Abstract: A method of operating a power generation system, such as a fuel cell power generation system, includes providing a first electrical power up to a threshold amount of power to a load from at least one power module via a plurality of DC/DC converters and a DC power bus, determining whether electrical power from a utility is available, and providing a second electrical power from the at least one power module to a rectifier path via a plurality of DC/AC inverters in response to determining that the electrical power from the utility is available. The second electrical power includes electrical power generated by the at least one power module in excess of the threshold amount of electrical power.

Abstract: An uninterruptible power supply (UPS) system is provided. The UPS system includes a plurality of UPSs, a ring bus coupled to the UPSs, a plurality of chokes, and at least one static switch coupled between an associated UPS of the UPSs and the ring bus. Each choke electrically couples an associated UPS to the ring bus. The static switch is switchable to selectively bypass at least one choke.

Abstract: A power supply apparatus includes, a power generating circuit that converts energy to power and output a voltage of the power, a first switch installed on either or both of a pair of power lines, a first switch control circuit that controls the first switch based on the level of the voltage, a second switch installed on a branched line coupled to the pair of power lines, a second switch control circuit that controls the second switch based on the level of the voltage, and controls the second switch so that the second switch is repeatedly turned on and off when a power storage circuit is charged with power generated by the power generating circuit, and the power storage circuit installed on the branched line and coupled to the power generating circuit when the first switch and the second switch are set to ON states.

Abstract: Various embodiments provide power supply devices. According to an embodiment of the present disclosure, a power supply device includes: an energy storage unit configured to receive electrical energy from a first power source and store the electrical energy; a first switch unit configured to break electrical connection between the first power source and the energy storage unit when the first power source satisfies a predetermined condition; a first load connection unit electrically connected to the energy storage unit; a second load connection unit electrically connected to the energy storage unit; and a second switch unit configured to break electrical connection between the energy storage unit and the second load connection unit when the first power source satisfies the predetermined condition.

Abstract: A hybrid modular multilevel converter having fault blocking capability, and a control method thereof are disclosed. The hybrid modular multilevel converter has an ABC three-phase structure, each phase includes an identical upper arm and lower arm, and the upper arm and the lower arm are each composed of N submodules, including M unipolar full bridge submodules and N-M half bridge submodules, which are connected in series; two identical arm inductors are connected in series between a lower end of the upper arm and an upper end of the lower arm in a same phase; and upper arms and lower arms of three phases are connected in a staggered manner through six thyristor branches, the upper ends of the upper arms of the three phases are short-circuited and are connected to a DC side via a first isolating switch.

Abstract: A power source switching circuit is disclosed. The power source switching circuit includes a voltage regulator, a first transistor and a second transistor. The first transistor is coupled with a first voltage source and the second transistor is coupled with a second voltage source. The voltage regulator includes a resistor, one or more diodes coupled together in series and a capacitor. Terminals of the capacitor are coupled between a gate and a source of the first transistor through a first switch and a second switch respectively. The capacitor is configured to hold charge to switch the first transistor on. A value of the capacitor is smaller than a gate to source capacitance of the first transistor.

Abstract: A manually controlled coupling mechanism for onsite energy generation and storage systems includes a first contact portion having a first electrical contact for coupling to an utility grid and a second electrical contact for coupling to an on-grid AC terminal of an inverter, a second contact portion having a third electrical contact for coupling to an off-grid output terminal of the inverter, and a manually activated multi-position switch, wherein in a first position, only the first contact portion is activated to allow power transfer between the utility grid, the on-grid AC terminal of the inverter and a main electrical panel, and in the second position, only the second contact portion is activated to allow power transfer from the off-grid output terminal of the inverter to the main electrical panel.

Abstract: One embodiment provides an electrical circuit coupled to an alternator. The electrical circuit includes a rotor and stator coils. The electrical circuit is configured to receive, at a point when an engine is operating, an electrical current that is induced in the stator coils by rotation of the rotor and charge a battery pack with the electrical current and inhibit generation of a spark by the engine while the alternator is powered by the battery pack until a speed of the alternator is greater than a threshold. The electrical circuit is further configured to power the alternator, at a point when the engine is not operating, with electrical current supplied by the battery pack coupled to a battery connector to start the engine.

