An electrical machine comprises a stator (11) having a plurality of windings (25) and a rotor (19) having a plurality of permanent magnets (26) arranged to rotate around the windings (25), the magnets (25) being mounted to an outer portion (23) of a rotor body (20), the rotor body (20) further having an inner hub portion (21) and a plurality of circumferentially-spaced arms (22) which extend radially from the hub portion (21) to the outer portion (23) of the body (20), at least one of the arms (22) comprising a vane (24) which causes an axial airflow as the rotor rotates. The axial airflow flows over the windings (25) and helps to prevent overheating without the need for any additional cooling. Since the cooling is conveniently provided by part of the rotor, the machine the machine is simple and compact.

An example electrical machine is described that includes active segments for variable voltage generation. The electrical machine includes a drive shaft, a fixed rotor segment, an active rotor segment, and an actuator mechanism. The fixed rotor segment is coupled to the drive shaft, where the fixed rotor segment has affixed thereon first permanent magnets of alternating polarity. The active rotor segment axially is adjacent to the fixed rotor segment along the drive shaft. The active rotor segment also has affixed thereon second permanent magnets of alternating polarity. The actuator mechanism is configured to articulate the active rotor segment relative to the fixed rotor segment and thereby alter a phase of the second permanent magnets relative to the first permanent magnets in order to change a first voltage generated by the electrical machine to a second voltage generated by the electrical machine.

An example electrical machine is described that includes active segments for variable voltage generation. The electrical machine includes a drive shaft, a fixed rotor segment, an active rotor segment, and an actuator mechanism. The fixed rotor segment is coupled to the drive shaft, where the fixed rotor segment has affixed thereon first permanent magnets of alternating polarity. The active rotor segment axially is adjacent to the fixed rotor segment along the drive shaft. The active rotor segment also has affixed thereon second permanent magnets of alternating polarity. The actuator mechanism is configured to articulate the active rotor segment relative to the fixed rotor segment and thereby alter a phase of the second permanent magnets relative to the first permanent magnets in order to change a first voltage generated by the electrical machine to a second voltage generated by the electrical machine.

An outer rotor of a permanent magnet assisted synchronous reluctance motor includes an annular rotor core and a plurality of permanent magnets; the annular rotor core includes a central hole; the annular rotor core further includes a plurality of slots, and the plurality of permanent magnets are disposed in the plurality of slots and form a plurality of magnetic poles along the circumferential direction of the rotor core. Each magnetic pole includes three shapes of permanent magnet: a first arc-shaped permanent magnet concentric with the rotor core, a second arc-shaped permanent magnet not concentric with the rotor core, and a rectangular permanent magnet. In each magnetic pole, the three shapes of permanent magnet are symmetrically arranged along the center line of the magnetic pole, and the first arc-shaped permanent magnet, the second arc-shaped permanent magnet and the rectangular permanent magnet are sequentially spaced radially from inside to outside.

An outer rotor of a permanent magnet assisted synchronous reluctance motor includes an annular rotor core and a plurality of permanent magnets; the annular rotor core includes a central hole; the annular rotor core further includes a plurality of slots, and the plurality of permanent magnets are disposed in the plurality of slots and form a plurality of magnetic poles along the circumferential direction of the rotor core. Each magnetic pole includes three shapes of permanent magnet: a first arc-shaped permanent magnet concentric with the rotor core, a second arc-shaped permanent magnet not concentric with the rotor core, and a rectangular permanent magnet. In each magnetic pole, the three shapes of permanent magnet are symmetrically arranged along the center line of the magnetic pole, and the first arc-shaped permanent magnet, the second arc-shaped permanent magnet and the rectangular permanent magnet are sequentially spaced radially from inside to outside.

A power tool includes an electric motor and a power supply device. The electric motor is configured to power the power tool. The electric motor includes a stator and a rotor that rotates relative to the stator and is at least partially disposed on the outer side of the stator. The power supply device is configured to supply electric energy to the electric motor. The diameter of the rotor is greater than or equal to 50 mm and less than or equal to 105 mm, and the ratio of the rated torque of the electric motor to the mass of the electric motor is higher than or equal to 4 N.Math.m/kg.

Disclosed are improved constructions for electric motors. This disclosure relates to an electric motor that employs both permanent magnets and electromagnets and that operates about a static shaft. Also disclosed in the use of a segmented rotor. A further embodiment is disclosed showing a rotor and stator that are magnetically levitated within a chamber formed by upper and lower housings.

Disclosed are improved constructions for electric motors. This disclosure relates to an electric motor that employs both permanent magnets and electromagnets and that operates about a static shaft. Also disclosed in the use of a segmented rotor. A further embodiment is disclosed showing a rotor and stator that are magnetically levitated within a chamber formed by upper and lower housings.

A brushless electric motor includes: a stator core, which includes Z tooth groups spaced apart from each other in a first circumferential direction; a rotor, which includes a magnetic ring having P poles, P being an even number; and X phase conductors, which are wound on the tooth groups to form coils, where X2, and Z=PX, wherein in the same phase conductor, the coils on two adjacent tooth groups have opposite winding directions in a second circumferential direction of the tooth groups, and are spaced apart by X1 tooth groups.

A brushless electric motor includes: a stator core, which includes Z tooth groups spaced apart from each other in a first circumferential direction; a rotor, which includes a magnetic ring having P poles, P being an even number; and X phase conductors, which are wound on the tooth groups to form coils, where X2, and Z=PX, wherein in the same phase conductor, the coils on two adjacent tooth groups have opposite winding directions in a second circumferential direction of the tooth groups, and are spaced apart by X1 tooth groups.