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Circuit Protection Terminology

Digital transmission facility operating with a nominal bandwidth of 1.544 Mbps. Also known as Digital Signal Level 1 (D1). Composed of 24 DS-0 channels in many cases. The T1 digital transmission system if the primary digital communication system in North America.

Digital transmision facility operating at 45 Mbps bandwidth. Composed of 28 DS-1 channels in many cases. Also known as DS-3.

Tape Wound Core(Raychem)

Cores made by rolling strips of alloy iron into a toroidal shape. The metal strips have a precisely controlled thickness which are coted with a very thin insulation material to prevent the metal in the layers to make contact with each other. The finished cores have an outside coating to protect the metal layers and they are offered in a variety of material mixes. Tape wound cores are capable of storing high amounts of energy and contain a high permeability. Their major disadvantage is that they are relatively expensive when compared to other core types (Also see Toroidal Inductor)

Tape Wound Cores(CoEv)

Cores made by rolling strips of alloy iron into a toroidal shape. The metal strips have a precisely controlled thickness, which are coated with a very thin insulating material to prevent the metal in the layers to make contact with each other. The finished cores have an outside coating to protect the metal layers and they are offered in a variety of material mixes. Tape wound cores are capable of storing high amounts of energy and contain a high permeability. Their major disadvantage is that they are relatively expensive when compared to other core types.

TDM

time division multiplexing

TDMA

time division multiple access

Technischer Uberwachungs-Verin (TUV)

Organization approved for testing products to VDE standards. US-based companies often use TUV in place of VDE because they hae established facilities in the US.

Telecommunications Transformers

Also referred to as broadband transformers, these are transformers specialized for connecting a piece of equipment to the phone line or telephone network. Its function is to isolate the equipment from the phone line, improve common mode noise rejection, and match different impedances.

Telecommuter

Person who performs work at home while linked to the office by means of a telecommunications-equipped computer system.

Temperature Coefficient (TC)

The relative change of the quantity considered divided by the temperatures producing it.

Temperature Coefficient Of Inductance

(Tc of L)Is the value of inductance change as a function of temperature exposure, normally expressed in parts per million per degrees Celsius. This is a calculation comparing inductance at a reference temperature (25 degrees C, room ambient) to the extremes and other temperatures within operating range. Can be called Percent Delta L. or Temperature Stability: the lower the change the better for most applications.

Temperature Factor (TF)

The fractional change in initial permeability over a temperature range divided by the initial permeability.

Temperature Range

The ambient temperature range of the air (or other medium) surrounding a PolySwitch™ device under normal operating conditions.

Temperature Rise

The increase in surface temperature of a component in air due to the power dissipation in the component. The power dissipation for an inductor includes both copper and core losses.

Temperature, Maximum Ambient Operating

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

Termal Conductivity

Given materials ability to conduct heat, which is the time rate for heat transfer (via conduction) across a unit material thickness of 1 meter and when the temperature differential of the two opposite faces is 1 degree K.

Tesla

The MKSA (SI) unit for magnetic flux density, defined by Faraday�s Law. A Tesla represents a volt-second per square meter per turn. One Tesla is equal to 10,000 Gauss.

Test Frequency

Is the industry/military standard for testing a range of inductances. It is not intended as the application frequency. Expressed in megahertz (MHz) or kilohertz (KHz)

Test, Humidity Aging

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).

Test, Passive Aging

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., 70�C or 85�C) for an extended time (e.g., 1000 hours).

Test, Solvent Resistance

A test described in Raychem�s PS300 publication to test the durability of the markings on PolySwitch™ devices when exposed to various solvents.

Test, Thermal Shock

A test in which the resistance of a PolySwitch™ device at room temperature is measured before and after a temperature cycling treatment (e.g., cycled 10 times between �55�C and +125�C).

Thermal Conductivity

Thermal Derating

The change in the hold current and trip current of a PolySwitch™ device that takes place as there is a change in the ambient temperature of the air (or other medium) surrounding the device. An increase in ambient temperature decreases the hold current (and the trip current). A decrease in ambient temperature increases the trip current (and the hold current).

Thermal Gasket

Flexible pad or wafer with a very low thermal resistance that is put between a power module baseplate and heat sink to ensure high thermal conductivity across the junction

Thermal Joint Compound

A fluid or paste spread between the mating surfaces of a power device baseplate and a heat sink or system chassis.

Thermal Protection

Feature that shuts the converter down if the internal tempurature exceeds preset limits. Also called thermal shutdown.

Thermal Resistance

Measure of a given material;s opposition to the flow of heat. Units are in degrees C/W.

Thermal Resistivity

Measure of a material;s ability to impede the flow of heat. Typically given in degrees C T/W, where T is the material thickness and W is the power flowing through the material in watts.

Thermal Shock Test

A test in which the resistance of a PolySwitch™ device at room temperature is measured before and after a temperature cycling treatment (e.g., cycled 10 times between �55�C and +125�C).

Three-Terminal Regulator

Regulator packaged in a standard 3-terminal transistor package. These devices can be a switching type or a linear shunt or series regulator.

