Home > Terminology

Circuit Protection Terminology

Ganged port protection

Protection method where one circuit protection device (or output) is used to protect more than one output port.

Gauss

The CGS unit of measurement for flux density. One Gauss is equal to 1 Maxwell per cm2.

Gigabits Per Second (Gbps)

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

Gilbert

A unit of magnetomotive force in the CGS system.

GPRS

general packet radio service

Graded Cores

MPP and HF cores are graded into increments of permeability within their normal �8% tolerance. It is expressed as a percent deviation from the nominal value.

Grain Oriented

Silicon steel or other granular magnetic material that has a preferred direction of magnetization.

Ground

Electrical connection that is made to earth (or to some conductor that is connected to earth).

Ground Loop

Condition caused when two or more system components share a common electrical ground line. A feedback loop is unintentionally induced, causing unwanted voltage levels.

GSM

global system for mobile communications

Half Bridge

A dual, forward converter, using two power switches can also be called a half bridge. Power, which does not exceed the supply voltage, is delivered to the load only during half the input cycle. This design permits the use of a smaller transformer.

Half Bridge Converter

Converter topology that typically operates as a forward converter but uses a bridge circuit, consisting of two switching transistors, to drive the transformer. Also see Bridge Converter.

Half-Wave Rectifier

See Rectification.

Hall Effect Transducer

A device that produces a voltage output dependent upon an applied DC voltage and an incident magnetic field. The magnitude of the output is a function of the field strength and the angle of incidence with the Hall device.

Hard Magnetic Material

A permanent magnet material that has an intrinsic coercivity generally greater than or equal to about 300 Oersteds.

HDSL

High-bit-rate Digital Subscriber Line- Designed to be a cost-effective method of delivering T1/E1 line speeds over unconditioned copper cable, without the use of repeaters.

Headend

The source end of a coaxial cable TV system. Often, the site for signal processing equipment essential to proper functioning of a cable system.

Heat Flux

Flow rate of heat across or through a material, typically given in W/cm2

Heat Sink

Metal plate, extrusion, case, etc. used to transfer heat away from sensitive components and/or circuits. Also see Base Plate.

Henry

The unit for inductance.

HFC

hybrid fiber-coaxial

Hiccup Mode

Operating mode triggered by an output fault condition (short-circuit)in which the converter cycles on and off the duty cycle of on time to off time maintains the interenal power dissipation at a safe level until the fault condition is corrected.

High Line

Maximum value of input line voltage specified for normal converter operaton. Also see Low Line and Input Voltage Range.

High Potential Test (Hi-Pot Test)

Test used to determine whether a converter passes its miminum breakdown voltage specification. Also see Breakdown Voltage.

High Q Filters

A filter circuit that exhibits a high Q factor. It is very frequency sensitive and filters out or allows to pass, only those frequencies within a narrow band.

Hold Current

The largest steady state current that, under specified ambient conditions, can be passed through a PolySwitch device without causing the device to trip. For SiBar devices, the current at which the device resets to a high-impedance state once the surge current dissipates. See also Hold Current.

Synonyms: IH,IHOLD

Hold Current Minimum

The minimum current required to maintain the device in the on-state. For SiBar thyristors, the current at which the device resets to a high-impedance state once the surge current dissipates.

Hold-Up Time

Period of time that a converter output remains operating within specification following the loss of input power. This is a more common specificatioin for AC/DC supplies.

Host

The root of the USB architecture which provides signal/data and power (for bus-powered peripherals). In a USB application, the Host is typically within the main CPU.

Hot Plug-In

A common requriement in distributed power systems wherein the power board must be capable of being connected/disconnected from the power bus without damage. Power board components must be protected against the resultant high inrush currents.

Hot-Plug

The act of making a connection to the output port of a functioning peripheral or host. USB architecture is designed to recognize the connected function and �enable� it by providing necessary power and loading all necessary drivers.

Hub

Class of USB equipment that attaches to the Host and provides additional USB output connections for other hubs or functions. May be classified as self-powered hubs or bus-and self-powered hubs.

Humidity Aging Test

A test described in Raychem�s PS300 publication in which the resistance of a PolySwitch device at room temperature is measured before and after aging at an elevated temperature (e.g., 40�C) and high humidity (e.g., 95% RH) for an extended time (e.g., 1000 hours).

Hysteresis and Hysteresis Loss

Hysteresis means to lag behind. This is the tendency of a magnetic material to retain its magnetization. Hysteresis causes the graph of magnetic flux density versus magnetizing force (B-H curve) to form a loop rather than a line. The area of the loop represents the difference between energy stored and energy released per unit of volume of material per cycle. This difference is called the hysteresis loss.

Hysteresis Loop

A closed curve obtained for a material by plotting corresponding values of flux density for the ordinate and magnetizing force for the abscissa when the material is passing through a complete cycle between definite limits of either magnetizing force or flux density. If the material is not driven into saturation it is said to be on a minor loop.

