An electrical power generator for a wind turbine comprising: a generator housing, a stator at a radially outward position and a rotor in a radially inward position, wherein the rotor comprises a cylindrical ring structure arranged about a rotational axis, R, and defining a central hollow portion. The electrical power generator further comprises a rotor shroud attached to the generator housing and which extends about the rotational axis, R, wherein the rotor shroud includes a dome portion that extends into the central hollow portion of the rotor so as to protect the cylindrical ring structure of the rotor. Advantageously, the rotor shroud provides a tunnel-like surface that extends into the central hollow portion of the generator so as to prevent objects such as tools from contacting components of the rotor. The invention also relates to a method for 15 assembling such an electrical power generator with a rotor shroud.