Information from Eaton Corporation:
Straight talk about capacitors in your UPS What they are, what they do, why they’re essential in your UPS — and the importance of proactive maintenance for these humble and often overlooked components.
Executive summary Capacitors are fairly simple devices, ranging in size from a thimble to a soda can, that smooth out fluctuations in electrical voltage. A typical UPS contains a dozen or more different types and sizes of capacitors — small ones that smooth out the power supplied to the UPS processor (its on- board intelligence), and large ones to regulate the power that flows to protected equipment. Like batteries, capacitors degrade over time. A typical capacitor might be rated by the manufacturer for, say, seven years of round- the-clock use, but could potentially deliver up to 10 years of useful life under favorable operating conditions.
When a capacitor fails, you might not see any visible effects, but other capacitors will have to take over the workload, which will shorten their useful lives. In many cases, a capacitor failure triggers the UPS to switch to bypass mode, during which it can’t protect downstream loads. To maximize the performance and reliability of your UPS, treat capacitors as the perishable commodity they are, and plan on replacing them at or near the end of their rated service life. Eaton® customer service engineers can diagnose the condition of the capacitors in UPSs and perform a full or partial replacement of capacitor banks, if necessary, to maintain UPS performance up to factory specifications. Proactive attention to this often-overlooked element of UPS architecture — the humble capacitor — can extend the value of the UPS system that protects your critical electronic systems.
A system load with a low P.F. will draw more current than a system with a higher P.F.. A system designer considers the following: A Low P.F. draws a higher internal current and the excessive heat generated will damage and/or shorten equipment life • Increased reactive loads can reduce output voltage and damage equipment sensitive to reduced voltage • Low P.F. requires equipment to be constructed heavier to absorb internal energy requirements • Low P.F. will result in a more expensive system with equipment able to absorb internal loads and larger load requirements • A system designer looks to increase P.F. to lower system costs, increase reliability and increase the system’s life cycle • Utilities will charge a higher cost to industrial and commercial clients having a low P.F.