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<3A.

A motor has stator windings arranged on a circumference of a stator, a rotor with rotor magnetic poles provided by N- and S-poles, and rotor windings arranged in a circumferential direction of the rotor magnetic poles. Multiple-phase currents are supplied to the stator windings. A current is supplied to rotor windings. The multiple-phase currents include torque current components, which are arranged to be opposite in directions to torque current components of the current. By this mutually opposite-directional current arrangement, a magnetomotive force based on a sum of both torque current components becomes a local minimum. It is possible to reduce influence of the torque current components on the field magnetic fluxes of the motor. In the motor, circumferential magnetic flux components can be collected to an airgap and a portion therearound, so that a larger amount of torque can be obtained, and constant output control can be performed more easily.

A motor is provided with stator windings arranged on a circumference of stator. Multiple-phase currents are supplied to the stator windings. A current is supplied to rotor windings. The multiple-phase currents include torque current components, which are arranged to be opposite in directions to torque current components of the current. By this mutually opposite-directional current arrangement, a sum of both torque current components results in a magnetomotive force of zero. It is also possible to reduce influence of the torque current components on the field magnetic fluxes of the motor. In the motor, circumferential magnetic flux components can be concentrated on an airgap and a portion near therearound, so that a larger amount of torque can be obtained, and constant output control can be performed more easily.

A motor control device includes coil temperature detection means, cooling oil temperature detection means, and a control unit. The control unit implements a coil protection torque restriction and a cooling oil protection torque restriction. The control unit makes it easier for the coil protection torque restriction to be preferentially implemented in a low rotation operating region in which a motor operates at a low rotation speed equal to or lower than a predetermined value, and makes it easier for the cooling oil protection torque restriction to be preferentially implemented in a high rotation operating region in which the motor operates at a higher rotation speed than in the low rotation operating region.

A hybrid electrical machine containing surface mounted magnets which includes a magnetically permeable cylindrically shaped stator assembly having at least one stator winding formed about a plurality of stator teeth, a rotor assembly concentrically disposed within the stator assembly, including a magnetically permeable rotor backiron, a rotational drive mechanism coupled to the rotor backiron, and a plurality of protruding rotor poles, each including a magnetically permeable pole support assembly, a winding provided around the pole support assembly, and a radially magnetized permanent magnet assembly disposed about the pole support assembly.

A pump assembly (1) includes a pump unit (2) capable of providing a desired head (H.sub.0) at zero flow rate, a brushless speed-controlled permanent-magnet AC drive motor (205) for driving the pump unit (2), and a control unit for controlling the drive motor (205). The control unit includes a frequency converter configured to receive an input voltage (U.sub.in). The drive motor (205) is operable in a field-weakening mode and non-field-weakening mode. The drive motor (205) is undersized for driving the pump unit (2) at a design input voltage (U.sub.0) to provide a lower head (H) than the desired head (H.sub.0) at zero flow rate in the non-field-weakening mode and for driving the pump unit (2) to provide the desired head (H.sub.0) at zero flow rate in the field-weakening mode.

A motor control device includes: a voltage boosting circuit that boosts a power source voltage supplied from an outside; a condenser that smooths a voltage output by the voltage boosting circuit; an inverter circuit that generates a drive voltage of a motor by switching a voltage output by the voltage boosting circuit and smoothed by the condenser; and a control part that causes the voltage boosting circuit to bypass and causes the power source voltage to be supplied to the inverter circuit, and a distance between the voltage boosting circuit and the inverter circuit is a distance with which a parasitic inductance is equal to or less than a predetermined value.

A motor includes: a housing that accommodates a stator that has a field coil and a rotor; an inverter that is provided in the housing; a voltage boosting circuit that has a reactor provided in the housing; and a coolant flow path that is provided at a position at which the coolant flow path overlaps with the inverter and the voltage boosting circuit in the housing in a diameter direction, and the inverter has a control board that controls a drive current or a drive voltage and a drive element that is provided on the side of the housing with respect to the control board and supplies power to the field coil in accordance with control from the control board.

A hybrid electrical machine containing surface mounted magnets which includes a magnetically permeable cylindrically shaped stator assembly having at least one stator winding formed about a plurality of stator teeth, a rotor assembly concentrically disposed within the stator assembly, including a magnetically permeable rotor backiron, a rotational drive mechanism coupled to the rotor backiron, and a plurality of protruding rotor poles, each including a magnetically permeable pole support assembly, a winding provided around the pole support assembly, and a radially magnetized permanent magnet assembly disposed about the pole support assembly.

A power tool includes a brushless motor, a supplying circuit, and a controller. The brushless motor is configured to drive and rotate when a voltage applied to the brushless motor is larger than or equal to an induced voltage. The supplying circuit is configured to apply a driving voltage to the brushless motor. The controller is configured to control the supplying circuit. The supplying circuit includes a rectifying circuit, a capacitor, and a switching circuit. The rectifying circuit is configured to rectify an alternating voltage and output a rectified voltage. The capacitor is configured to smooth the voltage inputted via the rectifying circuit. The switching circuit is configured to perform a switching operation based on a PWM signal to adjust a period during which the driving voltage is applied. The controller is configured to set a duty ratio within a prescribed range, and output the PWM signal of the set duty ratio to the switching circuit to control the switching operation. The controller is configured to perform a constant-number-of-rotation control for controlling the brushless motor to rotate at a target rotation number by changing the duty ratio. The capacitor has a capacitance allowing a smoothed voltage to be always larger than or equal to the induced voltage during the constant-number-of-rotation control.