UPS systems suitable for mission-critical applications including data centres, hospitals, defence, etc to ratings exceeding 1 MW are available. Double conversion, N+1 redundancy systems have relatively small footprints designs by utilising transformer-free IGBT conversion and inversion stages. The UPS systems are characterized by low input THD (<4.5% at full load) and high input power factor (>0.99).
Special synchronization technology allows load sharing between paralleled UPS units and N+1 redundancy. Patented methodology measures phase differences between UPS units, adjusting the voltage phase by monitoring output power so as to eliminate one UPS partially driving another.
The UPS systems use automatic battery condition monitoring, leaving a fully charged battery in rest mode for most of the time, and then applying charge current only at certain intervals. In order to charge up a fully or partly discharged battery, the charger starts at a constant current appropriate for the battery type used.
When the battery voltage reaches a set level, the operation is changed to float mode using a constant but lower voltage, thus providing an optimum recharge time. The UPS system’s battery is kept at this voltage for 24 hours until it comes to the first test point. This eliminates problems associated with the traditional trickle charge method, where batteries become subject to electrode corrosion and electrolyte dry-out, especially in standby service.
UPS systems are available from Westek Electronics .