Method for operating an electronically commutated motor, and motor for carrying out a method such as this

An electronically commutated motor (ECM 20) has terminals (56, 62) for connection to a DC power source (63). It has a permanent-magnet rotor (22), also a first and a second series circuit (40, 50) in each of which a stator winding strand (30, 32) is connected in series with a controllable semiconductor switch (34, 44), which two series circuits are connected in parallel to form a parallel circuit (52). In addition to the strand-connected switches (34, 44) typically found in an ECM, in a supply lead to said parallel circuit (52), a third controllable semiconductor switch (60) controls energy supply from the DC power source (63). In order to increase motor efficiency and minimize the size of any motor capacitor required, special switching steps are performed so that electromagnetic energy, remaining in the winding(s) after shutoff of power application, is converted into motor torque, instead of being dissipated as heat.