This is an Eaton 91PS-series 3-phase UPS power module rated at 10kW, supplied as a frame/module 'without batteries' — the battery cabinet is a separate purchase, common in larger UPS installations where battery runtime is sized independently per site. It includes an MBS (Maintenance Bypass Switch), available in either 1:1 (single UPS) or 3:1 (three UPS units sharing one bypass) configuration, which lets technicians route power around the UPS entirely during servicing without dropping the load it protects — essential for facilities that can't tolerate any downtime during UPS maintenance. This class of equipment is used in data centres, server rooms, and industrial facilities needing robust three-phase backup power infrastructure rather than a simple plug-in UPS.