L1, L2, and L3 busbars belong to the same phase, and they further split into three bars allowing the use of lower-rated fuses and contactors, as well as improving redundancy The first misconception that many make is to assume that parallel busbars share the current equally. Consider the single-phase-three-pole 400 V – 2,500 A – 60 Hz busbar assembly that terminates in a contactor, as shown in Figure 1. This division of busbars facilitates lower-rated, inexpensive. Having two busbars without gap seems illogical as it could as well have been one single busbar of larger cross section in such a case. Two smaller cross section busbars instead of one larger one are preferred to reduce the loss of current carrying capacity due to skin effect at large current. In electric power distribution, a busbar (also bus bar) is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution, transmission, or switching substations. In simple terms, a busbar is a common node where multiple incoming and outgoing circuits connect. I attached picture for better understanding.
