UPS MAINTENANCE
RIELLO UPS IRELAND MANAGING DIRECTOR LEO CRAIG OUTLINES THE KEY ROLE CAPACITORS PLAY IN A UPS SYSTEM AND HOW PROACTIVELY REPLACING THEM CAN EXTEND YOUR EQUIPMENT’S LIFESPAN… Breathe new life into your UPS
Capacitors are an integral part of any uninterruptible power system (UPS) and are responsible for smoothing, filtering and storing energy. A typical UPS contains dozens of capacitors ranging in size from a mini drinks’ can to a tube of Pringles. These aluminium or chromium-plated cylinders contain a pair of conducting surfaces and a dielectric layer. It’s the thinness of this layer, combined with the surface area of the plates, that determines the storage capacity. Every UPS features various capacitors (AC input, AC output and DC) working together to enhance the overall power quality. However, these age over time as the electrolyte, paper and aluminium foil inside degrades physically and chemically.
“In favourable operating conditions, a capacitor has a service life of up to 10 years.”
The speed of deterioration depends on several factors, but, in general, lifespan shortens due to a combination of overuse - the more it has to filter voltage noise or transients -
Leo Craig, Managing Director of Riello UPS Ireland.
excess current or excess heat, which evaporates the solution inside the capacitor and builds up unsafe pressure. Cost of capacitor failure Did you know that alongside batteries, capacitors are the most likely part of your UPS to fail? There are several signs a capacitor might be about to fail. A service engineer could spot deformation caused by excess heat, a fluid leak or a protrusion on the valve cap, which is evidence of stress. In addition, thermal imaging picks up any increase in temperature and identifies scorched wires connected to the capacitor which are mainly caused by over-currents. Capacitors fail in three distinct ways.
Overhaul option In favourable operating conditions, a capacitor has a service life of up to 10 years. But while there is no standard age where a capacitor will fail, industry best practice recommends replacing them between years four to eight. Known as a UPS overhaul, this proactive replacement of ageing capacitors and fans helps breathe new life into your power protection system. The new parts perform better than the ageing ones, reducing your risk of a major failure occurring. It also enables your UPS to run more efficiently, which cuts your energy use and operational costs. T: +353 (0)1 6917 601 www.riello-ups.ie
Firstly, they gradually fall out of tolerance. Secondly, ‘open’ failures in which capacitors stop working but there’s little visible evidence that something has gone wrong. And finally, a ‘short’ failure with an obvious leak, sometimes accompanied by a loud popping sound. If a single capacitor fails, the rest of the set must pick up the slack, placing them under greater stress. This downgrades the UPS’ ability to filter, increasing the likelihood of problems with harmonics and noise. In a worst-case scenario, serious capacitor failure will send the UPS into bypass, leaving your critical load unprotected, posing a major fire risk.
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IRELAND’S ELECTRICAL MAGAZINE | 99
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