John Arbors, Jr.
Waterloo Brewing Company
401 Guadalupe St.
Austin, TX. 78701
Dear Mr. Arbors:
As we agreed two months ago, I have prepared this report for your company, Waterloo Brewing. Waterloo, at present, runs a Local Area Network (LAN), with a server and 4 dumb terminals. Currently, this system is protected with a surge suppression system, in the form of special wall receptacles, that trips a breaker if a spike occurs. There is no protection on the phone line. This report offers technical background information on an alternative power protection device designed specifically for businesses that use LANs in their day-to-day operations; that device is called an uninterruptible power supply (UPS). This report compares three of the top name brands in UPSs in a point-by point comparison and offers conclusions and final recommendations for the purchase of a UPS, as well as a glossary to help define terms that are unfamiliar.
A perfect sine-wave can become system-shocking "dirty power" without notice and can cause extreme damage to data and computers alike. Other equipment nearby can produce "noise on the line" that can wreak havoc with a computing environment. IBM recently reported in a study of power sources that a typical processor encounters around 128 power problems a month  . These problems can be caused externally by brownouts or load switches or grid problems at the utility or caused internally by subtle disturbances from sources such as copiers, flourescent lights, faxes or even vending machines. Spikes, surges, sags, gaps, as well as electrostatic and electromagnetic interference attack your delicate electrical environment on a daily basis. UPSs provide reliable continous computer-grade AC power regardless of what happens to primary power sources [1;5] .
The hardware requires that this device be capable of running the server for 15-20 minutes, so that the manager on duty has time to effect an orderly shutdown of the system, including saving the various open ledgers and reports. To protect the computer and peripherals, the UPS should include voltage regulation, protection ports for the phone line that is connected to the computer modem, protection for the terminal connections, and a low battery indicator. The size of UPS needed is 600 VA. This number is arrived at by adding up the VA ratings of all the devices and peripherals and allowing another 40% for expansion of equipment and for fault tolerance. This allows the computer load to be 60% of the KVA rating of the UPS [4;5] .
Prices. All of the models fell within the target budget with:
Since all the models fell within the target range of your budget and since they all offer the total VA needed for this project, this point of comparison will have little effect on the final recommendation.
Operating system compatibility. The operating systems supported by these UPSs are as follows:
Since all the models fell within the target range for this requirement, this point of comparison will have little effect on the final recommendation.
Server shutdown time. The times for server shutdown are as follows:
Fenton's Powerpal offers the longest time for shutdown. The optional automatic shutdown software offered by APC is of little use on the Squirrel system because of the procedures required to effect an orderly shutdown. The smaller battery packs offered by Fenton and Tsi are not capable of keeping the terminals up for more than 15 minutes. You would have to buy one for each of the terminals to boost the power at that location, and in the case of a complete blackout it would be better to perform the shutdown, and save the equipment from power sags and surges when the power comes back online. Fenton is the obvious choice for this point.
Voltage regulation. The fourth point of comparison involves voltage regulation. The specifications for each UPS are as follows:
APC and Fenton both have automatic and full-time voltage regulation. Tsi has a standby switch or inverter and only turns on when the power drops to the level of the UPS-600's low impedence switch. In some cases, this may be too late for the data in stream or the process in porgress and could result in a lack of protection in a critical area, such as in the case of lesser sags and gaps. The choices are APC or Fenton for this point.
Phone ports and terminal connections. The UPSs must also compared in terms of the phone ports and terminal connections provided for the protection of the modem and for noise suppression on the terminal lines. The phone and terminal ports offered by:
APC's terminal ports would need an additional adapter to make the port accept an RJ45 connection. Fenton offers no surge protection on the terminal lines. It is unlikely that a surge would hit a terminal first, but it's still in the realm of the possible. Tsi Power's system offers the most flexible and comprehensive coverage in this area. Of special interest is the low impedence switch on the terminal lines. This offers the protection needed if the terminal is hit with a surge before the server, the low impedence switch would shut down the terminal affected by the surge, without disrupting the operation of the server or the remaining terminals. Tsi Power is the choice for the fifth point.
Batteries and indicator lights. The options for batteries and indicator lights are as follows:
APC's hot-swappable batteries means you can change the batteries without turning off or disconnecting the UPS. Tsi Power's Battery extensions are a clincher on this point. The battery extensions are useful for systems that are planning for expansion. Remember that expansion can mean upgrading your server or adding peripherals, with this definition almost every system will experience expansion sooner or later. Tsi Power gets this point.
The following table summarizes the comparisons discussed in the preceding:
|Categories||APC's Smart-UPS||Feonton's Powerpal||Tsi Power's UPS-600|
|Price/voltage rating||$344.00/660 VA||$299.00/650 VA||$295.00/600 VA|
|Operating system||Windows 3.1||Windows 3.1||Windows 3.1|
|Time allowed for shutdown||25 minutes||30 minutes||15 minutes|
|Phone & terminal ports||Fair||Fair||Good|
|Batteries & low-battery indicator||Fair||Fair||Good|
dumb terminals. A terminal that passively serves for input and/or output but performs no local processing.
KVA. VA times 1000.
noise. More technically referred to as electromagnetic interference (EMI) and radio frequency interference (RFI), electrical noise disrupts the smooth sine wave one expects from utility power. Electrical noise is caused by many factors and phenomena, including lightning, load switching, generators, radio transmitters and industrial equipment. It may be intermittent or chronic. Noise introduces glitches and errors into executable programs and data files.
sags. Also known as brownouts, sags are short term decreases in voltage levels. This is the most common power problem, accounting for 87% of all power disturbances according to a study by Bell Labs. Sags are usually caused by the start-up power demands of many electrical devices (including motors, compressors, elevators, shop tools, etc.) Electric companies use sags to cope with extraordinary power demands. In a procedure known as "rolling brownouts," the utility will systematically lower voltage levels in certain areas for hours or days at a time. Hot summer days, when air conditioning requirements are at their peak, will often prompt rolling brownouts. A sag can "starve" a computer of the power it needs to function, and cause frozen keyboards and unexpected system crashes which both result in lost or corrupted data. Sags also reduce the efficiency and life span of electrical equipment, particularly motors.
single-phase VA rating. Volts times Amps = VA per device.
spike. Also referred to as an impulse, a spike is an instantaneous, dramatic increase in voltage. Akin to the force of a tidal wave, a spike can enter electronic equipment through AC, network, serial or phone lines and damage or completely destroy components. Spikes are typically caused by a nearby lightning strike. Spikes can also occur when utility power comes back on line after having been knocked out in a storm or as the result of a car accident. Spikes cause catastrophic damage to hardware and loss of data.
surge. A short term increase in voltage, typically lasting at least 1/120 of a second, resulting from presence of high-powered electrical motors, such as air conditioners, and household appliances in the vicinity. When this equipment is switched off, the extra voltage is dissipated through the power line. Computers and similar sensitive electronic devices are designed to receive power within a certain voltage range; anything outside of expected peak and RMS (considered the "average" voltage) levels will stress delicate components and cause premature failure.
watts-to-VA conversion. Watts times 1.35 = VA per device.
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