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Issue of May 2003 
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Cover Story: Power Conditioning
Buying the right power equipment

Along with a good power conditioning strategy it’s also important to purchase good power equipment. Here are some criteria and factors to consider when purchasing power equipment. by Soutiman Das Gupta

A good power conditioning strategy is a critical subset of Business Continuity Management (BCM) and allows companies to maximize business uptime for critical applications. While a UPS allows uninterrupted power, power conditioning addresses a wider scope.

"A power conditioning solution takes into account the business network blueprint, from the grid (incoming) power stage to the load (equipment requirement) stage. The solution should ideally be planned at the blueprint stage and implemented, with the rest of the cable, wiring and equipment installation to allow correct measurement at every phase," advises Shrikant Bapat, Country Champion-Uptime Solutions, Emerson Network Power (India).

And to ensure that your power conditioning solution will not let you down, it’s very essential to make the right purchases of equipment. Many organizations are unable to understand the need for a network uptime solution and hesitate from making this investment, though it may be just one percent of their IT budget. "To them our advice is that to be truly, globally, competitive, it is critical to accurately assess the cost of downtime to your business and put this in a ROI perspective," says Bapat.

Factors to consider

Here are some factors to consider while determining a power conditioning solution. There must be:

  1. An alternate source of power (backup power).
  2. UPSs that adhere to the specifications of the power equipment. It should have a bypass line connection, and include a surge diverter and a powerline filter.
  3. An Isolation transformer at the input of the UPSs.
  4. Earthing and bonding.
  5. Alternate distribution.
  6. Static switches.
  7. A SCVS - Servo Controlled Voltage Stabilizer
  8. Site and load study.
  9. A log book for battery monitoring and maintenance.

Criteria for selection of equipment

Manoj John, Industry Manager, Industrial Technologies Practice, Frost & Sullivan (India) suggests a number of criteria for selection of power conditioning equipment.

Match capacity with load requirements: The Watts ratings on hardware do not always accurately represent the amount of power it consumes. One should either measure the actual power drawn by the equipment or select a UPS with a VA rating that significantly exceeds the rating shown on the equipment.

Consider hardware and software features: For example, if the UPS is supporting a group of servers, you should use communication software which has the ability to close applications running on each server and ensure its safe shutdown.

Understand topologies: There are three types of UPS topologies- online, offline and line interactive (See story, ‘Powering up your business’). Each provides different types of advantages and disadvantages. Decide on the topology apt for your enterprise.

Vendor warranty and onsite service options: Explore all the possible warranty alternatives with the vendor to choose the one most convenient.

Compare specifications: The specifications are:

  1. The more maximum output load in the current capacity (expressed in amps and time duration), the better.
  2. The more transient voltage surge suppression capability (expressed in joules), the better.
  3. The faster output response time the better.
  4. The faster battery recharge time the better.
  5. More the number of AC outlets/sockets the better.

Battery life: Information about the specified battery life, recommended environmental conditions, and whether user-replaceable is important.

Warning systems and checks: Check for alarms or LEDs that indicate mains failure, output overloads, whether the inverter is running on UPS battery, and whether the battery charge is low.

Value offerings with high cost: If you buy a more expensive unit, get the one with software that automatically saves data, closes applications, and turns off the computer equipment in advance, before the UPS standby power goes out, following the mains failure.

Compare warranties and insurance guarantees: This is among the top reasons for customers not reaching target ROIs on IT equipment purchases. The gray market today is flourishing and tie-ups with PC manufacturers and assemblers are rampant. The only surety of quality equipment and post-sales service is warranties and insurance guarantees.

Additional features: There are UPSs in the market with modem surge protection, Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) noise filters. Consider them if these specifications and protections are of major concern for your sensitive hardware.

Soutiman Das Gupta can be reached at

Little things that make good power conditioning

  • 1. Use fuses and circuit breakers liberally. This protects the equipment, users, facilitates troubleshooting, and minimizes potentially dangerous situations.
  • 2. Power is like putting food into your body. Clean up power to reduce problems.
  • 3. Follow good grounding practices.
  • 4. For control systems, use a surge suppressor, isolation transformer, and UPS. Your control system will have fewer glitches.
  • 5. Any cables that go outside should have lightning protection.
  • 6. The more accurate the signal you are trying to measure, the more you need to do to clean your power.
  • 7. Motors and drives are the worst at generating noise. Preferably use EMI filters or at least reactors to minimize the noise.

Safety Earthing systems
Different earthing systems need to be understood before primary surge protection is implemented. The most common earthing systems are shown:

  • TN-S - A separate neutral and ground conductor are used. The ground conductor can be the metallic sheath of the power cable or a separate conductor. All exposed parts of the installation are connected to ground
  • TT - One point of the source of energy is grounded and the exposed-conductive parts are connected to independent grounded electrodes.
  • TN-C - Neutral and Ground conductors combine in a single conductor throughout the system. All exposed conductive parts are connected to it.
  • IT - A system that has no direct connection between live parts and ground. All exposed conductive parts of the installation are connected to independent grounding electrodes.
  • TN-C-S - Neutral and ground combine in a single conductor.

