CHAPTER 5 POWER SUPPLY, COOLING, AND PROTECTION

Introduction :
	The power supply unit supplies power to the different system components such as the motherboard and the device drives. You must protect the system from extreme temperature changes like overheating using cooling devices. You can also use a UPS to protect the system from power fluctuations.
5.1 Power Supply
	The power supply unit of the system, mostly found in the top right corner of the system case accepts the Alternating Current (AC) current from the power socket in the wall and converts the AC to the Direct Current (DC) for the system. The currents supplied by the power supply unit to the different components of the system are 3.3V, 5V, and 12V. The microprocessors and the chipsets in the system use 3.3V and 5V of electric current, while the disk drives such as hard disk drives and other removable disk drives use 12V of electric current. _ You may have to manually adjust the required power supply using switches. However, some power supply units automatically adjust the power supply voltage to the different components
	5.1.1 Functions of Power Supply
	The power supply junction supplies the electric current to the terminal as AC. However, the power supply unit of the system needs DC with some signals for the motherboard. As a result, the power supply unit of the system converts the AC to the DC for its use. The power supply unit of the system generates high-frequency signals during the electric current conversion from AC to DC. This frequency may harm the components of the system. To prevent damage to the system the power supply unit is packed in a metal box.
	5.1.2 Form Factors of Power Supply
	The form factor of the power supply represents the size and the shape of the power supply. The different form factors of the power supply unit are the PC/XT, AT, Baby AT, LPX, ATX(NLX), SFX, and WTX form factors. The power supply unit form factor must match the form factor of the system Cover Motherboard Connectors Disk Drive Connectors Power Supply Fan Power Plug Voltage Selector Switch case and the motherboard. The power supply connects to the motherboard using either the AT two 6-pin connector or the ATX single 20-pin connector.
	Personal Computer / Extended Technology (PC/XT) Form Factor
	The PC/XT power supply case is the used by the IBM PC/XT systems. The placement of the PC/XT power supply is at the top right side of the back end of the system case. This power supply case has a toggle switch, placed on the power supply unit enables you to switch the power supply unit on and off. The PC/XT also has a voltage selection switch controls the input voltage. It can accepts around 130W of power. The PC/XT system uses the AT connector to connect to the motherboard. _ The manufacturer presets the voltage selection switch for standard conditions. The user may not have to adjust it. The voltage selection switch is red in color.
	Advanced Technology (AT) Form Factor
	The AT power supply known as IBM PC/AT is placed at the top center of the back end of the system case and an up/down toggle switch controls the operation of the power supply unit. The PC/AT system uses the AT form factor of the power supply along with the AT motherboard. It accepts around 192W of power supply voltage. The PC/AT system uses the AT connector to connect to the motherboard.
	Advanced Technology Extended (ATX) Form Factor
	The ATX system uses the New Low Profile Extended (NLX) power supply, hence the ATX form factors are also known as the ATX (NLX) form factors. The NLX form factor does not have a power outlet to connect the power cord of the monitor to the power supply unit. This power supply fan draws air from outside the system and blows it inside of the system to cools the system. This power supply unit uses the ATX connector to connect to the motherboard.
	Small Form Factor (SFX)
	The SFX power supply unit has two fans to cool the whole system. This additional fan is placed on the top of the power supply. The internal fan of the SFX power supply is thermally speedcontrolled. The output of the SFX power supply unit is 90W, and is used on smaller systems that do not require a lot of power. The SFX power supply unit uses the ATX connector to connect to the motherboard.
	Workstation Technology Extended (WTX) Form Factor
	The WTX power supply unit is available in three varieties such as 460W, 610W, and 800W with a single fan or double fans for cooling the system. The WTX power supply large in size and has a powerful output so it is used in workstations. The WTX system uses the WTX form factor of the power supply along with the WTX motherboard. The WTX power supply case can also accommodate RAID bays that are used on servers.
	5.1.3 Components of Power Supply
	A power supply unit consists of different functional components and each of these components has values for the power supply unit. The components of the power supply are power switches, power connectors, and power supply fan.
	Power Switches
	The power switches are used to switch the power supply for the system on and off. The PC/XT systems have the power switch at the rear end of the system case that enables the user to switch the system on or off. The AT tower system cases has a power switch placed on the front side of the system case. This power switch uses connecting wires for connecting with the power supply unit of the system.
