A motor driving device and an air conditioner are capable of increasing the efficiency in a low speed region in which a motor performs low speed rotation. The motor driving device that is a motor driving device for driving a motor including stator windings, includes: a connection switching unit that switches connection condition of the stator windings to either of first connection condition and second connection condition different from the first connection condition; and an inverter that converts a DC voltage into AC drive voltages and supplies the AC drive voltages to the stator windings. The inverter includes MOS transistors as switching elements.

An engine generator, including a general purpose engine, an engine speed of the engine being variably controlled, a generator unit having a three-phase winding and driven by the engine to generate power, an inverter unit converting AC output from the generator unit to AC of a predetermined frequency to output to a load, a connection switching unit switching a connection configuration of the winding to one of a wye-connection and a delta-connection, a load detection unit detecting a size of the load, and a connection switching control unit controlling the connection switching unit to switch the connection configuration to the wye-connection when the size of the load is equal to or lower than a predetermined value, and to switch the connection configuration to the delta-connection when the size of the load is higher than the predetermined value.

A signal level adjustment apparatus includes a detector configured to detect both a plurality of peak levels of an input signal having a sinusoidal waveform or a substantially sinusoidal waveform and a plurality of bottom levels of the input signal; and a level adjuster configured to adjust, in a predetermined zone of the input signal, levels of the input signal based on the plurality of peak levels and the plurality of bottom levels detected by the detector.

One embodiment describes a tangible, non-transitory, computer-readable medium storing instructions executable by a processor in a control circuitry. The instructions include instructions to receive an instruction to make a switching device; determine, using the control circuitry, a voltage waveform of a power source; determine, using the control circuitry, a desired time to make the switching device based at least in part on the source voltage waveform; determine, using the control circuitry, an expected make time of the switching device; and determine, using the control circuitry, when to apply a pull-in current to make the switching device at the desired time based at least in part on the expected make time and the desired time to make.

A method and system of performing a pole switching operation in a multi-phase machine include operating the multi-phase machine in a first configuration with a first number of poles, where the first number of poles is based on a first number of phases in the first configuration and a number of stator slots allocated for each winding in the multi-phase machine. The method and system also include receiving a signal indicating the pole switching operation in the multi-phase machine. In response to receiving the signal, the method and system include operating the multi-phase machine in a second configuration with a second number of poles, where the second number of poles is based on a second number of phases in the second configuration and the number of stator slots allocated for each winding in the multi-phase machine.

A driving device drives a motor having coils. The driving device includes a connection switching unit to switch a connection state of the coils, a temperature sensor to detect a room temperature, and a controller to switch the connection state of the coils based on a detected temperature by the temperature sensor.

An air conditioner includes a signal receiving unit to receive an operation instruction signal, a compressor including a motor including coils, an inverter connected to the coils, a connection switching unit to switch a connection state of the coils between a first connection state and a second connection state, and a controller to control the inverter and the connection switching unit. When the signal receiving unit receives an operation stop signal, the connection switching unit switches the connection state of the coils from the first connection state to the second connection state.

One embodiment describes a switching device system, which includes a first single pole switching device that selectively connects and disconnects a first phase of electric power to a first winding of a three phase motor; a second single switching device that selectively connects and disconnects a second phase of electric power to a second winding of the three phase motor; in which the first and second single pole switching devices control temperature of the motor by, at a first time, connecting the first phase and the second phase electric power to the motor.

A switching device, for a wye-delta switch in a multiphase motor each phase having one motor winding having a connection pair and contact device (CD), has an electromagnetic drive for drive axle movement between three axial positions, the CD having first and second motor winding connection contacts (MWCC), phase connection contact (PCC), and movable contact bridge (MCB) coupled to the drive axle and movable thereby into the three positions. In position-1, axially between positions-2/3, the MCB is openno CC is connected to another CC by the MCB; in position-2, the MCB is in wye contact positionthe MCB connects the PCC to the first MWCC, and the second MWCC is connected to the second MWCC of all other CDs using the wye coupled to the drive axle; and in position-3, the MCB is in a delta contact positionthe MCB connects the FCC to the first and second MWCC.

A switching device, for a wye-delta switch in a multiphase motor each phase having one motor winding having a connection pair and contact device (CD), has an electromagnetic drive for drive axle movement between three axial positions, the CD having first and second motor winding connection contacts (MWCC), phase connection contact (PCC), and movable contact bridge (MCB) coupled to the drive axle and movable thereby into the three positions. In position-1, axially between positions-2/3, the MCB is openno CC is connected to another CC by the MCB; in position-2, the MCB is in wye contact positionthe MCB connects the PCC to the first MWCC, and the second MWCC is connected to the second MWCC of all other CDs using the wye coupled to the drive axle; and in position-3, the MCB is in a delta contact positionthe MCB connects the FCC to the first and second MWCC.