Patent ID: 7566981

Claim:
An actuating drive for a rotor blade in a wind power installation, comprising: an electric motor; a frequency converter that includes a rectifier capable of being supplied by a power supply system; a link connected to the rectifier; a d.c.-to-a.c. inverter for feeding the electric motor, wherein the link carries a specified nominal operating voltage in a network-fed normal operation of the frequency converter; an emergency energy supply device connected to the link and including an energy store that makes available an electrical support voltage; a diode having a forward direction and being connected between the energy store and the link, the diode being situated in such a way with respect to the forward direction that the diode feeds a support current from the energy store into the link if a link voltage falls below the support voltage, wherein: the diode prevents a current flow between the energy store and the link if the link voltage is greater than the support voltage, the support voltage amounts to less than 80% of a nominal operating voltage of the link; and a charging device for the energy store, a charge voltage of the charging device is less than the nominal operating voltage of the link.