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Glossary - Computer Power Supplies
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Used to indicate that voltage or current in a circuit that is alternating in polarity at a set frequency, most often 50 or 60 Hz.
UL, CSA, and TUV are safety agencies that test specifications such as component spacing, HI-pot insulation, leakage currents, circuit board flammability, and temperature rating.
An AMPERE or an AMP is a unit of measurement for electrical current or rate of flow of electrons (coulombs per second) through a wire. If a group of electrons whose total charge is 1 coulomb passes a point in a conductor in 1 second, the electric current is 1 ampere. Its mathematical symbol is "I". In an AC power system, current (AMPS) is delivered to a load through a wire called the "hot" wire and returns through a wire called the "neutral" wire.
An industry body that publishes standards, such as standards developed by the IEEE.
http://www.ansi.org
The CE-marking is a European Union regulatory community sign. It symbolizes the compliance of the product with all essential requirements relating to safety, public health, consumer protection.
http://www.eurunion.org/
This is a European Community standard specifying the limits of radio frequency emissions which appliances and other electrical equipment are allowed.
This is a Canadian government organization that evaluates the safety of electrical equipment.
http://www.csa.ca/
The objective of D.O.C. from FCC: The FCC seeks to determine the standards, test procedures, and equipment authorization requirements that should be applied to computers as well as to CPU boards, power supplies, and enclosures used in personal computers in order: 1) to reduce regulatory burdens on computer manufacturers; 2) to remove impediments to flexible system design and construction techniques for computers; and, 3) to reduce the potential for interference to radio services by improving FCC’s ability to ensure that personal computers comply with FCC’s standards.
CPU boards, power supplies, and enclosures designed for uses in computers are proposed to be included under FCC’s standards and equipment authorization requirements. These components, which were not previously subject to FCC’s rules, will be included under an equipment authorization procedure similar to FCC’s verification procedure with the addition of a Declaration of Conformity that would be included with each product marketed.
In addition, FCC proposed to permit any party to assemble computers from authorized CPU boards, power supplies, and enclosures without further testing provided the instructions accompanying the components are followed during assembly. Computers assembled in this fashion would also be accompanied by a Declaration of Conformity.
Alternatively, the computer may be assembled using unauthorized components provided the resulting system is tested and accompanied by a Declaration of Conformity. While the measurement data, where required, must be retained by the responsible party, there is no requirement to file an application with, and obtain authorization from, the Commission prior to marketing or importation.
The rules permit manufacturers and suppliers of personal computers and personal computer peripherals to put a product on the market after testing it to ensure compliance and including a "Declaration of Conformity" ("DoC") in the literature furnished with the equipment without having to submit an application for equipment authorization and await FCC approval. Ref.: FCC 95-46 [10 FCC Rcd 8345 (1995) (ET Docket No. 95-19)
Ease of Use PC: this is an initiative proposed by the computer industry to produce personal computers that allow for the following: faster out-of-box setup, simpler operation for first time users, simpler upgradeability and increased reliability. These computers are meant to attract more first-time users with little or no computer experience.
The ratio of output power to input power expressed as a percentage.
EMI usually refers to unwanted electrical noise present on a power line. This noise may "leak" from the power lines and affect equipment that isn't even connected to the power line. Such "leakage" is called a magnetic field. Magnetic fields are formed when unwanted noise voltages give rise to noise currents. Such noise signals may adversely affect electronic equipment and cause intermittent data problems.
EMI protection is provided by placing noise filters on the AC power line. The filter reduces the noise voltage on the protected line, and by doing so also eliminates the magnetic fields of noise generated by the protected line. Noise signals that act over a significant distance are called RFI (Radio Frequency Interference). Equipment power cords and building wiring often act as antennas to receive RFI and convert it to EMI.
Electromagnetic interference (EMI) is the noise generated by the switching action of the power supply. Conducted EMI, that portion reflected back into the power line, is normally controlled with a line filter. Radiated EMI, that portion which is radiated into free space, is suppressed by enclosing the circuitry in a metal case. The FCC governs conducted and radiated emission levels.
