This paper presents a modular configuration of a three-phase power factor corrected (PFC) arc welding power supply (AWPS) using bridgeless (BL) isolated Cuk converter. Discontinuous inductor current mode operation (DICM) of Cuk converter enables this AWPS to attain unity power factor (PF) inherently at the utility interface. In the proposed BL converter, the diode bridge rectifier (DBR) at the input side is completely eliminated thus reducing the conduction losses. The proposed modular converter configuration provides several meritorious features like single-stage power conversion by using devices with comparatively lower power ratings, ease of power expandability, etc. Moreover, quick dynamic response to load variations and inherent short-circuit current limit lead to excellent weld quality. The behavior of the power supply is examined concerning input PF, supply current harmonic content as well as output voltage and current regulation. Its behavior is investigated to verify its effectiveness for arc welding applications.