To provide a power tool capable of suppressing variations in motor characteristics between external power sources with different voltage while preventing an increase in the size of the power tool. The power tool includes: a motor including a stator on which a plurality of windings are wound and a rotor rotatable relative to the stator; an output unit driven by rotation of the rotor; a power source connection part connectable to an external power source serving as a driving power source of the motor; power source voltage detecting means configured to perform detecting a voltage of the external power source connected to the power source connection part; and connection form changing means configured to perform changing a connection form of the plurality of windings on the basis of the voltage of the external power source.

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.