	Remote Power Switch
	The ATX system cases use electronic power switches and the switch circuitry connects the motherboard with this switch. It follows a soft power method that uses a power on signal from the motherboard that enables the power supply to switch the system on.
	Power Connectors
	The power supply unit provides current to the motherboard, hard disk drive, floppy disk drive, and various other components of a system using the power connectors. The PC/XT, AT, Baby AT, and LPX form factors of the power supply uses a pair of 6 wire connectors, called as AT Style connectors to connect the power supply to the motherboard. The ATX Style connectors are the power connectors for the ATX/NLX power supply.
	Molex Connector
	The disk drive power connectors use 4 wire connectors. The 4 wire connectors are available in two sizes, a large size and small size connectors. The hard disk drive, CD/DVD drives uses the larger size connectors, commonly called as Molex.
	Mini-Plug Connector
	The 3.5-inch floppy disk drive uses the smaller size connectors, called as mini-plug.
	Power Supply Fan
	Power supply fan is used for cooling the system. The power supply fan is normally located at the rear end of the power supply unit. Some power supply fans use sleeve bearings motor and some uses ball bearing motors. The power supply fan also removes the air out of the system and protects the system components from dust or dirt. A power supply fan may stop working due to the over heating of the system components or the power supply components.
	5.1.4 Installing a Power Supply
	You must install the power supply unit in the system so that you can provide power to the different devices in the system. The power supply is placed on the top right corner at the back of the system case.
	Best Practice
	1. Read the manual before starting the installation. 2. Ensure that the connectors firmly and are not loose. 3. Tie the loose wires together.
	Precaution
	1. Ensure that the power supply is compatible with the motherboard otherwise you will permanently damage the motherboard.
	Hands on exercise
	To install a power supply unit in the system : 1. Open the system. 2. Insert the power supply unit in the system case and align the screw holes of the system case with the screw holes of the power supply unit. 3. Fix the screws of the system case with the screws of the power supply unit. 4. Adjust the voltage selector switch of the power supply unit to 115V, or 220V, or 230V. _ The 115V of voltage selection is for those regions placed outside India and the 220V or 230V of voltage selection is for India. 5. Connect the motherboard connector and the disk drive connectors of the power supply unit to the motherboard and the respective drives of the system. 6. Close the system. 7. Insert one end of the power cord to the power supply unit and the other end to the power supply junction. 8. Switch on the toggle switch placed on the power supply unit. _ Ensure that the power supply fan should be facing outside the system case.
	5.1.5 Removing a Power Supply
	Before removing the power supply unit from the system, shutdown the system, and let it cool down for few minutes. This is done because a power supply unit contains capacitors that retain current for few minutes after the system is turned off.
	Best Practice
	1. Hold the power supply as you remove the last screws that attach it to the system case.
	Hands on exercise
	To remove a power supply unit from the system : 1. Unplug all the connectors from the system case. 2. Open the system. 3. Disconnect the motherboard connector and the disk drive connectors of the power supply unit from the motherboard and the respective drives of the system. 4. Remove the screws of the power supply unit from the system case. 5. Remove the power supply unit from the system.
5.2 Cooling System
	Cooling is one of the important aspects for maintaining a system. The system cools in a specific range of temperature, thus helps the hard disk and the other components of the system to work for a longer time.
	5.2.1 Temperature Limits
	The cooling temperature limit maintains the life of the hard disk. The temperature limits for a hard disk are: _ Non-Operating temperature range – The hard disk can be stored in this temperature range when it is not operating. The non-operating temperature range is from -40 degree Celsius to 70 degree Celsius. _ Minimum operating temperature – This is the lowest temperature range that the hard disk must be exposed to while it is operating. The temperature value for this range is 5 degree Celsius. If the hard disk is operated below this temperature the hard disk will be damaged. _ Maximum operating temperatures – This is the highest temperature that the hard disk must be operated in. Operating a hard disk above this temperature limit can damage the hard disk.
