Rotary UPS 200kVA+ : system description

Introduction

The Rotabloc Dynamic UPS system has been developed to fill a void that exists in the UPS market.

Static UPS systems are ‘price’ driven and are renown for providing a ‘blue box’ solution. Whilst offering nominal technical performance and reliability Static Systems are sensitive to non-standard loads and transient conditions. Rotary & Diesel based UPS systems, however, offer superior reliability and technical performance but with a cost penalty.

Now, however, the Rotabloc UPS with its unique energy storage system, can offer a system that bridges this ‘credibility’ gap. Whilst providing end users with the technical benefits of Rotary UPS systems it achieves a price regime more usually associated with Static UPS systems.

Design

The Rotabloc UPS system is designed to provide battery-less UPS operation during periods of utility fluctuation, short-term loss or complete failure. The unique energy storage system provides sufficient ride-through to ensure that an alternative energy source (diesel-gen set) can always be connected.

The Rotabloc energy storage system comprises four simple components. Rotor, storage drum, pony motor and exciter.

When operating synchronised with the mains the Rotabloc system acts as a synchronous compensator. In this configuration the input current supplied by the synchronous machine is in quadrature with the output voltage (VA). The machine does not absorb any active power except its limited no-load losses.

Furthermore, the network current is in quadrature with the choke voltage Vs. This voltage Vs represents the vectorial difference between the network voltage and the user voltage. In the simplified diagram shown above the choke impedance is selected to be compatible with the synchronous alternator

The Rotabloc UPS system is designed to store an energy ‘charge’ during mains operation and discharge during periods of mains fluctuation and failure.

To achieve this KST have developed the Rotabloc energy storage system. This unique, and patented, system has the ability to store substantial levels of kinetic energy in its ‘flywheel’ and make this energy available whenever the mains is unavailable.

Although ‘flywheel’ systems have been developed in the past, none has managed to store the level of energy delivered by the Rotabloc unit without, that is, recourse to non-standard components, such as special bearings, helium gas cooling, electronic power converters and high maintenance designs.

Utilising its ‘patented’ energy storage system the Rotabloc unit can store up to 120 seconds of usable energy at the rated load of the UPS output.

In practice, however, the level of energy needed is only enough to enable an alternate power source to be started. This ‘alternative’ energy source is invariably a standby diesel-generator set.

After detailed research into the standard start times for installed diesel generator sets, KST have rated the standard Rotabloc unit to provide energy for a 12 seconds period.

This enables a range of manufacturers to connect their standard diesel products to the Rotabloc system, thus creating an electrically coupled DIESEL UPS SYSTEM.