A motor driving system includes first and second motors including multiple first windings and second windings; a first inverter including a DC terminal connected to a DC voltage source and an AC terminal connected to the multiple first windings; a first switch part including a plurality of first mode change switches connected to the multiple first windings; a second inverter including a DC terminal connected to the DC voltage source and an AC terminal connected to the plurality of first mode change switches; a second switch part including a plurality of second mode change switches connected to the AC terminal of the second inverter and the multiple second windings; a third switch part including a plurality of third mode change switches connected to the multiple first windings; and a controller configured to control the short-circuited state or the open state of the multiple first mode, second and third mode change switches, based on whether the first and the second motors are driven.

A motor driving system includes first and second motors including multiple first windings and second windings; a first inverter including a DC terminal connected to a DC voltage source and an AC terminal connected to the multiple first windings; a first switch part including a plurality of first mode change switches connected to the multiple first windings; a second inverter including a DC terminal connected to the DC voltage source and an AC terminal connected to the plurality of first mode change switches; a second switch part including a plurality of second mode change switches connected to the AC terminal of the second inverter and the multiple second windings; a third switch part including a plurality of third mode change switches connected to the multiple first windings; and a controller configured to control the short-circuited state or the open state of the multiple first mode, second and third mode change switches, based on whether the first and the second motors are driven.

An air conditioning apparatus includes an indoor unit and an outdoor unit. The outdoor unit includes a compressor that compresses a refrigerant and a motor drive apparatus that drives the compressor. The motor drive apparatus includes an inverter that converts a direct-current voltage into an alternating-current voltage and a motor that operates on the alternating-current voltage from the inverter. The motor includes six stator windings that are each openable at both ends. The motor drive apparatus further includes a connection state switching unit that includes a function of switching a connection state of the six stator windings of the motor among at least four types of connection states.

An air conditioning apparatus includes an indoor unit and an outdoor unit. The outdoor unit includes a compressor that compresses a refrigerant and a motor drive apparatus that drives the compressor. The motor drive apparatus includes an inverter that converts a direct-current voltage into an alternating-current voltage and a motor that operates on the alternating-current voltage from the inverter. The motor includes six stator windings that are each openable at both ends. The motor drive apparatus further includes a connection state switching unit that includes a function of switching a connection state of the six stator windings of the motor among at least four types of connection states.

An electric motor system implements a redundant wye-wounded motor that includes first phase leads, second phase leads, first neutral leads, and second neutral leads. The first and second phase leads receive alternating current (AC) power from a power supply. A first phase-lead switch selectively connects the first phase leads to the power supply, and a second phase-lead switch selectively connects the second phase leads to the power supply. A first neutral-lead switch selectively connects the first neutral leads to the redundant wye-wounded motor, and a second neutral-lead switch selectively connects the second neutral leads to the redundant wye-wounded motor. A controller detects a circuit fault among a plurality of different types of circuit faults, and controls the operation of one or both of the primary neutral-lead switch and the second neutral-lead switch based on the circuit fault.

A wall-mountable load control device may include an illuminated rotary knob for providing a nightlight feature. The load control device may be configured to control an intensity of a lighting load. The load control device may include a yoke adapted to be mounted to an electrical wall box, an enclosure attached to the yoke, a faceplate attached to the yoke and having an opening, a mounting member attached to the yoke, and/or a potentiometer located within the enclosure and having a shaft extending through an opening in the yoke and the opening of the faceplate. The load control device may include a collar attached to the boss of the mounting member and surrounding the shaft of the potentiometer. The mounting member may be configured to conduct light from at least one light source housed within the enclosure to illuminate the faceplate.

A motor driving device is a device for driving a motor including stator windings, includes: a connection switching unit that is connected to the stator windings, includes circuits including semiconductor switches, and switches connection condition of the stator windings to either of first connection condition and second connection condition different from the first connection condition by setting the semiconductor switches to ON or OFF; and an inverter that supplies AC drive voltages to the stator windings.

A driving device includes an inverter to output a voltage to coils, a connection switching unit to switch a connection state of the coils between a Y connection and a delta connection, and a controller. The controller causes the inverter to stop outputting, when the connection state of the coils is the Y connection and a current value of the inverter reaches a first threshold A, or when the connection state of the coils is the delta connection and the current value of the inverter reaches a second threshold B. The first threshold A and the second threshold B satisfy B<√3×A.

A driving device includes an inverter to output a voltage to coils, a connection switching unit to switch a connection state of the coils between a Y connection and a delta connection, and a controller. The controller causes the inverter to stop outputting, when the connection state of the coils is the Y connection and a current value of the inverter reaches a first threshold A, or when the connection state of the coils is the delta connection and the current value of the inverter reaches a second threshold B. The first threshold A and the second threshold B satisfy B<√3×A.

A wall-mountable load control device may include an illuminated rotary knob for providing a nightlight feature. The load control device may be configured to control an intensity of a lighting load. The load control device may include a yoke adapted to be mounted to an electrical wall box, an enclosure attached to the yoke, a faceplate attached to the yoke and having an opening, a mounting member attached to the yoke, and/or a potentiometer located within the enclosure and having a shaft extending through an opening in the yoke and the opening of the faceplate. The load control device may include a collar attached to the boss of the mounting member and surrounding the shaft of the potentiometer. The mounting member may be configured to conduct light from at least one light source housed within the enclosure to illuminate the faceplate.