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Circuit Protection Terminology

Kilobits per second (kbps)

1,000 bits per second. A measure of transmission speed.

Knee (of the demagnetization curve)

In the second and fourth quadrants of the hysteresis loop, some materials such as ferrite and rare earth exhibit a distinct �knee�, or rapid change in slope of the intrinsic curve. The location of the knee is of interest to designers.

Kool Mu (r)(Raychem)

Kool Mu (r) is a magnetic material that has an inherent distributed air gap. The distributed air gap allowes the core to store higher levels of magnetic~ when compared to other magnetic materials such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates.%0aKool Mu (r) material is an alloy that is made up of basically nickel and iron powder (approx. 50% of each) and is available in several permeabilities. It has a higher permeability than powdered iron and also lower core losses. Kool Mu (r) is require to be pressed at much higher pressure than powdered iron material. The manufacturing process includes an annealing step that relieves the pressure put onto the powdered metals which restores their desirable magnetic properties. Thus, the powdered particles require a high temperature insulation as compared to powdered iron. Kool Mu (r) performs well in switching power applications. The relative cost is significantly higher than powdered iron.

Kool Mu�(CoEv)

A magnetic material that has an inherent distributed air gap. The distributed air gap allows the core to store higher levels of magnetic energy when compared to other magnetic materials such as ferrite. This characteristic allows a higher DC current level to flow through the inductor before saturation occurs. Kool Mu� material is an alloy that is made up of basically nickel and iron powder (approximately 50% of each) and is available in several permeabilities. It has a higher permeability than iron powder and lower core losses. It must be pressed at a much higher pressure than iron powder material. Kool Mu� performs well in switching power applications. The relative cost is significantly higher than iron powder.

Laminated Cores(CoEv)

Cores constructed by stacking multiple laminations on top of each other. The laminations are offered in a variety of materials and thicknesses. Some laminations are made to have the grains oriented to minimize the core losses and give higher permeabilities. Each lamination has an insulated surface that is commonly an oxide finish. Laminated cores are used in some inductor designs, but are more common in a wide variety of transformer applications.

Laminated Cores(Raychem)

Cores constructed by stacking multiple laminations on top of each other. The laminations are offered in a variety of materials and thicknesses. Some laminations are made to have the grains oriented to minimize the core losses and give higher permeabilities. Each lamination has an insulated surface which is commonly an oxide finish. Laminated cores are used in some inductor designs but are more common in a wide variety of transformer applications.

Laminations

Supplied in stamped letter shapes such as �EI�, �EL�, �EE�, �F�, or �UI�, they are composed of silicon iron and nickel alloys. Audio and telecommunication transformers use nickel alloys, while silicon iron is generally used for line frequency power transformers.

LAN

Local Area Network- The means by which a local community of users and workgroups can share information and resources electronically. Many communications protocols are used to accomplish this, the most prevalent of which are Ethernet and Token Ring.

Last mile

A reference to the local loop, the distance between a local telco office and the subscriber, a distance actually about 0 to 3 miles (0 to 4 kilometers).

Leakage Current

Current flowing from input to output or input to case of an isolated converter at a specified voltage level.

Leakage Flux

The small fraction of the total magnetic flux in a transformer or common mode choke that does not contribute to the magnetic coupling of the windings. In a transformer with a single set of primary and secondary windings, the leakage flux is that portion of flux that is produced by the primary that does not link the secondary. The presence of leakage flux in a transformer or common mode choke is modeled as a small leakage inductance in series with each winding. It is measured at one winding with all other windings shorted.

Leakage Inductance

The inductance that does not link the primary in a coil. It is due to the leakage flux.

Leased Line

A transmission line reserved by a communication carrier for the private use of a customer.

LEC

local exchange carrier

LFM

Linear feet per minute, which is a measure of air velocity used to cool a power converter.

Life test

Reliability test in which a converter is operated (typically under accelerated conditions) over some period of time in order to approximate its life expectancy.

Lifeline POTS

A minimal telephone service designed to extend a "lifeline" to the telephone system in case of emergency, particularly when electric power is lost.

Line

Bus used to deliver power to the input terminals of a converter. Also see Bus, High Line and Low Line.

Line Code

Any method of converting digital information to analog form for transmission on a telephone line. 2B1Q, DMT, and CAP are all line codes.

Line Effect

See Line Regulation.

Line Regulation

Power supply regulation technique in which the regulating device (typically a transistor) is placed in series or parallel with the load. Voltage variations across the load are controlled by changing the effective resistance of the regulating device to dissipate unused power. Also see Series Regulator, Shunt Regulator and Post Regulation.

Line transient

See Input Transient.