Abstract: A DER (distributed energy resource) device includes a metrology module and a communications module. The metrology module monitors the output of the DER device and the communications module provides bidirectional communications across a communications network to control the DER device. The control of the DER devices may include commands to connect the DER device to the grid, to disconnect the DER device to the grid, to connect the DER device to the premises, or to adjust a power characteristic of the output of the DER device.

Abstract: Devices and techniques for controlling voltage regulation are disclosed. A voltage regulation system may include one or more loads disposed on an integrated circuit, a DC-to-DC voltage regulation device at least partially disposed on the integrated circuit, and a second device disposed external to the integrated circuit and comprising circuitry configured to communicate with the controller of the voltage regulation device. The voltage regulation device may include one or more voltage regulation modules and a controller configured to control the one or more voltage regulation modules. The one or more voltage regulation modules may be configured to supply one or more voltage levels, respectively, to the one or more loads. The controller may be configured to disable at least one of the one or more voltage regulation modules based on a determination that the second device is not suitable for use with the voltage regulation device.

Abstract: A power conversion device includes a conversion circuit constituted of a plurality of arm circuits and a bypass circuit. The bypass circuit includes a full-wave rectification circuit, a positive-side connection arm, and a negative-side connection arm. The full-wave rectification circuit is connected between a plurality of AC connections, a positive-side intermediate node, and a negative-side intermediate node, and configured to convert AC voltages generated at the plurality of AC connections into a DC voltage across the positive-side intermediate node and the negative-side intermediate node and output the DC voltage. The positive-side connection arm blocks a current in a direction from a positive-side DC terminal toward the positive-side intermediate node. The negative-side connection arm is connected between the negative-side intermediate node and a negative-side DC terminal and blocks a current in a direction from the negative-side intermediate node toward a negative-side DC terminal.

Abstract: Electrical systems for providing uninterruptible power to a critical load. One electrical system includes a ring bus, multiple power blocks including one or more generators electrically coupled to the ring bus, and uninterruptible power supplies (UPSs) electrically coupled to the ring bus. In some aspects, the electrical system includes a UPS switchgear electrically coupled between the ring bus and the UPSs. In other aspects, the UPSs are electrically coupled together in parallel. Another electrical system includes a utility switchgear, UPS blocks electrically coupled together in parallel and electrically coupled to the utility switchgear via transformers, low voltage (LV) power blocks electrically coupled to the UPS blocks, and medium voltage (MV) switchgear electrically coupled to the UPS blocks via transformers. Each of the LV power blocks include one or more generators.

Abstract: A system (302) includes a battery powered wireless alert device (3041, . . . , 3041, . . . , 304N) and a battery powered wireless alert device monitor (3061, . . . , 3061, . . . , 306N). The battery powered wireless alert device includes electronic circuitry (2021), a transmitter (2041) configured to transmit a signal at a predetermined first rate to an alarm device (110), a logic circuit (4021) configured to generate an output signal at a predetermined second rate, wherein the first rate is lower than the second rate, and a power source (2061) configured to supply power to at least the electronic circuitry and the logic circuit.

Abstract: An electric power supply comprises first and second input circuits for receiving first and second input DC voltages and a control circuit coupled to the first and second input circuits. The control circuit is configured to sense the first input DC voltage and the second input DC voltage and to enable the first input circuit and disable the second input circuit in response to the first input circuit having the highest input DC voltage to substantially prevent current from back feeding to the first input circuit from the second input circuit. The control circuit is also configured to enable the second input circuit and disable the first input circuit in response to the second input circuit having the highest input DC voltage to substantially prevent current from back feeding to the second input circuit from the first input circuit.

Abstract: An energy harvesting apparatus, system, and method are provided to perform energy harvesting and estimation of ambient energy intensity. The energy harvesting apparatus includes an energy converter, an energy storage, an output voltage/current detector, and a switch. The energy converter receives ambient energy, converts the ambient energy into DC power having a DC voltage and a DC current, and outputs the DC power. The energy storage receives and stores the DC power. The output voltage/current detector has a constant load value and detects at least one of the DC voltage and the DC current, outputted from the energy converter, to be used for estimating intensity of the ambient energy. The switch selectively connects the energy converter to the energy storage or the output voltage/current detector.

Abstract: A vehicle supplies stable and efficient power to a load of a vehicle during a failure or performance degradation of the vehicle by forming an isolated electrical network. The vehicle includes a power supply unit, an electrical network including at least one load configured to receive power from the power supply unit, and a sensor unit that acquires at least one of current flowing in a plurality of the electrical networks and a voltage supplied to the at least one load. A power distribution module determines an insolation required portion based on the current flowing in the electrical network and the voltage supplied to the at least one load, and connects or disconnects at least one point of the electrical network based on the isolation required portion to form an isolated electrical network.

