling module and the voltage sampling module are connected to a primary side or a secondary side of the WPT system; transmitter coils on the primary side are spaced apart on the road, a receiver coil on the secondary side is disposed on a chassis of an electric vehicle, and the transmitter coil includes a double rectangular coil, a ferrite core surface, and a shielding aluminum plate.

A method for calculating the steady-state fault current of a modular multilevel converter (MMC) comprises calculating the dc-side critical resistance values R.sub.A/B, R.sub.B/C and R.sub.C/D of the MMC based on the bridge arm inductance coefficient k and the ac-side reactance X.sub.ac of the MMC; Then, determining the operating modes of the MMC based on R.sub.A/B, R.sub.B/C and R.sub.C/D, and calculating the steady-state dc fault current and the conduction overlap angle respectively under various operating modes without considering the ac-side resistance based on the parameters k, U.sub.s, R.sub.dc and the dc-side critical resistance values R.sub.A/B, R.sub.B/C and R.sub.C/D; After that the steady-state AC fault current amplitude and phase angle for each operating mode without considering the AC side resistance are calculated based on the DC current and conduction overlap angle for each operating mode, respectively. Finally, the steady-state AC fault current amplitude and phase angle are calculated for various operating modes considering the AC side resistance.