An electric machine includes at least one rotor module. A rotor module includes a rotor hub having a hub body, and a plurality of first protrusions and a plurality of second protrusions. One or more first protrusions include an elongated portion and a head portion. One or more second protrusions include a wedge-shaped profile. The rotor module further includes a magnetic core having a plurality of core members disposed on the rotor hub. A core member of the plurality of core members is disposed such that the head portion of the first protrusion located between the adjacent second protrusions engages with the core member, and each of the one or more second protrusions extends at least partially in a space between adjacent core members of the plurality of core members. Moreover, the rotor module includes a permanent magnet disposed in a space between the adjacent core members.