Linear Material

Magnetic material that exhibits fairly constant permeability over a wide range of MMF.

Linear Power Transformer

Transformers that generally operate between 47Hz and 400Hz in power conversion, which alter the input voltage needed for the load. Linear power transformers are very inefficient.

Linear regulation

Link

Physical connection between two nodes in a network. It can consist of a data communication circuit or a direct channel (cable) connection. Also an LED signal that indicates connection has been established.

Litz Wire

Wire consisting of a number of separately insulated strands that are woven or bunched together such that each strand tends to take all possible positions in the cross section of the wire as a whole. The current through each individual strand is divided equally since this wire design equalizes the flux linkages and reactance of the individual strands. In other words, a litz conductor has lower AC losses than comparable solid wire conductors which becomes important as the oeprating frequency increases (Also see Skin Effect).

Litz Wire

From the German word �litzendraght�, meaning to consist of a number of separate strands that are woven or bunched together such that each strand tends to take all possible positions in the cross section of the wire as a whole. The current through each individually insulated strand is divided equally since this wire design equalizes the flux linkages and reactance of the individual strands. In other words, a litz conductor has lower AC losses than compared to solid wire conductors, which becomes important as operation frequency increases.

LMDS

local multipoint distribution service

Load

Electronic components/circuits connected to the output pins of a converter. The characteristics (resistance, reactance, etc.) of the load determine the amount of power drawn from the converter

Load Decoupling

Placement of filter components (typically mF capacitors) at the power terminals of the load in order to reduce noise.

Load Loss

These losses are caused by the resistance of the windings under loaded conditions.

Load Regulation

Percentage change in output voltage caused by varying the output load over a specified range (with input line, temperature, etc. remaining constant).

Local Area Transport Area (LATA)

(1)A geographic area established for the provision and administration of communications service. It encompasses one or more designated exchanges, which are grouped to serve common social, economic and other purposes. (2) Contiguous local exchange areas that include every point served by a LEC within an existing community of interest and that serve as the dividing line for the allocation of assets and liabilities betweenthe IXC and the LEC. (3) A telephone company term that defines a geographic area", sometimes corresponds to an area code.

Local Loop

Refers to the physical copper pair or loop of wire from Central Office to the subscriber.

Local sensing

Using the output terminals of the converter to provide feedback to voltage regulation circuits. Also see Remote Sensing.

Logic Inhibit/Enable

Signal (typically TTL/CMOS compatible) used to turn a power supply output on/off. Also called Remote On/Off.

Long Term Stability

Change in output voltage of a converter over time with all other factors (line, load, temp. etc.) remaining constant. Expressed as a percent, the output change is primarily due to component aging.

Low Line

Minimum value of input line voltage speified for normal converter operation.

MAC

media access control

Magnet Wire

Copper or aluminum wire with electrical insulating material applied to the surface to prevent continuity between adjacent turns in a winding.

Magnetic Energy

The product of the flux density (B) and the (de)magnetizing force (H) in a magnetic circuit required to reach that flux density.

Magnetic Flux

A contrived but not measurable concept that has evolved in an attempt to describe the �flow� of a magnetic field. Unlike electric current where there is an actual flow of electrons, a magnetic field is the result of the energy state of a series of magnetic domains. Conceptually, one could imagine that the sequential change of energy state as the result of an applied field represents �flow�.

Magnetic Lines Of Force

An imaginary line representing a magnetic field, which at every point has the direction of the magnetic flux at that point.

Magnetic Path

The route the magnetic flux �flows� in a magnetic circuit.

Magnetic Path Length

The length of the closed path that magnetic flux follows around a magnetic circuit. Ampere�s Law determines it.

Magnetic Wire

Wire used to create a magnetic field such as those in magnetic components (inductors and transformers). Magnet wire is nearly 100% copper and must be made from virgin copper. It is covered with a number of difference organic polymer film coatings.

Master/Slave Operation

Maximum Ambient Operating Temperature

The highest ambient temperature at which a circuit is expected to operate.

Maximum Device Voltage

The highest voltage that can safely be dropped across a PolySwitch™ device in its tripped state under specified fault conditions.

Synonyms: Maximum Interrupt Voltage,Maximum Voltage,Vmax

Maximum Fault Current

The rated maximum value of peak pulse current of specified amplitude and wave shape that may be applied without damage.

Maximum Interrupt Current

The highest fault current that can safely be used to trip a PolySwitch™ device under specified conditions. Typically the lower the voltage dropped across the PolySwitch™ device in its tripped state, the higher the maximum interrupt current. Maximum interrupt currents are usually shown in this Databook at the maximum voltage. It may be possible to use a PolySwitch™ device at a higher interrupt current, but each such use must be individually qualified.

