A rotor comprises a rotor core comprising a rotational axis and a plurality of slots, a plurality of rotor bars inserted in the plurality of slots, and a plurality of holders arranged around a rotational axis of the rotor. Each holder comprises an insertion groove configured to receive and engage with an end of one of the plurality of rotor bars. An end of another rotor bar among the plurality of rotor bars is interposed between and coupled to two immediately neighboring holders among the plurality of holders.