Airflow in cubic feet per minute. A 100% increase in airflow will reduce system operating temperatures by 50% relative to ambient. For each 10°C (18°F) reduction, the life of the system is doubled. (Arrhenius equation)
The U.S. Federal Communications Commission specifies the maximum amounts of conducted noise signals (EMI) and radio frequency interference (RFI) that computer equipment is permitted to generate in Part 15 of the FCC Rules and Regulations. These limits are set in order to prevent computer equipment from interfering with the operation of radio and television receivers.
Two different limits have been set, depending on the typical application and marketing of the computer equipment. The class "A" FCC limits are for equipment intended for use in commercial and industrial environments. The more stringent class "B" limits are for residential environments where TV and radio interference is more of a problem. Most personal computers are required to meet the class "B" limits since they are often sold for home use.
Sale of such equipment requires that the manufacturer receive a FCC CERTIFICATION letter and registration number. Larger mini-computers and networking equipment are only required to meet class "A" because they are sold for commercial use. Compliance with the FCC class "A" limit need only is verified by the equipment manufacturer.
http://www.fcc.gov
A statement of compliance with U.S. FCC class "B" limits for radio frequency emission, which is issued by the FCC and accompanied by a FCC "registration" or "ID" number. Certified equipment must be marked with the ID number. Personal computer equipment marketed to the residential user must be FCC certified.
Equipment, which has been tested by either the manufacturer or an independent laboratory, found to be in compliance with the FCC class "A" limit for emission. Computer equipment that isn't required to be FCC CERTIFIED is required to be verified to the less stringent class "A" limit. Equipment, which may be verified, includes mini-computers, network file servers, and other network equipment.
A software program that is stored in semiconductor memory, such as read only memory (ROM) integrated circuits. Such programs are often embedded in hardware systems for control applications.
FlexATX: a new addendum to the microATX form factor. This new mainboard (7.5" x 9") form factor uses all of the same high performance of microATX, but allows for use in a much smaller space. It has no slots, no connectors and a highly integrated design. 'Flex' refers to flexible and this new form factor has the following goals in mind: leverage benefits of legacy removal, higher feature integration, more reliable and allows for more consumer look and feel consideration in smaller PC enclosure designs. This reduced chassis size improves the aesthetic value for the end-user and is intended to promote higher satisfaction with system ownership. For more info check out Intel's http://www.teleport.com/~ffsupprt/.
Electrical ground in an AC power system is a wire that is connected to the earth, hence the name "ground". The reason for such connection stems from the need to protect users of electrical equipment from shock hazards. Power is delivered to the utilization site using a pole mounted or other type of transformer. The output of such a transformer consists essentially of two lead wires, with the utilization voltage available between the leads. For a variety of complicated reasons involving safety, one of these transformer lead wires is connected to the earth using a copper bar driven into the ground.
From this ground connection, two wires are taken to the power utilization point. One of these wires is called the "safety ground" or "green" wire and the other is called the "neutral" wire. The ungrounded lead from the transformer is also taken to the utilization point and is called the "hot" wire. These three wires together (hot, neutral, and safety ground) make up the connections found on a typical office power receptacle. The safety ground wire appears to be redundant since the neutral wire is derived from the same point. In fact the safety ground wire isn't needed as evidenced by the large number of electrical appliances which only use only two (hot and neutral) prongs.
In electrical equipment which has a safety ground connection (as evidenced by a three prong plug), the safety ground is always connected to any exposed metal parts of the equipment. The purpose of this connection is to prevent any exposed part of the equipment to become energized with a hazardous voltage in case of a wiring fault inside the equipment. In computer equipment, computing circuits and mainboards are electrically connected to the chassis and therefore to the safety grounding wire.
The time period, following a loss of input power, that a power supply's output will remain within specified limits. Adequate hold time keeps the computer running during the transfer time required by a UPS unit.
It’s an international organization that writes standards for safety for electrical and other equipment. Many IEC standards were adopted from the German VDE, which was the main historical standards-writing body in Europe. One goal of the IEC is to harmonize differing standards between European countries to facilitate free trade. The U.S. Underwriters Laboratories (UL) and the Canadian CSA are members of the IEC.
http://www.iec.ch
A professional society and standards writing body for the U.S. Electronics industry.
http://www.ieee.org
A current higher than the nominal steady state value that is drawn by a device when initially energized or activated.
