Patent ID: 7650786

Claim:
An apparatus for monitoring the rotational speed in a wind energy plant, with a rotor shaft ( 14 ) which is driven by a rotor and runs out into a gear unit ( 16 ), and with a generator shaft ( 22 ), which connects an output shaft of the gear unit ( 16 ) with a generator/converter unit ( 24 ), characterized by a first rotational speed detection unit ( 26 ) on the rotor shaft ( 14 ) and a second rotational speed detection unit ( 34 ) on the generator shaft ( 22 ), wherein each rotational speed detection unit ( 26 , 34 ) has at least two rotational speed sensors working independently from each other, an analyzing unit ( 32 ) for the rotational speed, to which measured signals ( 28 , 30 , 36 , 38 ) of the rotational speed detection units ( 26 , 34 ) are applied and which generates an error signal for a rotational overspeed when a certain maximum value for the rotational speed is exceeded, and further characterized in that the analyzing unit ( 32 ) for the rotational speed compares the measured values ( 28 , 30 ) of the first rotational speed detection unit ( 26 ) with the measured signals ( 36 , 38 ) of the second rotational speed detection unit ( 34 ), taking into account a gear ratio, and generates an error signal for a shaft defect at a deviation of the rotational speed values for at least a predetermined threshold value.