Abstract: According to an aspect, a power supply system includes a power stage, a power supply controller configured to control operations of the power stage, a metering circuit configured to sense measured conditions of the power stage, and a system performance controller configured to be coupled to the power supply controller and the metering circuit. The system performance controller is configured to set or adjust a control parameter for the power stage based on standby power of the power stage. The system performance controller includes a standby power computation circuit configured to compute the standby power of the power stage based on the measured conditions, and a control manipulation module configured to modify the control parameter until the standby power achieves a threshold condition.

Abstract: Power monitoring circuitry is provided to monitor an input system power profile of processing tasks executing on a processing platform. An input is provided to receive from the processing platform, a processing system signal indicating a power being consumed by the processing platform. A counter is provided to store a count value corresponding to an accumulated number or amount of times that a warning threshold condition associated with a warning threshold value is satisfied by the received processing system signal in a count-accumulation time interval. The count value is supplied to a power control circuit of the processing platform via a bus in response to a read request from the power control circuit, the power control circuit being responsive to the count value to control a performance level of the processing platform.

Abstract: A power converter with AFC (Automatic AC Feed Control) implements zero voltage switching when switching from a first input power supply to a second input power supply. The power converter with AFC includes a relay switchover circuit and control circuitry for selectively providing power to a connected power converter. The control circuitry uses sensed amplitude and phase values for the two input power supplies for determining when the first input power supply is lost and selectively connecting the second input power supply according to precise timing control to minimize component stress.

Abstract: The present disclosure relates to an energy storage system for managing power of a system and a DC power distribution network linked with the system. In one embodiment, the system comprises a first converter connected between the system and the DC power distribution network so as to control voltage of the DC power distribution network; a second converter connected to the DC power distribution network; a battery which is connected to the second converter and in which a charging/discharging operation is controlled by the second converter; a third converter connected to the DC power distribution network; an emergency generator which is connected to the third converter and in which a power is controlled by the third converter; a fourth converter connected to the DC power distribution network; and a first load which is connected to the fourth converter and in which a voltage is controlled by the fourth converter.

Abstract: An apparatus and methods to reduce current transient during power mode transfer in uninterruptible power supply (UPS). The disclosure provides a zero-cross detection based phase width modulated (PWM) element (E3). The element (E3) is configured to delay activation of a PWM modulator, by delaying a PWM start command for a first delay time (Tdz), wherein the first delay time is the time between receiving a static switch command to the time when a positive sequence component of a phase load current crosses zero. The element (E3) is further configured to delay the activation of the PWM modulator for a second delay time (Tdi) after the end of the first delay time (Tdz), by delaying the PWM start command for the second delay time, wherein the second delay time is based on a power factor of load connected to the UPS.

Abstract: In an uninterruptible power supply apparatus, a converter (1) is controlled such that terminal-to-terminal voltage (VDC) of a capacitor (Cd) becomes a first reference voltage (VDCr1) in an inverter power feed mode and a bypass power feed mode. In a switching period in which the inverter power feed mode and the bypass power feed mode are switched, the converter is controlled such that the terminal-to-terminal voltage of the capacitor becomes a second reference voltage (VDCr2) higher than the first reference voltage to prevent circulating current (IC) from flowing through a path including the capacitor.

Abstract: The present disclosure relates to a system for controlling power walk-in for an uninterruptible power supply (UPS) being switched to receive AC power from an AC generator. The system may have a control system and a power walk-in (PWI) subsystem. The PWI subsystem may be controlled in part by the control system. The PWI subsystem may be configured to control at least one of an input current or an input power of an AC signal being provided by an AC generator during a power walk-in operation to attempt to maintain a minimum frequency of the AC signal from the AC generator during the power walk-in operation.

Abstract: Managing power feeds includes monitoring a waveform of a high-voltage power feed supplied to an electrical load to detect potential interruption of the high-voltage power feed and switching to another power feed to supply power to the electrical load in response to identifying the waveform pattern. Monitoring a waveform includes processing the waveform to determine if one or more waveform patterns are present in the waveform. A waveform pattern indicates, by its presence in a waveform of a power feed, a power event associated with the power feed, and some waveform patterns indicate potential interruption of the power feed. Switching to another power feed in response to determining potential interruption of the power feed based on waveform monitoring enables an uninterrupted power supply.

