An electric tool is provided with a rotary striking mechanism unit converting the rotational force of a brushless motor to a striking force and applying the striking force to a tip tool. The required rated input of the motor is 1000-1300 W, the motor speed under fixed speed control is 1680010% (min.sup.1), and the variable Ku, which relates to the motor, is defined by the following expression Ku={(stator core outer diameter).sup.2(stator core lamination thickness)(total tooth width)(rotor outer diameter)}{(rated input)(motor speed under fixed speed control)}, wherein the stator core outer diameter, the stator core lamination thickness, the total tooth width and the rotor outer diameter are shown in mm, the rated input is shown in W, the motor speed is shown in min.sup.1, and the Ku value of the motor is set to 14.6Ku21.8.

An electric tool is provided with a rotary striking mechanism unit converting the rotational force of a brushless motor to a striking force and applying the striking force to a tip tool. The required rated input of the motor is 1000-1300 W, the motor speed under fixed speed control is 1680010% (min.sup.1), and the variable Ku, which relates to the motor, is defined by the following expression Ku={(stator core outer diameter).sup.2(stator core lamination thickness)(total tooth width)(rotor outer diameter)}{(rated input)(motor speed under fixed speed control)}, wherein the stator core outer diameter, the stator core lamination thickness, the total tooth width and the rotor outer diameter are shown in mm, the rated input is shown in W, the motor speed is shown in min.sup.1, and the Ku value of the motor is set to 14.6Ku21.8.

An oil lubricated compressor having a universal motor, efficient starting and re-starting characteristics, and a long operating life. The oil lubricated compressor can have a brushed or brushless universal motor which can drive a cooling fan and a pump. The universal motor can achieve a high torque to voltage ratio, as well as a high torque to current ratio, upon starting or re-starting of the compressor. Optionally, the oil lubricated compressor can use a single cooling fan disposed in the compressor at a location which is between the universal motor and a cylinder head of the pump.

An oil lubricated compressor having a universal motor, efficient starting and re-starting characteristics, and a long operating life. The oil lubricated compressor can have a brushed or brushless universal motor which can drive a cooling fan and a pump. The universal motor can achieve a high torque to voltage ratio, as well as a high torque to current ratio, upon starting or re-starting of the compressor. Optionally, the oil lubricated compressor can use a single cooling fan disposed in the compressor at a location which is between the universal motor and a cylinder head of the pump.

A brushless motor includes a stator and a rotor. The stator includes a stator core and a plurality of windings. The stator core includes a yoke, and a plurality of teeth extending from the yoke. Each of the teeth comprising two pole shoes extending in opposite ways along a circumferential direction of the yoke. Pole shoes of adjacent teeth are connected through a magnetic bridge having a larger magnetic reluctance than that of the poles shoes, which reduces the magnetic leakage and increases the motor power density. Axial thickness of each of the magnetic bridges is smaller than that of the poles shoes.

A brushless direct current (DC) motor, including a motor body and a motor controller. The motor controller includes a control box and a control circuit board. The motor body is a plastic-packaged body including a rotary shaft, a rotor assembly, a plastic-packaged stator, a front cover, and a rear cover. The rotor assembly is disposed on the rotary shaft. The plastic-packaged stator is sleeved on the outer side of the rotor assembly. The front cover is disposed on the front part of the plastic-packaged stator. The plastic-packaged stator includes a stator core, a terminal insulator, coil windings, and a plastic-packaged shell. The terminal insulator is disposed on one end of the stator core. The coil windings are coiled on the terminal insulator. The plastic-packaged shell is adapted to connect the stator core, the terminal insulator, and the coil windings together.

A direct current machine comprises a stator and a rotor, wherein one of these two has a plurality of magnets which are alternatively magnetized north and south, and the respective other part has a plurality of coils which are formed by teeth around which insulated wire is wound, wherein between these coils there are formed respective slots and the coils are combined in coil groups; and a current controlled inverter for driving the machine; wherein each coil group has a front terminal and a rear terminal and the coil groups are connected such that a defined wiring concept is formed and wherein the front terminals and end terminals are connected via an interconnection element which is specifically designed for a defined wiring concept.

A direct current machine comprises a stator and a rotor, wherein one of these two has a plurality of magnets which are alternatively magnetized north and south, and the respective other part has a plurality of coils which are formed by teeth around which insulated wire is wound, wherein between these coils there are formed respective slots and the coils are combined in coil groups; and a current controlled inverter for driving the machine; wherein each coil group has a front terminal and a rear terminal and the coil groups are connected such that a defined wiring concept is formed and wherein the front terminals and end terminals are connected via an interconnection element which is specifically designed for a defined wiring concept.

In a thyristor control device which converts a first AC voltage to a DC voltage and converts the DC voltage to a second AC voltage to be supplied to a synchronous motor, a DC voltage detector is configured to detect the DC voltage, and is provided with an AC voltage detector configured to detect the second AC voltage and an arithmetic circuit configured to determine the DC voltage on the basis of the second AC voltage detected by the AC voltage detector. As a result, there is no need to separately provide a DV voltage detector, which makes it possible to make the device compact in size and cheap in price.

A brushless motor is provided that includes a rotor, a stator, a bearing member, an attraction magnet, and a yoke. The rotor includes a shaft, a rotor yoke that holds the shaft and covers a peripheral surface of the shaft, and a magnet disposed around an outer periphery of the rotor yoke. The stator is disposed around an outer periphery of the rotor. An inner wall of a housing serving as a bearing member rotatably holds the shaft with a bearing. The attraction magnet is disposed at an end portion of the inner wall at which the rotor yoke holds the shaft, and produces an attraction force to attract the rotor yoke. The yoke supplements and enhances the attraction force produced by the attraction magnet.