LEM unveils battery monitoring transducer upgrade for UPS designs

March 30, 2011 // By Paul Buckley
LEM has introduced the latest generation of the company’s proven Sentinel product that continuously monitors the state of health of batteries in uninterruptible power supply (UPS) systems.

The enhancements incorporated in Sentinel 3+ enable it to be fully integrated into the newest architectures of UPS, accommodating UPS design evolutions such as transformerless circuit topologies.

Sentinel 3+ is a battery-monitoring transducer that makes measurements of voltage, temperature and impedance, of cells and complete batteries, in UPS installations of all sizes up to mega-watt back-up power supplies for data centers and hospitals. Sentinel 3+ reports its measurements – on VRLA (valve-regulated lead-acid), gel or flooded stationary batteries – to supervisory systems over a dedicated communications bus, and offers a capability to assess the true state-of-health of UPS batteries while they are in service. Sentinel 3+ gives complete confidence that battery arrays will deliver their rated power when called on to do so, and identifies weak and failing cells without the need to remove them from service for cycling tests.

Designers of the latest UPS systems have exploited technology developments such as the availability of fast IGBTs (insulated-gate bipolar transistors) to reduce costs by eliminating bulky and expensive transformers from their circuit configurations. The battery packs that the Sentinel product monitors are, in consequence, operated in a floating voltage mode: the battery is subjected to higher ripple currents, and the monitoring circuitry must handle high common-mode voltages, with superimposed high-amplitude, fast transients.

LEM's Sentinel 3+ features upgraded algorithms to take account of the more challenging  measurement environment, maintaining the well-proven accuracy of the Sentinel product family, as well as improved EMC immunity and enhanced overall robustness. Sentinel 3+ delivers voltage measurements over a range of 0.9 to 16 V with an accuracy of ±0.5%; impedance measurement from 0.05 to 250 mΩ with repeatability of ±2%. Sentinel 3+ features Common Mode Transient Immunity up to 20 kV/µs with a common-mode voltage level of ±600 V, and a transient repetition rate of 20 kHz.

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