Abstract: Technologies for transferring a load by a static transfer switch (STS) to a catcher uninterruptible power supply (UPS) are disclosed. In an illustrative embodiment, each STS in a catcher UPS system monitors an available power of the catcher UPS. The STS determines, in response to a power failure event of an associated UPS, whether a real-time power supplied to a load connected to the STS exceeds the available power of the catcher UPS and whether the STS has priority over each other STS in the system. The STS transfers the load from the associated UPS to the catcher UPS in response to determining that the real-time power supplied to the load does not exceed the available power of the catcher UPS and that the STS has priority over each other STS in the system.

Abstract: According to an embodiment, an automatic transfer switch bypass breaker system can include a first plurality of breakers configured to electrically couple a first input power source or a second input power source to common load bus via an automatic transfer switch in a first state and to electrically isolate the automatic transfer switch from the first and second input power sources and the common load bus in a second state, the first plurality of breakers including at least three breakers, and a second plurality of breakers configured to bypass the automatic transfer switch to electrically couple the first input power source or the second input power source to the common load bus in the second state, the second plurality of breakers includes at least two breakers.

Abstract: A system includes a welding power supply unit and control circuitry. The welding power supply unit includes an auxiliary power supply configured to supply power to an auxiliary power load connected to the auxiliary power supply. The control circuitry is configured to detect a voltage received by the auxiliary power load from the auxiliary power supply, compare an output voltage generated by the auxiliary power supply with the voltage received by the auxiliary power load, and apply a correction factor to the output voltage from the auxiliary power supply based at least in part on the comparison of the output voltage generated by the auxiliary power supply and the voltage received by the auxiliary power load.

Abstract: In an uninterruptible power supply system, an uninterruptible power supply operates based on a command to an inverter held in a holder before an abnormality occurs in communication when the abnormality occurs in the communication between an operation board and the uninterruptible power supply.

Abstract: A floorplan independent and cross-current free distributed adaptive power multiplexer (APM) is disclosed. In some implementations, an APM includes a first switch path coupled between a first voltage supply rail and an output terminal, the first switch path including a first switch; a second switch path coupled between a second voltage supply rail and the output terminal, the second switch path including a second switch, wherein the first switch and the second switch are configured to select one of a first voltage supply and a second voltage supply as an output voltage supply to be output at the voltage output terminal; and a comparator coupled to the first and the second voltage supply rails, and the voltage output terminal, wherein the comparator is configured to compare the output voltage supply with one of the first and the second voltage supplies and to output a control signal.

Abstract: A power supply method includes the following steps: detecting whether a battery is installed in a system; delivering a control signal to a power conversion circuit by a controller when it is determined that the battery is not installed in the system; turning on part of a plurality of transistors and turning off the other part of the plurality of transistors by the power conversion circuit according to the control signal and a reference signal, so that an input voltage is delivered to a receiving terminal of the system from a sending terminal of the system through a current path.

Abstract: A network power failure alert system for recognizing network outages and locating power failures includes a plurality of uninterruptable power sources, a plurality of location networks, and a data center. Each uninterruptable power source is configured to connect to an alternating current power source. Each location network comprises a site router and a plurality of switches. A power supply of the site router is in operational communication with the uninterruptable power source. Each switch is in operational communication with the site router and the uninterruptable power source. The data center comprises a primary core router in operational communication with the site router of each location network, the uninterruptable power source, and a plurality of network stations.

Abstract: The present application relates to a power supply arrangement comprising a power source and a switching arrangement. The switching arrangement includes a switching block, wherein the switching block includes a source interface for connecting the power source, a load interface for connecting a load and a grid interface for connecting a power grid. The switching arrangement includes further a controller for controlling the switching block in dependency of the condition of the power source. The switching arrangement is implemented as a unit separate from the power source. The power supply arrangement comprises further a monitoring device for monitoring the condition of the power source.

Abstract: An autonomous vehicle is disclosed which can map a facility and navigate its way to a particular liquid cooling system. The vehicle can be in communication with a central server, which can control the vehicle. The vehicle can align itself against the liquid cooling system and receive a computing device on a platform of the vehicle. The platform can be lowered and secured in an enclosure of the vehicle. Then, the vehicle can transport the computing device to a storage facility.

