Uninterruptible Power Supplies: A Critical Power Play

Part 1: UPS: Standby Systems Ideal for Small Applications

Part 2: Line-Interactive UPS Offer Higher Reliability

Part 3: True Online UPS Offer Higher Power Quality, Compact Size

Part 4: Standby Online Hybrid UPS Improve Energy Efficiency

Part 5: Flywheel UPS Require Less Maintenance

Part 6: Maintenance Requirements for Uninterruptible Power Supplies

Part 7: PRODUCT FOCUS: Uninterruptible Power Supplies

Flywheel UPS Require Less Maintenance

By Greg Livengood - February 2010

A flywheel UPS uses a heavy, rotating disc to store energy and convert DC power to AC power to serve critical and sensitive electronic loads. During voltage fluctuation or interruption, a flywheel UPS acts as a power generator until stored energy dissipates.

With a ride-through time of 15-40 seconds, this UPS keeps critical loads online until utility power returns or generators come online. Managers also can opt to install flywheel UPS ahead of typical UPS battery systems to increase battery life.

Typical applications include data centers, industrial buildings, and health care facilities, and a typical size is a 60 kVA unit capable of multiple mega-volt-ampere systems connected in parallel.

Advantages include: very high energy efficiency — up to 98 percent — and low heat output; sustainability because the unit requires no battery replacement or disposal; low carbon-dioxide emissions; lower life-cycle costs; fewer maintenance requirements because the units have no batteries to maintain; and one-half the footprint of a battery-type UPS so managers can install it in most spaces without ventilation.

Disadvantages include higher initial cost and possible problems with ride-through time if standby generators do not come online in 15-20 seconds.