True on-line, double conversion, three-phase UPS system with Softscale™ technology that provides a scalable solution to optimize data center power design. Uninterruptible power can grow from 40 to 60 to 80 kVA, from 80 to 100 to 120 kVA, and from 160 to 200kVA. The UPS may also be paralleled for additional capacity or for redundant operation.