Abstract: A controller, comprising: a processing resource; and a memory resource storing machine-readable instructions to cause the processing resource to: activate a detection signal to enable a transistor coupled to the controller; determine a voltage associated with a plurality of hot swap controllers; and determine, in view of the voltage, a quantity of hot swap controllers included in the plurality of hot swap controllers.

Abstract: A switching apparatus has: first line, second line, neutral, and ground inputs; first line, second line, neutral, and ground outputs; inverter line, inverter neutral, and inverter ground inputs; inverter line, inverter neutral, and inverter ground outputs; electrical relays; and a control circuit. The first line and neutral inputs are connected to the inverter line and inverter neutral inputs, respectively; the inverter line output is connected to the first line output. With power only from the inverter output, or with single-phase power on the inverter line output and second line input, the inverter line and inverter neutral outputs are connected to the first line and neutral outputs, respectively, using the relays and control circuit. With split-phase power on the invert line output and second line input, the second line and neutral inputs are connected to the second line and neutral outputs, using the relays and control circuit.

Abstract: Various implementations described herein are directed to systems and methods for managing a plurality of loads connected to a plurality of power sources using a switching apparatus. Apparatuses described herein may include multi-throw switches designed for fast and efficient switching of loads. Methods described herein may include selecting one or more loads from a group of loads to connect to one or more alternative power sources, and selecting one or more loads to connect to a main (e.g. utility) electrical grid.

Abstract: According to aspects of the disclosure, a method and system are provided for transferring a load between a primary power source and a secondary power source. In accordance with the disclosure, a method of transferring a load between a first power source and a second power source includes analyzing a plurality of power sources to identify one or more power sources providing a power greater than a threshold value. The method also includes selecting a power source from the identified one or more power sources providing power greater than the threshold value. The method further includes connecting the selected power source to a transfer mechanism. The method still further includes actuating the transfer mechanism, using power provided to the transfer mechanism by the selected power source, to transfer the load from a connection with the first power source to a connection with the second power source.

Abstract: A chip includes a first pin coupled to a signal line and a controller to detect a state of the signal line using the first pin. The controller controls output of first power to the signal line through the first pin based on a first state of the signal line and prevents output of the first power to the signal line through the first pin based on a second state of the signal line. The signal line may be coupled to provide second power from a power source to a data storage device.

Abstract: A power supply method and a power supply apparatus including a power conversion circuit, a first and a second switching circuit, and a control circuit are provided. The power conversion circuit is coupled between a DC power source and a power supply terminal and performs a boosting operation according to a DC voltage of the DC power source to generate a boost voltage. The first switching circuit is coupled between an AC power source and the power supply terminal. The second switching circuit is coupled between the power conversion circuit and the power supply terminal. The control circuit enters a first mode after turning on the first and the second switching circuit, so the first switching circuit transmits a main AC voltage of the AC power source to the power supply terminal in the first mode. The boost voltage is greater than a peak value of the main AC voltage.

Abstract: An information processing apparatus includes an interface, a first load device, a battery, a controller, and a plurality of power transmission paths including first to third power transmission paths, wherein the controller is configured to start up the controller with power having a first power amount from an external device via the interface, request a second power amount greater than the first power amount to the external device, determine whether it is possible to receive power supply of the second power amount from the external device, supply power to the first load device via the second power transmission path to start up the first load device, and supply the power to the battery via the third power transmission path.

Abstract: An electrical power system connectable to a power grid includes a cluster of electrical power subsystems, each of the electrical power subsystems including a power converter electrically coupled to a generator having a generator rotor and a generator stator. Each of the electrical power subsystems defines a stator power path and a converter power path for providing power to the power grid. Each of the electrical power subsystems further includes a transformer. The system further includes a subsystem breaker configured with each of the electrical power subsystems, and a cluster power path extending from each subsystem breaker for connecting the cluster of electrical power subsystems to the power grid. The system further includes a reactive power compensation inverter electrically coupled within the electrical power system, the reactive power compensation inverter operable to increase the reactive power level in the electrical current flowing to the power grid.

