All UPSs are not created equal

08/01/1999


For first-time uninterruptible power supply (UPS) buyers, the choices can be intimidating, but there are essentially three UPS topologies, each appropriate for different applications: on-line, off-line, and line-active UPSs.

On-line UPSs use batteries to deliver power to an attached device. Batteries continually charge during normal source power. Since a battery stores dc power, an inverter in the UPS converts dc to ac. Because the inverter is in constant use, system operators are aware of UPS performance and status.

Utility records indicate 98% of blackouts last no longer than two minutes, and most on-line UPSs provide 5 to 10 min of battery backup, sufficient time to permit mission-critical equipment to operate uninterrupted. Situations requiring additional time to conduct orderly shutdowns are accommodated with additional battery capacity or standby generators.

Off-line (stand-by) UPSs must be turned on when normal source power becomes unavailable. Turning the UPS on usually is performed automatically by a monitoring circuit and relays. Unfortunately, inverter/converters most likely fail when first turned on, thus the availability of off-line UPSs cannot be monitored. Nevertheless, off-line UPSs offer cost-effective solutions for non-mission-critical applications.

Line-interactive UPSs borrow from on- and off-line topologies. During normal operation the inverter filters line current to the load and converts a dc trickle to keep batteries at full charge. When normal source power is removed, the UPSs transfer switch shifts from utility to battery output and the inverter reverses operation, converting the battery's dc to ac. Line-interactive UPSs are especially applicable in areas where power outages are rare, but power fluctuations are frequent.

Global UPS designs use the above topologies to provide wide ac-input voltage (85 to 280 V) capability to allow operation in Japan (100-V service) to Australia (250-V service), a frequency range of 45 to 450 Hz for use with domestic and international utilities, military power sources, and engine generators, and a 28 V dc input that allows operation from vehicle or dc engine generators. Global UPSs are complex and require a careful evaluation to ensure the additional complexity and cost is justified.

Intelligence helps
Today, many UPSs protect entire networks of equipment. Network-wide power protection can be represented in a simple shutdown interface, but complex networks require network communications to inform connected devices of source power condition and status.

Using Simple Network Management Protocol to communicate information including power quality, battery status, usage loads, power-related events, environmental temperatures, and UPS self-diagnostic results to other network devices. Each network device uses UPS provided information to initiate appropriate actions, including orderly shutdowns. Additionally, intelligent UPSs can monitor other vital network protection systems such as water detection, smoke and fire protection devices, and access and security controls.

Intelligent UPSs can assist is load management and power factor correction.

Visit www.manufacturing.net and search on UPS to locate over 100 suppliers of uninterruptible power supplies.

Dave Harrold, senior editor
dharrold@cahners.com

Calculating downtime

Today's lean organization structures, interactive workflow, and tight deadlines mean greater reliance on the network as a productivity tool. When the network goes down, productivity slows to a crawl...or stops altogether. Unfortunately, costs keep accruing.
Liebert's (Columbus, O.) web site at www.liebert.com includes a network downtime cost calculator that requires eight pieces of business information to calculate the impact of a network interruption.

For example:

1. Annual gross revenue:

$8,000,000

2. Number of employees:

35

* $114

3. Hours to restore data:

40

* $4,571

4. Hours system is down:

2

* $8,000

5. Number of sales per year:

8,000

6. Number of customers:

500

7. Number of sales lost:

2

* $2,000

8. Number of customers lost:

1

* $16,000

Total costs:

* $30,571

Note: * = Calculated values.






No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me