Switchboard Panel Adapter

It has nothing to do with control supply. You see! In either the incoming panel or the outgoing panel, the cable is terminated to the terminals at the back (may be at the bottom of the switchgear) and the top terminal of the switchgear is connected to the panel bus bars. But, in bus coupler there is no incoming or outgoing cable connections. The buses have to be coupled and as such both the incoming and outgoing terminals of the bus coupler have to be connected to the panel bus only. The confined space of the bus coupler switchgear panel would not permit this bending & routing of bus bars with required clearances to be maintained too. So, you provide a dummy panel nearby the bus coupler panel whose empty space is used to bend/route the coupling bus bars. As this panel is used to "Adapt" the bus bars to our requirements, this panel is called the "Adapter Panel". Hope it is clear now.