IAD

integrated access devices

integrated circuit

ICP

integrated communication provider

Abbreviation for inside diameter.

IDSL

ISDN digital subscriber line

Synonyms: IHOLD

IHOLD

Synonyms: IH

ILEC

incumbent local exchange carriers (formerly RBOC)

Imax

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.

Impedance(CoEv)

The total resistance to flow of current, including both the AC and DC component. The DC component is simply the DC resistance of the winding. The AC component of the impedance includes the inductor reactance, which is written XL = 2π�L.

Impedance(Raychem)

The impedance of an inductor is the total resistance to the flow of current, including the AC and DC component. The DC component of the impedance is simply the DC resistance of the winding. The AC component of the impedence includes the inductor reactance. The following formula calculates the inductive reactance of an ideal inductor (i.e. one with no losses) to a sinusoidal AC signal. (Z

Incremental Current(CoEv)

The DC bias current flowing through an inductor which causes an inductance drop of 5% from the initial zero DC bias inductance value. This current level indicates where the inductance can be expected to drop significantly if the DC bias current is increased further. This applies mostly to ferrite cores in lieu of iron powder. These core materials exhibit �soft� saturation characteristics, which means their inductance drop from higher DC levels is much more gradual than ferrite cores. The rate at which the inductance will drop is also a function of the core shape.

Incremental Current(Raychem)

The DC bias current flowing through the inductor which causes an inductance drop of 5% from the initial zero DC bias inductance value. This current level indiciates where the inductance can be expected to drop significantly if the DC bias current is increased further. This applies mostly to ferrite cores in lieu of powdered iron. Powdered iron cores exhibit "soft" saturation characteristics. this means their inductance drop from higher DC levels is much more gradual than ferrite cores. The rate at which the inductance will drop is also a function of the core shape, i.e. air gap (Also see Saturation Current).

Incremental Permeability (μinc)

The permeability of a magnetic material about a specified operating point and applied magnetic field strength, especially under DC bias conditions. The incremental permeability is expressed as the slope of the B-H characteristic about the given operating point (dB/dH).

Individual Port Protection

Protection method where each output is protected by one circuit protection device (or output). For devices with multiple outputs per device, isolation is provided so that a port can respond to a fault condition without impacting the performance of the other port(s).

Inductance Factor (AL)

The inductance rating of a core in nanoHenries per turn squared (nH/N2) based on a peak flux density of 10 gauss (1 milliTesla) at a frequency of 10 kHz. An AL value of 40 would produce 400μH of inductance for 100 turns and 40mH for 1000 turns.

Inductance(CoEv)

That property of a circuit element which tends to oppose any change in the current flowing through it. The inductance for a given inductor is influenced by the core material, core shape and size, the turns count of the coil, and the shape of the coil. Inductors most often have their inductance values expressed in microHenries (μH) or milliHenries (mH).

Inductance(Raychem)

That property of a circuit element which tends to oppose any change in the current flowing through it. The inductance for a given inductor is influenced by the core material, core shape and size, the turns count of the coil and the shape of the coil. Inductors most oftern have their inductances expressed in microhenries (uH)

Inductor(CoEv)

A passive component designed to resist changes in current. Inductors are often referred to as AC resistors. The ability to resist changes in current and the ability to store energy in its magnetic field account for the bulk of the useful properties of inductors. Current passing through an inductor will produce a magnetic field, which induces a voltage, which opposes the field-producing current. This property of impeding changes in current is known as inductance.

Inductor(Raychem)

A passive component designed to resist changes in current. Inductors arc often referred to as AC Resistors. The ability to resist changes in current and the ability to store energy in its magnetic field account for the bulk of the useful properties of inductors. Current passing through an inductor will produce a magnetic field. A changing magnetic field induces a voltage which opposes the field-producing current. This property of impeding changes in current is known as inductance. The voltage induced across an inductor by a change of current is defined as: V

Initial Permeability (NO)

Permeability=u=B/H Initial permeability is that value of permeability when Bac=10gs.

Initial Permeability (μI)

The value of permeability at a peak AC flux density of 10 Gauss (1 milliTesla).

Initial Resistance

The resistance of a PolySwitch device under specified conditions (e.g., 20�C), before connection into a circuit. Devices of a particular type will be delivered with a range of resistances; therefore, a minimum value, Rmin, and/or a maximum value, Rmax, are often given.

Synonyms: Resistance,Base Resistance,Rmin,or Rmax

Input Current

Current drawn from the input power bus by a converter when operating under nominal conditions

Input Line Filter(CoEv)

A power filter placed on the input to a circuit or assembly that attenuates noise introduced from the power bus. The filter designed to reject noise within a frequency band. Typically these are low pass filters, meaning they pass low frequency signals, such as the DC power, and attenuate the higher frequency signal, which consists of mainly noise.