	5.2.2 Air Flow
	The fans placed in the system and in the power supply helps in cooling the system and these fans control the flow of the air inside the system. The air flow in the system depends on the design of the system cases. In the baby AT system case, the power supply fan blows air outside the power supply of the system. This helps in cooling the whole system along with the components of the system. In the ATX system case, the power supply fan blows the air inside the power supply of the system. This action cools the power supply and the system case. The proper flow of the air also helps in keeping the system case clean. The inward air flow of the ATX system helps in reducing the dirt intake in the system by using filters and other mechanisms. The following help to increase the air flow in the system are: _ Keep the system cover on – Cover the system with the system cover. In absence of the system cover, the excess moisture and the dust in air may affect the system components and damage the system components. _ Cover exposed expansion slots and holes – Cover all the unused expansion card slots, drive bays, I/O ports, and other unused devices with inserts and tapes. _ Use an ATX form factor system – Use the ATX form factor of the system and the power supply. Due to the flow direction of the air from the ATX power supply unit, this form factor is preferred. _ Use a large system case – A larger system case allows a better flow of the air in the system. An extra fan can also be placed inside the system case for cooling the system. _ Arrange the internal components – The system components should be properly placed on the drive bays. Each component should be placed approximately ¼ inches apart from each other. _ Keep the system clean – The system should be cleaned using a blow drier. This protects the system from air blocks due to dust.
	5.2.3 Types of Cooling System
	The system produces heat while it is functioning that can damage the internal components of the system. Cooling systems reduces the heat in the system and thus prevents the components from being damaged.
	Fans
	The system case and the system power supply case have a fan in it that helps channel air in the system case or out from the system case. This helps cool the components located inside the system case. You can also attach fans on the microprocessor to cool it. You can use the cooling devices such as the drive coolers and the bay coolers to cool down the system components. The drive coolers are designed for cooling the hard disks. A thermal conductive tape attaches the drive coolers with the hard disk drive. It also has a fan that blows air on the hard disk to cool it.
	Drive Coolers
	The bay cooler is another device for cooling the hard disks. The hard disk is placed in the bay cooler that has fans for cooling the device and is mounted in the 5.25-inch drive bay. There are internal and external drive bays, with 3.5 inch and 5.25 inch in sizes.
	Heat Sinks
	The heat sink is used to cool the microprocessor and the other chips on the system. It is a good conductor of heat and is attached to the microprocessor. It draws the heat from the processor and the air flowing over this heat sink cools the heat sink.
	5.2.4 Installing a Case Fan
	You can fix the case fan to the system with the screws or place the case fan in a plastic housing. Both the methods are acceptable when performed on a system that contains a single fan.
	Best Practice
	1. Ensure that you have spare slots and power connectors to install the fan. 2. Switch the system off before installing any components. 3. Take care not to damage the internal components of the system.
	Hands on exercise
	To install a system case fan : 1. Locate the screw holes on the fan case. 2. Line the fan screw holes with the case screw holes. 3. After you line up the screw holes of the fan and the fan case, insert the screws to tighten the fan with the case. 4. Search the fan connector on the motherboard and then plug in the power connector of the case fan to the fan connector of the motherboard.
	Plug In Power Connector to Motherboard
	_ Check the manual before plugging in the power connector to the motherboard.
	Plug In Power Connector to Motherboard
	_ Check the manual before plugging in the power connector to the motherboard.
5.3 Protecting a System using Backup Power Systems (UPS)
	A UPS supplies current to the system for about 10 to 15 minutes, for the user to shutdown the system safely when there is a blackout. This ensures that the files on the system or the system components such as the hard disk do not get corrupted due to improper shutdown. The battery of the UPS gets charged when the system is powered on and uses the stored battery current during a power failure.A system normally uses 120V current at 60Hz of power fluctuation. It can accept a slight difference in the voltage frequency. However, a major difference in the voltage frequency can damage the components of the system. A Backup Power System (BPS) is used for protecting the system from these surges. A BPS also stores current in a battery and supplies it to the system when needed.
	Form Factor
	A form factor refers to the general shape and size of the UPS. The UPS is available in the standalone model, and rack-mount model. Stand-alone models of UPS are placed on floor outside the system. The rack-mount models of the UPS are placed on the metal racks, thus saving the floor space. These models of UPS are used when a system is placed on a rack and the UPS is placed just below the system. These are used in industries and commercial applications.
	Capacity and Run Time
	The run time of a UPS is the amount of time the battery of the UPS provides electric current to the system in case of a power failure. The capacity of a UPS means the capacity of its battery to supply electric current to the system for the maximum amount of time. It also means that the ability of the circuits and the wires of the UPS to bear the load of the electric current. The model name of a UPS displays the capacity of a UPS. For example, in UPS of 650VA has the capacity of the 650.
	Power Conditioning
	A UPS supplies electric current to the system either by supplying the battery backup current or by simply supplying the electric current from the power supply junction. This ensures that if there occurs any problem with the power supply from the power supply junction to the UPS, then the battery of the UPS will be affected and not the system. It also ensures that the UPS uses its battery as the electric current source till the power problem gets solved.
