Abstract: A commutator for rotation with or by the shaft of a electrical machine has first and second electrically conductive commutator segments provided on a base for electrical engagement with brushes connected to windings. Isolated from and interspersed between the commutator segments are first and second freewheeling segments. A first diode is connected between the first commutator segment and the first freewheeling segment. A second diode is connected between the second commutator segment and the second freewheeling segment. The diodes allow current to flow in only one direction between the commutator and freewheeling segments to help suppress commutation sparking.

Abstract: A rotating electrical machine has a housing with a shaft mounted rotatably in it. A rotor is fixed to the shaft and has a plurality of magnetic poles. A stator is positioned about the rotor and has a winding. A switch is mounted within the housing and has a first position for allowing current in one direction through the winding and a second position for allowing current in an opposite direction through the winding. A mechanical activator is movable with or by the shaft and acts on the switch to move it between the first and second positions.