Pay attention to the ‘power factor’
A common mistake made when buying a UPS is looking at its ‘VA number’ (Volt-Amps) and confusing this power measurement with ‘Watts’. Watts equals Volts multiplied by Amps. So if your server or switch needs 1000 W, a UPS with 1000 VA may not be sufficient.

An electrical device is never 100 percent efficient in the way it handles power. This inefficiency is rated in a little number called ‘power factor’. It’s found somewhere in the fine print of UPS documentation.
The power factor usually ranges between 0 and 1. It’s multiplied with the VA number to get the real number of watts that should be the output of the UPS.

So if the power factor of a 1000 VA UPS is 0.7, then your UPS actually can handle a load of 700 watts. Consequently, your 1000 W server may also not need 1000 W due to its power factor rating.

Table with information about different vendors’ offerings

Company Model No. Used in Specifications Features Contact
Invensys Powerware 9315           Data Centers, Telecom switches and equipment 40–400 kVA

- Transiet response: Less than 5%
Power factor: 0.95
Dual feed inputs
SNMP capability
Power monitoring and management software compatible
Automatic step-by-step shutdown of critical hardware
Remote notification over pager, e-mail, and telephone
Intelligent input filter
Advanced Battery Management

Invensys Energy Systems Ltd.
4, Community Center,
Panchsheel Park,
New Delhi – 110017
Tel. 011-6499414-8
Fax. 011-6499419
Powerware 9340 Data Centers, Server Farms, Broadcasting services 80-140 kVA

- Output: 380-415 V (selectable)
Backup Time: 5-45 minutes (extendable upto several hours)
Overload capability (inverter): 110% for 10 min, 125% for 1 minute, 150% for 10 sec
Power factor: 0.7-0.9
Automatic step-by-step shutdown of critical hardware
Advanced Battery Management

Powerware 9305 Server farmsIndustrial automation 7.5 – 60 kVA

- Output: 220-480 V (selectable)
Backup time: 7-18 min
Overload capacity (inverter): 101-110% for 10 min, 111-125 for 1 min, 126-150 for 30 sec
Power Factor: 0.96
Advanced Battery Management

APC Symmetra Data centers, Server farms Scalable to 16 kVA

- Output: 220-2406000 VA
Backup at full load : 5.2 minutes (11200 W)
Backup at half load 17.1 minutes (5600 W)
Built-in automatic bypass
Hot Swap Batteries
Power expansion capability
Battery recharge time: 3 hours
Built-in Web/SNMP management

APC, IndiaBuilding No 6,
1st Avenue, Indiranagar,
Adyar Chennai,
Tamil Nadu 600 020
Tel. 044-24450900/0556
Silicon Data centers, server farms, communication equipment Scalable to 150 kVA

- Input frequency: 50/60 Hz
Built-in Web/SNMP management
200% overload capability
Built-in static bypass switch
Uses external battery system

Emerson Network Power Liebert 3 phase UPSsSeries 600 – 60 HzNpower – 60 HzSeries 300 - 60 Hz Facility-wide networks, medical equipment, industrial processes, server rooms 65 – 1000 kVsA

- Critical bus MTBF in excess of one million hours, based on actual field experience with more than 1300 systems
ASICs (Application-Specific Integrated Circuits) and IGBTs (Insulated Gate Bipolar Technology) enhance system reliability
Units are compact and quiet
Full-featured monitoring and alarm systems are displayed in easy-to-read text and graphics on a large LCD monitor
High energy efficiency design saves money on operating costs

Emerson Network Power
(India) Pvt. Ltd.
Plot No. C-20, Road No. 19
Wagle Industrial Estate
Thane (W),
Tel. 022-2580 7108/2388
Fax. 022-2582 8358,2580 0829

Transfer SwitchLiebert Smart Switch - 60Hz Facility-wide networks, medical equipment, industrial processes, server rooms Upto 400/230 (3 phases)

- Fast switching between two AC power sources
Manual and automatic transfer capability
Selectable preferred input source
Integral maintenance bypass to both input sources
Hot-swap electronics

DB Power UPS Systems Server rooms, communication equipment, industrial equipment Upto 120 kVA

- High conversion efficiency
Sinewave control
High frequancy Inverter using IGBT
Precise and accurate output voltage control
Wide input supply range
Efficient battery charging

DB Power Electronics Pvt Ltd.,
DB House, Mundhawa Road,
Pune 411 036, Maharashtra,
Tel. 9520 - 670775, 670091, 671858
Fax. 9520 – 672374
E-mail: db.pune@dbelectronics.

* The features mentioned in the table are based on brochures and inputs provided by respective vendors. Network Magazine recommends IT Managers to conduct their own conclusive tests before making a buying decision.

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