Computer Maintenance Power Quality and Protection Copyright © Texas Education Agency, 2011. All...

Computer Maintenance

Power Quality and Protection

Copyright © Texas Education Agency, 2011. All rights reserved.1

External Power Problems

External power which comes from a home or office wall outlet, is the power everyone tends to take for granted; as long as it’s fine.

You may be surprised by the number of problems external power can have: Line noise Spikes Surges Brownouts Blackouts

2Copyright © Texas Education Agency, 2011. All rights reserved.

External Power Problems (Continued)

Most external power problems go unnoticed, because they are usually small enough that the computer’s power supply can deal with them (except for the blackout).

These problems however, can lead to reliability problems in your computer.

When you plug your computer directly into the wall socket, you are subjecting your computer to several problems.

Some of these problems your computer can handle, but over time, even unnoticed problems can take their toll and result in major damage



You should know the kinds of problems that the PC can experience from external power. These problems are: Line noise:

Consists of small variations in the voltage of the power line. A small amount of noise is normal. If you have your PC plugged into its own circuit (unshared

line), you should have little trouble from line noise. If your computer shares an extension cord with an

appliance (i.e., an air conditioner), line noise will soon cause some major problems. The power-regulating circuits in your power supply burn out, and

any line noise passes through to the motherboard or disk drive.



You should know the kinds of problems that the PC can experience from external power. These problems are: (Continued) Power surges:

A power spike or over-voltage happens when disturbances like distant lightning strikes, or other anomalies in the electrical supply grid, create a voltage spike that travels down the line and to your wall plugs.

The surge lasts for only a few thousandths of a second, but will cause the voltage to increase to 1,000 volts or higher.

High voltage spikes degrade the power supply. Multiple surges over time can destroy it.


External Power Problems (Continued) You should know the kinds of problems that the PC

can experience from external power. These problems are: (Continued) Brownouts:

Also known as under-voltage, is the opposite of a power surge and happens when a sudden dip occurs in the power line voltage.

It doesn’t last too long, but it can. Usually, the power level drops below normal levels for a time and then returns to normal.

They are extremely common during periods of heavy load on the electrical system (hot afternoons/cold mornings).

The reduced voltage level causes many devices to run slower than normal or malfunction in other ways.


External Power Problems (Continued) You should know the kinds of problems that the PC

can experience from external power. These problems are: (Continued) Blackouts:

Occur when the power fails completely. Problems caused are usually more frustrating than

damaging. NOTE: The fluctuation of power surrounding a blackout can,

however, harm your system. If you are in the middle of something that is not saved, or

defragging a hard drive when a blackout occurs you will certainly have problems.

More often the damage occurs when the power returns suddenly, usually in the form of a huge spike.



You should know the kinds of problems that the PC can experience from external power. These problems are: (Continued) Lightning strikes:

This spike delivers a million volts or more if it were to hit a home or office directly.

A strike even in your vicinity can result in a very high voltage spike.

A lightning strike has been known to completely destroy or melt down every thing plugged in: computers, copiers, fax machines, telephones, and more.


Protecting Against Power Problems

Several levels of protection exist to protect your computer from these external power problems.

Two types of damage can be done to the PC by electrical forces: Catastrophic:

When the device is destroyed all at once in a single event. Degradation:

When a device is damaged over a period of instances and begins to fail or has intermittent problems.



(Surge Suppressor) Most users plug their computers into a power strip

or surge suppressor. The primary component of a surge suppressor is a

Metal Oxide Varistor (MOV). The MOV protects the computer by taking the hit from

voltage spikes. The problem with MOV is that one big spike or an

accumulation of small surges over time can knock it out. Some surge suppressors have a light to indicate that the

MOV is still all right.



(Surge Suppressor) A surge suppressor reduces power problems by

absorbing spikes and surges and by smoothing out line noise (called line conditioning) Not all surge suppressors include line conditioning.

Consider two main features when choosing a surge suppressor: Clamping voltage:

The voltage at which the suppressor begins to protect the computer.

Clamping speed: The time lapse before the protection begins, or how much

time elapses between detection and protection.



(Surge Suppressor) Other things to look for:

Energy absorption: Surge suppressors are rated in Joules, which measures

their capability to absorb energy The higher the rating, the better the protection:

200 Joules is basic protection 400 Joules is good protection 600 Joules is superior protection

Line conditioning: Line conditioning capability of surge suppressors are

measured in decibels. The more decibels of noise reduction, the better the line

conditioning.



(Surge Suppressor) Other things to look for: (Continued)

Protection indicators: An LED indicates you are protected If the LED is out, get a new suppressor

Levels of protection: Surge suppressors have three levels of protection that

indicate the maximum number of watts the suppressor allows to pass through to anything plugged into it. The standard ratings are: 500 (Good) 400 (Better) 330 (Best)



(Surge Suppressor) Line conditioners filter the power stream to eliminate

line noise. Because they are usually expensive, few PC users

use a true line conditioner. They prefer to purchase this capability in other devices,

such as a surge suppressor. In the event of an electrical storm or lightning strike,

power can surge up the telephone lines as well as the power lines. When installing a surge protector, be sure it has phone line

protection.


Protecting Against Power Problems (UPS)

An uninterruptible power supply (UPS) provides a constant (uninterruptible) power stream to the computer.

Under normal conditions, it’s a surge protector that can also handle brownout conditions. When the power drops below a certain level or is

disrupted completely, the UPS kicks in and provides power for a certain number of minutes, or even hours in some cases.


Protecting Against Power Problems (UPS) (cont.)

All UPS units have two sets of circuits: One side is the AC circuit that, in effect, is a surge

suppressor. The other side is the battery and DC to AC

conversion. The batteries store a DC charge that must be

converted to AC (because that’s what the PC expects).


Protecting Against Power Problems (UPS) (cont.) Two types of UPS units are available:

Standby UPS: Operates normally from its AC side. When the power drops, it switches over to its battery backup side.

In-line UPS: Operates normally from its DC or battery backup side. The AC side is only used in the event of a problem with the battery-

powered circuits. UPS units are often confused with a standby power supply

(SPS), or battery backup, which only supplies power when none is available and has no power conditioning abilities.

Never plug a laser printer or monitor into a conventional PC UPS. These devices are not critical to the operation of the PC and draw tremendous amounts of power at startup.


Summary Slide

Introduction to external power problems Reliability problems Damage problems Line noise Power surges Brownouts Blackouts Lightning strikes

Protecting Against Power Problems Catastrophic damage Degradation damage


Summary Slide (Continued)

Protecting Against Power Problems (Surge Suppressor) Metal Oxide Varistor (MOV) Line conditioning Clamping voltage Clamping speed Energy absorption Protection indicators Levels of protection Phone line protection


Summary Slide (Continued)

Protecting Against Power Problems (UPS) AC circuit Battery and DC to AC conversion Standby UPS In-line UPS Standby Power Supply (SPS)


Computer Maintenance Power Quality and Protection Copyright © Texas Education Agency, 2011. All...

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Transcript of Computer Maintenance Power Quality and Protection Copyright © Texas Education Agency, 2011. All...