Abstract: A power supply device according to an embodiment of the disclosure includes a power supply unit including a first power supply unit transmitting standby power to an electronic device and a second power supply unit transmitting main power to the electronic device and a cable including a standby power transmission line transmitting the standby power to the electronic device, a main power transmission line transmitting the main power to the electronic device, a first detect line receiving a power-on signal for operating the second power supply unit from the electronic device, and a second detect line determining whether the power-on signal is received. The second power supply unit does not operate when at least one of the first detect line and the second detect line is opened and the power-on signal is not received. Moreover, various embodiment grasped through the disclosure are possible.

Abstract: In at least one embodiment, a system may include a plurality of uninterruptible power supplies (UPSs), a ring bus, a plurality of chokes, with each choke of the plurality of chokes electrically coupling an associated UPS of the plurality of UPSs to the ring bus, and at least one switch electrically coupled between at least one UPS of the plurality of UPSs and the ring bus, with the at least one switch having an opening time of less than 10 milliseconds.

Abstract: A design for the electrical infrastructure of a data center enables two different configurations to be utilized, including a distributed, redundant configuration that provides higher reliability and a non-redundant configuration that provides higher capacity. In the distributed, redundant configuration, each server in the data center draws power from at least two different power supply systems. This enables load shifting when a power supply system becomes unavailable, which can have the effect of increasing server reliability. In the non-redundant configuration, each server in the data center draws power from only one power supply system. Load shifting is not utilized in the non-redundant configuration, which eliminates the need to maintain reserve capacity and thereby increases capacity. Advantageously, it is possible to switch between these two configurations without making any internal changes to the data center other than modifying connections between sets of server racks and power buses.

Abstract: A device, system, and method for providing electrical power to an electrically isolated region utilizing an electrically insulating drive shaft to transmit rotational energy over an electrically isolated gap to an electrical generator disposed in the electrically isolated region. Electrical power generated by the generator is used to power at least one electronic device in the electrically isolated region or to charge a battery, while maintaining electrical isolation.

Abstract: In a first power feeding mode, a controller supplies AC power output by an inverter to a load. In a second power feeding mode, the controller supplies AC power supplied from an AC power supply to the load. The controller switches an operation mode to the first power feeding mode when a voltage drop of the AC power supply is detected during the second power feeding mode. The controller, for a prescribed time period from detection of the voltage drop, causes a converter to perform reverse conversion to convert DC power output by a power storage device to AC power, and controls the reverse conversion in the converter such that an instantaneous value of an AC voltage output from the converter becomes equal to or higher than an instantaneous value of an AC voltage output from the inverter.

Abstract: An on-vehicle power supply device according to the present disclosure includes an electricity storage, a charge circuit, a discharge circuit, an input unit, an output unit and a controller. When the controller decides that an emergency operation condition is satisfied, the controllers causes the charge circuit to stop charging power to the electricity storage, then sets an output instruction voltage that is a target voltage value of an output of the discharge circuit to a first voltage value, the controller further causes the discharge circuit to discharge the power charged in the electricity storage, and, when the power output from the discharge circuit becomes higher than a power threshold, the controller lowers an output instruction voltage from a first voltage value to a second voltage value.

Abstract: There is provided an engine working machine capable of suppressing functional disorder of an exhaust catalyst and decline of engine performance. If, during input of a dummy load to an engine, fuel supply volume of a fuel supply device reaches a predetermined dummy load cutoff determination value as a result of elevation of a total load for an engine including the dummy load and a work load, then an electronic control device switches a load switching device to cut off the dummy load; and if, during input of the work load without including the dummy load to the engine, the fuel supply volume of the fuel supply device reaches a predetermined dummy load re-input determination value as a result of decline of the work load, then the electronic control device switches the load switching device to re-input the dummy load.

Abstract: In present solar panel theft protection system, a solar panel stops generating power after it is detached from its intended system or if the solar radiation level goes below certain min level. The accordance with the present disclosure solar panel & its connected system identify each other by encrypted codes. The solar panel & its connected system communicate with each other through same power cables which are coming from solar panel (i.e. positive & negative). No extra communication cabling is required.

Abstract: A power conversion device includes a first inverter and a control circuit that controls 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 on one low-side switch of a first specific phase among n low-side switch in the first inverter, turn off the remaining n?1 low-side switches, and turn off all n high-side switches, supplies the control signal to the n low-side switches and the n high-side switches in a state where a neutral point of a motor is provided, measures n-phase voltages that change depending on patterns of disconnection failures of the n-phase windings, and diagnoses a disconnection failure based on the measured n-phase voltages by referring to a table associating the patterns of the disconnection failures with n-phase voltage levels.