Online Double-Conversion
In an online double-conversion UPS, the incoming AC supply is first rectified to DC (powering the inverter and charging the battery in parallel), then the inverter regenerates a clean AC waveform that feeds the load. The load is therefore always on the inverter — there is no transfer delay when the mains fails, because the battery is already feeding the same DC bus the inverter draws from.
This topology gives the strictest isolation between input disturbances and the load, the cleanest output waveform, and zero-break transfer. The trade-off versus line-interactive designs is lower full-load efficiency (continuous double conversion costs power) and higher unit cost; modern designs (Riello’s high-frequency Pure Line, the Sentryum and SDU) close the efficiency gap with input power factor near 1 and low input THDi.
Implemented by
- Sentinel Pro — full Sentinel Pro range is online double-conversion with PF 1, THDi < 7%
- Sentinel Dual SDU — 4–10 kVA, rack/tower convertible
- Pure Line — high-frequency online double-conversion, 1–10 kVA
- Sentryum — 10–20 kVA, tower, three-phase variants
Connections
- Sentinel Pro — implements_feature, source: https://standbysystems.co.za/ups_products/sentinel-pro-700-3000va/
- Sentinel Dual SDU — implements_feature, source: https://standbysystems.co.za/ups_products/sentinel-dual-sdu-4-10kva/
- Pure Line — implements_feature, source: https://standbysystems.co.za/ups_products/pure-line-1000-10000va/
- Sentryum — implements_feature, source: https://standbysystems.co.za/ups_products/sentrym/