Input Line Filter(Raychem)

A power filter placed on the input to a circuit or assembly that attenuates noise introduced from the power bus. The filter is designed to reject lise within a frequency band. Typically these filters arc low-pass filters meaning they pass low frequency signals such as the DC power and attenuate higher frequency signal which consist of mainly noise. Band pass or low pass filters are commonly made up of inductor and capacitor combinations. (Also see Noise, Attenuation, EMI and Pi-Filter).

Input Reflected Ripple Current

AC component (typically generated by the switching circuit) measured at the input of a converter. Given as a peak-to-peak or RMS value.

Input Surge Current

See Inrush Current.

Input Transient

Spike or step change in the input to a converter. Input transient protection circuits arc used to shield sensitive components (such as the semiconductor switch) from possible damage due to transients.

Input Voltage Range

Minimum and maximum input voltage limits within which a converter operates to specifications. Often given as a ratio of high line to low line (i.e. a range of 9VDC to 18VDC is 2:1)

Inrush Current

Maximum, instantaneous input current drawn by a converter at turn on. Also called Input Surge Current.

Inrush Current Limiting

Protection circuit that limits the current a converter draws at turn on.

Institute of Electrical and Electronic Engineers (IEEE)

Professional organization that defines network standards. IEEE LAN standards are the predominant LAN standards today, including protocols similar or virtually equivalent to Ethernet and Token Ring.

Insulated Gate Bipolar Transistor (IGBT)

Power semiconductor device available for use in power conversion circuits.

Insulation Resistance(CoEv)

The insulation properties of the insulating material measured in Ohms (_).

Insulation Resistance(Raychem)

Resistance offered by an insulating material to current flow.

Insulation(CoEv)

Properly insulated transformers can withstand severe environmental conditions and remain in service for many years. The temperature of operation and the dielectric withstanding voltage (hipot) will determine the type and amount of insulation needed.

Insulation(Raychem)

Non-conductive material used to protect and separate electronic components or circuits.

Interface

(1)The point at which two systems or pieces of equipment are connected. (2) A connection between two systems or devices. A shared boundary defined by common physical interconnection charasteristics, signal characteristics, and meanings of interchanged signals.

Internal Power Dissipation

Power dissipated (as heat) within the converter during normal operation. Primarily a function of the power handling capability and efficiency of the converter. Internal power dissipation is normally given as a maximum specification that cannot be exceeded without risking damage to the converter.

International Electrotechnical Commission (IEC)

Organization based in Switzerland that sets standards for electronic products and components. IEC does not conduct any testing; however, their standards have been adopted by many of the national safety/standards agencies.

Intranet

A private network that uses Internet software and standards.

Inverter

Power conversion circuit that converts DC to AC power

Inverter Transformer

A transformer driven in such a manner that an applied DC power is converted to AC power (square waveform). Quite often the core is driven into saturation to accomplish this function.

Internet protocol

Iron-Core Coil/Transformer

Coil/transformer wound around an iron core to increase its inductance. At audio frequencies the iron core consists of laminations of silicon steel insulated from each other by varnish or shellac. At radio frequencies the core consists of powdered iron mixed in a binder which insulates the particles from each other.

Isc Max

The maximum short circuit a PolySwitch device is tested at the maximum operating voltage as specified.

ISDN

Integrated Services Digital Network- A CCITT networking standard devised to provide end-to-end, simultaneous handling of digitized voice and data traffic on the same link

Isolated Output

See Floating Output

Isolation

Electrical separation between the input and output of a converter; Normally determined by transformer characteristics and component spacing. Referring to isolation is specified in values of resistance (RISO, typically megohms) and capacitance (CISO, typically pF).

Isolation Capacitance

See Isolation.

Isolation Resistance

See Isolation.

Isolation Transformer

Transformer with a one-to-one turns ratio. connected between the a.c. power input to a piece of equipment and the a.c. line, to minimize shock hazard.

Isolation Voltage

Maximum voltage (AC or DC) that can be continuously applied between isolated circuits without a breakdown occuring. On converters, this is normally specified as input-output or input-case isolation. Minimum isolation voltage levels be maintained to meet most safety regulations. Also see Breakdown Voltage, High Potential and Isolation.

Isotropic

Having magnetic properties that are independent of the magnet orientation. Most magnetic materials are anisotropic as cast or powdered: each crystallite has a preferred direction of magnetic orientation. If the particles are not physically oriented during manufacture of the magnet, this results in random arrangement of the particles and magnetic domains, and produces isotropic magnetic properties. Conversely, orienting the material during the manufacture results in an anisotropic magnet.

ISP

Internet Service Provider

The smallest steady state current that, if passed through a PolySwitch device, will cause the device to trip, under specified conditions.

ITU

International Telecommunications Union

IXC

Interexchange Carrier- (1)A long-distance telephone company offering circuit-switched, leased-line or packet-switched service or some combination. (2) Any individual, partnership, association, joint-stock company, trust, governmental entity or corporation engaged for hire in interstate or foreign communication by wire or radio, between two or more exchanges.