US Patent 10193422 Power tool

A power tool, such as a hammer driver-drill (1), includes a brushless motor (8) having a stator (9) and a rotor (10). The stator (9) has slots (78) between teeth (63) that protrude inwardly. Coils (64) are respectively wound around each tooth (63) and the coils (64) of all phases are delta-connected in series. The rotor (10) includes permanent magnets (68) and is rotatably disposed in the interior of the stator (9). A sensor circuit board (65) is fixed to the stator (9) and includes magnetic sensors (66) that detect the rotational position of the rotor (10). The magnetic sensors (66) are provided at locations that correspond at least substantially to the centers of the slots (78) in the rotational direction of the rotor (10).