Synonyms: Imax

Maximum Interrupt Voltage

The highest voltage that can safely be dropped across a PolySwitch™ device in its tripped state under specified fault conditions.

Synonyms: Maximum Device Voltage,Maximum Voltage,Vmax

Maximum Load

Highest amount of output load allowable under the continuous operating specifications of a converter.

Maximum Operating Voltage

The maximum voltage across a PolySwitch™ device under a typical fault condition. In many circuits, this is the voltage of the power source in the circuit. It may be possible to use a PolySwitch™ device at a higher voltage, but each such use must be individually qualified.

Maximum Output Resistance

The resistance of a device at a specified voltage.

Maximum Power Dissipation

An inductor's ability to handle the heat generated by operating at maximum current at an ambient temperature, expressed in Watts (W) or milliwatts (mW). This is a function of the body area of the inductor, core material used, and varies for shielded vs. unshielded.

Maximum Resistance

The maximum resistance of a PolySwitch™ device at room temperature one hour after being tripped or after reflow soldering.

Synonyms: R1max

Maximum Switching Current

The maximum current that a device switches at safely without damage.

Maximum Voltage

The highest voltage that can safely be dropped across a PolySwitch™ device in its tripped state under specified fault conditions.

Synonyms: Maximum Device Voltage,Maximum Interrupt Voltage,Vmax

Maxwell

The unit of magnetic flux in the CGS system. One Maxwell = 10-8 webers.

MCNS

multimedia cable network system

MDU

multi-dwelling unit

Mean Time Between Failure (MTBF)

Unit of measure, expressed in hours, that gives the relative reliability of a converter. MTBF data is based upson actual operating data (demonstrated) or derived per the conditions of MIL-HDBK-217F (calculated).

Metropolitan Area Network (MAN)

A data communication network covering the geographic area of a city. Often used by a CAP to carry backbone traffic in their serving area.

Minimum Load

Minimum amount of output load required on a converter in order to maintain normal continuous operating specifications. Usually associated with PWM (Pulse Width Modulation) controlled converters.

Minimum Operating Temperature

Minimum ambient temperature at which a converter will start and operate within specifications.

MLT

The mean-length-turn of wire for a core.

MMDS

multi-channel, multipoint distribution service

Modulation

Process by which signal characteristics are transformed to represent information. Types of modulation include frequency modulation(FM), where signals of different frequencies represent different data values.

Module

Encapsulated DC-DC converter.

MOM

message-oriented middleware

MPEG

moving pictures experts group

MPLS

multi-protocol label switching

MPP Core(CoEv)

MPP is an acronym for molypermalloy powder. It is a magnetic material that has an inherent distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials such as ferrite. This characteristic allows a higher DC current level to flow through the inductor before is saturates. The basic raw materials are nickel, iron, and molybdenum. The ratios are approximately 80% nickel, 2-3% molybdenum, and 17-18% iron. The manufacturing process includes an annealing step as discussed in the Kool Mu� definition. MPP stores higher amounts of energy and has a higher permeability than Kool Mu�. Cores are offered in 10 or more permeability selections. The core characteristics allow inductors to perform very well in switching power applications. Since the core can store higher energy, more DC current can be passed through the inductor before the core reaches saturation. However, the cost of MPP is significantly higher than Kool Mu�, iron powder, and most ferrite.

MPP Core(Raychem)

MPP is an acronym for molypermalloy powder. It is a magnetic material that has an inherent distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials such as ferrites. This characeristic allows a higher DC current level to flow through the inductor before the inductor saturates.%0aThe basic raw materials are nickel, iron and molybdenum. The ratios are: approximately 80% nickel, 2% -3% molybdenum, and the remaining is iron. The manufacturing process includes an annealing step as discussed in the Kool Mu (r) definition. MPP stores higher amounts of energy and has a higher permeability than Kool Mu (r)%0aCores are offered in 10 or more permeability selections. The core characteristics allow inductors to perform very well in switching power applications. Since higher energy can be stored by the core, more DC current can be passed thorugh the inductor before the core saturates. The cost of MPP is significantly higher than Kool Mu (r) , powdered irons and most ferrite cores with similar sizes (See saturation current and Kool Mu (r))

MTU

multi-tenant unit

Multifilar Winding

A winding technique in which a single turn consists of two or more strands of magnetwire operating in parallel. This reduces some of the second order effects associated with a single strand of wire, including skin effect downfalls and winding ease.

Multiplexer(MUX)

A technique that enables several data streams to be sent over a single physical line. It is also a function by which one connection from a layer is used to support more than one connection to the next higher layer. (2) A device for combining several channels to be carried by one line or fiber.