	Self -Test
	The self-test feature of the UPS ensures that the UPS is functioning properly and the system is well protected. The UPS tests itself when it is turned on and then does it periodically during the week. During the self-test period of the UPS, the UPS emits some tone with a flash of light on the indicator. The self-test feature of the UPS can be controlled with the help of the UPS control software.
	Automatic Shutdown
	This feature allows the UPS to instruct the operating system to shutdown the system. For example, if you set the parameter for the battery of the UPS to supply battery current to the system until the battery reaches to 80% of its usage. As the battery level reaches 80% of the usage, your system shuts down automatically.
	5.3.2 Types of UPS
	The functions of UPS differ from one UPS to another. You must select an UPS that has the features required by you. The different types of UPS are standby UPS, line-interactive UPS, and online UPS. 121 The UPS takes the AC current from the power supply junction, suppresses the surges, filters the current, and then supplies it to the system.
	Standby UPS
	The Standby UPS remains in the standby mode until the battery current is required when there is power fluctuations or a power failure. When the power returns to normal the UPS stops supplying the electric current to the system.
	Line-Interactive UPS
	The Line-Interactive UPS keeps a track on the power supply voltage from the power supply junction to the system. If the voltage falls very low then the UPS supplies the power to the system. This is used for the small-scale servers such as Web servers, small business, or departmental servers.
	Online UPS
	The Online UPS supplies power to the system from the UPS battery at all times even when the power supply voltage is at normal levels. The batters gets charged continuously as long as it gets power from the power supply junction. When there is a power failure the UPS continues to supply power to the system till there is power in the battery.
	5.3.3 Selecting a UPS
	Power problems can affect the systems by causing you to lose stored data or damage the system components. To protect the system from sudden power problems, you should use a UPS to overcome these problems. The considered factors for selecting a UPS are load, installation location, cooling, batteries, and efficiency. _ Load - It is necessary to check the size and the type of the system that needs to be protected by the UPS. Accordingly, the power rating of the UPS can be determined for the system. The maximum power rating of a standby UPS starts from 500VA to 1.5kVA. _ Installation location - A UPS system have a noise level between 50-60dBA and releases heat while working. As a result, it needs to be placed separately and away from the work area. This factor is considered in case of an office work area. _ Cooling - When a system uses UPS for the backup power, then the cooling facility such as an air cooler should be provided for the system as well as for the UPS. _ Batteries -The batteries of the UPS are may be placed in a separate cabinet along with the UPS or may be placed inside the UPS. If a battery of the UPS gets damaged, then you must replace the batteries immediately with a replaceable battery packs. _ Efficiency - The efficiency of the UPS system will calculate the operating costs of the UPS. If the UPS works efficiently, the operating cost of the UPS will be less.
5.4 Troubleshooting
	A power supply unit is the vital component of a system and helps the system to work for a longer time. The performance efficiency of a system partially depends on the efficiency of the power supply 122 unit. However, it is after all an electronic component and may show some problems. Due to which the performance of the system may get hampered. As a result, troubleshooting the power supply problems is also an essential task for the maintaining the system.
	5.4.1 System does not start
	When you switch on the system it does not start. The power supply does not switch on and nothing appears on the monitor screen. 1. Make sure that the power connector of the system is properly plugged-in the power supply junction. 2. Check the internal connections of the system after removing the system case cover. 3. Check the connection of the motherboard connector of the power supply unit with the motherboard. 4. Check for any occurrence of the short circuit happened inside the system case. 5. Check if there is some problem with the power supply junction.
	5.4.2 Power Supply Fan does not work or emits a lot of sound
	The power supply fan is not working when the system is switched on or makes a lot of noise. 1. Shutdown the system, remove the system case cover, and clean the dirt or dust from the fan and power supply unit with a vacuum cleaner or with compressed air.
	5.4.3 UPS not Handling Power Problems
	The UPS is not handling the power problems very well and does not function when there is a blackout. The system may also automatically shut down at times. 1. Check the capacity of the UPS battery for supporting the electric current load for the system. 2. Charge the battery of the UPS if needed by reducing some load from the UPS. 3. Check the voltage selector switch placed at the back of the system case and ensure that the voltage selected is according to the region. 4. Check the connections of the motherboard and the disk drives with the power supply unit. 5. Remove any extra disk drives if not needed during the current operation. 123