DPA 250 S4 features ABB's distributed parallel architecture ('DPA'), covers the power range from 50 to 1500 kW and is specifically designed for critical, high-density computing environments such as small to medium sized data centers, commercial buildings, healthcare facilities, railroad signaling applications and airports. A 250 kW cabinet of the 'DPA 250 S4' can accommodate up to six 50 kW modules for a redundant power of 250 kW N+1. Up to six 250 kW frames and up to 30 modules can be connected in parallel to deliver 1500 kW of uninterrupted, pure power. Secure ring bus communication prevents a single point of failure in the system. The device's dual conversion mode provides a fully scalable and easy to maintain UPS and ensures that the power supply to the critical load is purged of mains noise and fluctuations. Transformerless IGBT converters, which feature a three-stage topology with interleaved controls, make the device lighter, more energy efficient and reduce cooling requirements. The UPS delivers a module efficiency of 97.6%.