Abstract: There is provided a wind turbine pitch drive unit comprising an electrical energy storage, a resistor, and a cooling fan arranged to provide an air flow over the resistor. The pitch drive unit is configured to discharge the electrical energy storage by: connecting the electrical energy storage to the resistor such that a current from the electrical energy storage flows through the resistor; disconnecting the electrical energy storage from the resistor when a voltage across the electrical energy storage reaches a first pre-determined threshold; and once the voltage has reached the first pre-determined threshold, powering the cooling fan with the electrical energy storage until the voltage reaches a second pre-defined voltage, thereby cooling the resistor.

Abstract: A method for the operation of a pitch system of a wind turbine with at least one rotor blade, wherein the pitch system has at least one input rectifier and at least one pitch drive, each rotor blade can be rotated around its longitudinal axis by the one pitch drive or by at least one of several pitch drives, each input rectifier is supplied with alternating voltage by a supply network, and each pitch drive is supplied with electric power by the one input rectifier or by at least one of several input rectifiers, each pitch drive is connected to an emergency power storage device, whereby each pitch drive can be supplied with electric power by the emergency power storage device that is connected to it.

Abstract: A method for the operation of a pitch system of a wind turbine with at least one rotor blade, wherein the pitch system has at least one input rectifier and at least one pitch drive, each rotor blade can be rotated around its longitudinal axis by the one pitch drive or by at least one of several pitch drives, each input rectifier is supplied with alternating voltage by a supply network, and each pitch drive is supplied with electric power by the one input rectifier or by at least one of several input rectifiers, each pitch drive is connected to an emergency power storage device, whereby each pitch drive can be supplied with electric power by the emergency power storage device that is connected to it.