Patent ID: 7515389

Claim:
Method for the safe disconnection of an electric drive configured as a frequency-controlled three-phase crane motor, in which signals from redundant sensors, which detect the movements produced by the electric drive, are compared in an evaluation unit to a preselected limit value and the evaluation unit is used to provide the function of an end switch element and bring about a safe disconnection in the event of exceeding of the preselected limit value of the electric drive, said method comprising: redundantly detecting and redundantly comparing the signals of the sensors in evaluation units to preselected limit values, so that a redundant safe disconnection of the electric drive is achieved without the use of mechanical end switches in the event of an exceeding of the preselected limit value; and evaluating the signals of the redundant sensors at corresponding redundant evaluation units to determine if the respective signals of the redundant sensors deviate from each other, and if the respective signals of the sensors deviate from each other then disconnecting the motor by redundant safe disconnection elements; wherein the redundant evaluation units mutually monitor each other, and the motor is safely disconnected by redundant safe disconnection elements if the disconnect signals of the evaluation units deviate from each other.