A UPS (Uninterruptible Power Supply) stores energy in the form of rechargeable batteries or kinetic energy stored in heavy, rotating flywheels. Its most basic function is to bridge the gap between your primary power source and backup. That means it must quickly respond to a loss of utility power and switch your equipment to battery or generator power without allowing any objectionable dips, spikes or brownouts to pass through.
A standby UPS is mechanically switched on and off based on an internal DC-AC inverter circuit that draws power from an internal storage battery. When incoming utility voltage dips below a set point, the UPS switches on and begins providing AC power to connected equipment through its inverter output. When power returns the UPS disconnects its inverter and connects the protected equipment to a high-quality surge protector.
Incoming utility power is alternating current (AC), but UPSes must convert that AC to direct current (DC) to charge their batteries and still deliver AC to ITE. To achieve this, the UPS has a rectifier that changes AC to DC and then an inverter that produces AC. This type of UPS is sometimes called a double conversion or full-time UPS.
Most UPSes use valve-regulated lead-acid (VRLA) batteries, but Eaton now offers lithium-ion batteries for higher reliability and lower operating costs. Both technologies are efficient and safe, but the type of UPS that is right for you depends on the size of your load and how many minutes of runtime you need.