Patent ID: 7235940

Claim:
A rotary speed limiting device for an electric motor, comprising a current detecting device for continuously detecting a motor current of the electric motor; a nominal value setting for adjusting a torque; a control and/or regulating device which limits the motor current to a maximum value depending on the nominal value setting; a rotary speed detecting device for indirectly detecting a rotary speed of the electric motor, wherein said rotary speed detecting device determines a rotary speed as a function of values of the motor current of the electric motor and a motor voltage of the electric motor, said control and/or regulating device determining a maximum value of the motor current depending on the rotary speed determined by said rotary speed detecting device, wherein a maximum permissible torque is pre-set by an operator, wherein the operator-set maximum permissible torque comprises a sum of first and second torque components, wherein the first torque component results from kinetic energy of rotating masses and the second torque component is a function of the motor current.