An electronically commutated motor has a rotor (108), a stator having a
stator winding arrangement (102), and a full bridge circuit (137)
for controlling the current (i1, i2) in the stator winding
arrangement (102); in the full bridge circuit (137), first semiconductor
switches (114, 130) are connected to a first DC supply lead (116)
and second semiconductor switches (132, 136) to the other DC supply lead
(122), said second switches being bidirectionally conductive of current
in the switched-on state. The motor has an arrangement (172, 198, 188) for
opening the first semiconductor switches (114, 130) and for closing the
second semiconductor switches (132, 136) during a predetermined operating
state. An arrangement (202) is provided for monitoring the direction of
the current (i1, i2) which flows in the second semiconductor
switches (132, 136) when the latter are conductive during the predetermined
operating state.