Legacy-Free: According to Intel, "legacy is defined as technology for which a feasible replacement exists." The specs of the ideal legacy-free PC's of the near future will have any combination of the following "pruned away" features to allow for room for better technological solutions: floppy drive, PS/2, ISA slots, PCI slots, Parallel and Serial Ports, standard height power supplies, etc.
The change in output voltage due to variation of the input voltage with all other factors held constant. It is expressed as a percent of the nominal output voltage. A power supply with tight line regulation delivers optimum voltages throughout the operating range.
The change in output voltage due to the output load varying from minimum to maximum with all other factors held constant. It is expressed as a percent of the nominal output voltage. A power supply with tight load regulation delivers optimum voltages regardless of system configuration.
Mean Time Between Failures. A measurement of the relative reliability of a power supply based upon actual operating data or calculated according to MIL-HDBK-217.
This is an organization that sets standards in the United States for electrical equipment including circuit breaker boxes, wiring, and electrical connectors.
Acoustical noise in dB(A) at 1 meter. Logarithmic scale. Each 3dB reduction represents 50% less noise. Issues include the pitch and speed of the fan blades, the hub size, the venturing depth, the bearing quality, and the layout of the power supply components.
The range of ambient temperatures within which a power supply can be safely operated.
The minimum and maximum input voltage limits within which a power supply will operate to specifications. A power supply with a wide input range is recommended when the line voltage is subject to brownouts and surges.
The maximum current which can be continuously drawn from the output of a power supply. PC motherboards and expansion cards draw 5 volt current. Drive motors draw 12 volt current.
A circuit that protects the power supply and computer from excessive current, including short-circuit current.
A circuit that shuts down the power supply if the output voltage exceeds a specified limit.
A delay circuit used to initialize the computer and provide a logic signal upon low line voltage.
It is a technology through which several physical storage disks are grouped into an array that appears to an operating system as one or more physical devices. RAID technology, when applied to storage disks, allows the RAID array drives to be configured into a variety of data configurations, which provide varying levels of data integrity protection and storage capacity.
This is electrical noise which is present in communications or computing equipment that results from some parts of the equipment or attached wiring acting as a radio antenna. Under certain conditions the amplitude of this noise may be large enough to disrupt communications or cause computing errors.
The magnitude of AC voltage appearing superimposed on the DC output, specified in peak to peak volts or expressed as a percent of the nominal output voltage. A power supply with clean DC output is essential for computers with high-speed processors and memory chips.
It is the square root of the average value of the squares of all the instantaneous values of current or voltage during one-half cycle of an alternating current. For a sine wave, the RMS value is approximately equal to 0.707 times the peak value of the waveform. RMS is also called the effective value.
The time required for the output voltage to return within the regulation envelope following a 50% load change. A power supply with quick transient response will reduce the risk of read/write errors during access.
TÜV is a safety-testing laboratory with headquarters in Germany. TÜV can test products for compliance with IEC or VDE requirements. Products that have the TÜV insignia have been tested by TÜV for compliance with applicable standards for sale in the European market.
http://www.tuvps.com
This private organization was originally founded as a result of the need for insurance companies to help consumers choose safe electrical and safety equipment. UL evaluates equipment submitted to them by the equipment manufacturer using standards, which UL has written for the equipment category. Equipment, which is evaluated and found to meet the safety requirements, is either UL Listed or UL recognized. Many insurance companies and local electrical codes in the U.S. require that installed electrical equipment be UL Listed.
http://www.ul.com
This is a widely used term that is technically not correct. The correct terms are UL LISTED or UL RECOGNIZED.
UL grants this form of approval to equipment that will be user installed or operated and that is found to meet the safety requirements of the applicable UL standards. If a product is UL Listed, then it must be marked with the UL symbol.
This is a form of formal approval granted by UL to devices that are not used as free standing equipment on their own, but are to be installed into some other system by a manufacturer, electrician, or possibly by an end-user.
This is a form of power measurement. For AC power systems, the watts rating is the volts rating multiplied by the amps rating multiplied by the POWER FACTOR. Watts represent actual delivered energy. In a typical AC power system, some of the Amps delivered to the load do not deliver energy to the load.
(Source PCPower/Cooling and Enlightcorp)
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