Power Conditioning

Where is all that Smoke coming from? Protecting equipment and data.





Power problems are the great killer of computer equipment, and often data as well. These problems include static, noise, spikes and ground faults. Because electric power is so "normal", and because it does its work silently, (and often slowly), it is rarely suspected.

What are the Problems - And why should You be Concerned

The electric power system, originally designed to power light bulbs, is quite an engineering miracle, but it is engineering on a very large scale. Insignificant events on power grid scale can be disasterous to computers and other electronic equipment. Here is a list of common problems, any of which can destroy your computer equipment:
  • Overvoltage - sustained voltages higher than normal. Overvoltage causes a computer's power supply components to overheat and die.

  • Surge - serious overvoltages that last more than a fraction of a second (or they would be spikes).

  • "Brownouts" - sustained undervoltage. If the voltage is too low for the computer's power supply to compensate, the computer can freeze or behave erratically. Erratic behavior is the worst because it can cause major data corruption on your hard disk. Hard disk drive motors may also overheat.

  • Power failures - any loss of power of more than 1/120th second. The computer simply shuts down. Unfortunately files may be open and data may be in the process of being written. This can cause major corruption of databases and other indexed files, especially on network servers where writes are cached.

  • Spikes - very high but momentary voltages. The worst spikes are from lightning strikes on the power wiring which can turn your computer into a smoking crater in a microsecond. Spikes are also caused by nearby motors and other magnetic devices when they are switched off, and some come from the power grid itself.

  • Fast Leading Edge Spikes - smaller spikes with very steep rise slopes. These are a silent, slow but effective killer of electronic devices.

  • EMI - electromagnetic noise from many common sources. Some of this may get through your computers power supply and cause mysterious hangs and other problems. The source is various electronic devices, including printers.

  • Miswiring - very common. Just because the wiring is done wrong doesn't mean stuff won't work when plugged in. It does mean, however, risk of shock and possible early failure of electronic devices.

  • Ground Faults - a distressingly common problem that can cause mysterious malfunctions and even destroyed network equipment seemingly without explanation (typically chips blown right off circuit boards).
Listed below are various devices you can use to protect your equipment from the depradations of these power problems, and what problems each is good for. (Index)

PC Power Supplies - A Hidden Troublemaker

The PC power supply itself (generally a silver metal box inside the computer) provides a degree of protection, depending on its quality. The power supply may have some spike protection and EMI filtering built in. Its job is to provide specific and very steady voltages to the computer circuitry even though the line power may fluctuate. How much fluctuation it can take depends on its quality.

We have seen many cases, especially in "cheap clone" computers, where problems of instability and freezing were due to a poor quality power supply, not the mother board or CPU. Ironically, this is a component almost never suspected when such problems occur.

UL approved power supplies (Backwards UR symbol) are generally of considerably higher quality than those with no certification, but cost $5 to $10 more. (Index)

Surge Supressors - The Good, the Bad and the Flamible

Over 80% of the "surge supressors" sold are of value only as switched plug strips, providing no meaningful protection. Some actually catch on fire if exposed to serious overvoltages (PC magazines have had to halt testing of some models because it was too dangerous).

Good surge supressors contain large capacitors and iron core coils as well as adequately sized surge diodes. These provide protection also against EMI (ElectroMagnetic Interference) and FLES (Fast Leading Edge Spikes) cheaper units simply pass through. Be prepared to pay $40 to over $100 for effective devices.

Especially if you live in a high lightning strike area also put protection on the telephone line to your modem. Your computer can be killed through this route also. Many surge devices include telephone line protection as well as power line protection.

Studies by the copy machine industry have shown copiers protected by a high quality surge/noise/spike protection device required less than 1/3rd as many service calls as those without adequate protection. The ratio is probably even steeper for computing devices, but since degradation happens over time most owners are entirely unaware of the damage until their equipment starts flaking out.

Don't be impressed by claims from some surge device manufacturers they will pay for any damage to your equipment if it is protected by one of their devices. It's ridiculously difficult, sometimes impossible to get them to pay off. (Index)

Network Protection Devices - For Ground Fault and Static

Problems from EMI (ElectroMagnetic Interference), static electricity, ground faults and multiple building grounds can arise whenever computing devices are connected by long cables. This applies both to network cables and serial cables (for terminals and pritners). Industrial buildings are particularly prone to grounding problems as their electrical systems have often been modified, sometimes incorrectly.

We had one client where, after they added an additional workstation, chips on their network cards would physically split open every 5 to 7 days. We had another client where chips were blown entirely off the network cards.

Surge and static drain devices are made to protect all varieties of serial and network cabling from problems of this kind. Contact Automation Access for pricing on devices that will fit your network needs. (Index)

Line Conditioners - Keeping the Voltge steady

In some locations, power is so unstable a Line Conditioner is required to keep line voltages within a range the computer power supply can handle. Tripp Lite seems to have almost a monopoly on these devices, with electronic models also including effective surge/noise/spike protection. We still see massive "autotransformers" in some installations but these are expensive and hard to find now. (Index)

Uninterruptible Power - Time for an orderly shutdown

A UPS (Uninterruptible Power Supply) is not an option for network servers or multiuser hosts, it is a necessity. Serious corruption of disk systems and databases can result from "unscheduled shutdowns" resulting in partial or total data loss.

Uninterruptible Power Supplies provide power from batteries for a sufficient time for your system to be shut down in an orderly manner. Properly sized, they will keep your server or host up for 10 to 20 minutes. Decent UPS units come with software that will do an unattended shutdown of your system.

In a critical installation, the UPS provides battery power sufficient to hold the computers up until the diesel generator sets can fire up and come on line. High end units are also SNMP (Simple Network Management Protocol) enabled so their status and condition can be monitored over the Internet.

Uninterruptible Power Supplies come in two varieties. "Standby" units switch your system to battery power when the line voltage falls below a certain threshold. "On-Line" units keep your system on battery power all the time, but the batteries are being recharged at the same rate power is drawn (except when there is a power failure). On-Line units are essential in situations where the power fluctuates greatly, as they provide a steady voltage output at all times. Standby units provide normal line voltage except when there is a power failure. Reputable UPS units also provide surge/spike/noise protection.

UPS units are rated in VA (Volt Amperes). A VA is similar to a Watt, but more complicated. UPS units are available from about 250 VA (nearly useless) to many kiloVAs. A modest PC server should generally have a unit providing 750 VA or so. (Index)

Line Monitors and Testers - How to know what your problems are

There are many devices designed to test power lines and determine what the problems are. These range from little blocks with three lights that, when plugged in, detect ground faults, reversed hot wire, and other serious deficiencies. Beyond these are power condition monitors with rows of lights that latch to show high and low voltage and spikes. At the top of the line are chart monitors that draw a continuous analysis of your power on adding machine tape.

Some UPS units provide power analysis outputs and have software available to display the record of power condition on your computer screen. (Index)

©:Andrew Grygus - Automation Access - - www.aaxnet.com - aax@aaxnet.com
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