Time-to-Trip

The time needed, from the onset of a fault current, to trip a PolySwitch™ device. For any particular type of PolySwitch™ device, trip time depends upon the size of the fault current and the ambient temperature. The higher the fault current and/or the higher the temperature, the shorter the trip time.

Synonyms: Trip Time,TtT

Toroid

A core that has a donut shaped surface. Toroidal cores are available in many magnetic core materials. Characteristics of toroidal inductors include self-shielding due to a closed magnetic path, efficient energy transfer, high coupling between windings, and early saturation.

Toroidal Inductor

An inductor constructed by placing a winding(s) on a core that has a donut shaped surface. Toroidal cores are available in many magnetic core materials within the four basic types: Ferrite, Powdered iron, Alloy and High Flux, and Tape Wound. Characteristics of toroidal inductors include: self shielding (closed magnetic path), efficient energy transfer, high coupling between windings and early saturation.

Tracking

For a multiple output converter the parameter that gives the change in one output voltage caused by a change in the voltage level or load on another output.

Transformer

A passive device that changes voltage, current, or impedance to the required parameters. This is usually done by placing two or more windings around a soft magnetic core. Applying a voltage to the primary winding will produce a magnetic field in the core, and in turn induce a voltage in the secondary winding(s).

Transient

Spike or step change in a converter paramenter. Commonly used in describing input line and output load characteristics.

Transient Recovery Time

Time required for a converter output to return to within specified limits following a step change in output load current. Expressed as a percentage of rated value.

Transient Suppression

The use of special devices to minimize the effects of transients in electronic circuits. Transient suppression devices include the metal oxide varistor (MOV), semiconductor transient voltage suppressor (TVS) and gas tube.

Transmission Controal Protocol/Internet Protocol (TCP/IP)

A reliable, full duplex, connection-oriented end to end transport protocol running on top of IP.

Transparent LAN Service

Service offered by a provider that is used to connect LANs at geographically separated sites. "Transparent" means the connection is invisible to the user and typically runs at the same speed as the LANs.

TRI

telephony return interface

Trip

Switching of a PolySwitch™ device from a low resistance to a high resistance. In its low-resistance state, the device permits normal currents to flow in a circuit. Occurrence of a fault drives the device to its high-resistance (or �tripped�) state, and this reduces the current in the circuit to a low level.

Trip Current

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

Synonyms: IT

Trip Cycle

The tripping and resetting of a PolySwitch™ device under specified conditions.

Trip Cycle Life

The number of trip cycles that a PolySwitch™ device will undergo without failure, with failure being defined in a specified way.

Trip Time

Synonyms: Time-to-Trip,TtT

TtT

Synonyms: Time-to-Trip,Trip Time

Turn Ratio

The ratio of the primary voltage (or turns) to the secondary voltage (or turns)

Twisted Pair

Cable consisting of two 18 to 24 AWG (American Wire Gauge) solid copper strands twisted around each other. The twisting provides a measure of protection from electromagnetic and radio-frequency interference.

UADSL

universal ADSL

UDP

user datagram protocol

UMTS

universal mobile telecommunications service

Undershoot

Transient change in a converter output voltage that does not meet the lower limit of the voltage accuracy specificiation. Typically occurs at converter turn on/off or with some step change in output load or input line. Also see Voltage Accuracy.

Undervoltage lockout

Design feature that helps regulate the quality of the output voltage by turning the device OFF in response to supply voltages that fall below its UVLO level. Raychem power switches have a nominal UVLO threshold of 2.5V.

Synonyms: UVLO

Underwriters Laboratory (UL)

Independent organization that conducts safety testing of products to established standards.

Uninterruptible Power Supply (UPS)

Power supply that will continue to operate after the loss of AC input power.

USB

Universal Serial Bus interoperability standard that defines the electrical power and signal transfer requirements in computing and multi-media applications. USB power requirements define a supply and output voltage of 5V, with output currents rated at 0.5A for self-powered equipment and 0.1A output for bus-powered equipment.

UVLO

VDSL

very high bit-rate subscriber line

Verband Deutscher Elektrontechniker (VDE)

German organization that sets standards for product safety and noise emissions and test and certifies products to those standards.

Vmax

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,Maximum Voltage

VOD

Video On Demand

VoDSL

voice over digital subscriber line

VoIP

Voice over Internet protocol

Volt Microsecond Constant

The product of the voltage applied across the winding and the time for the magnetizing current to reach 1.5 times the linear extrapolation of the current waveform. This constant is a measure of the entergy handling capability of a transformer or inductor. It is dependent upon the core area, core material (including the saturation flux density of the core), the number of turns of the winding and tile duty cycle of the applied pulse.

Volt-Ampere (VA)

In an a.c. circuit, a measure of apparent power, given by: VA-EI, where E is the potential in volts; I is the curernt in amperes; and VA is apparent power in volt-amperes

Volt-Microsecond Constant

The product of the voltage applied across the winding and the time for the magnetizing current to reach 1.5 times the linear extrapolation of the current waveform. This constant is a measure of the energy handling capability of a transformer or inductor. It is dependent upon the core area, core material, number of turns, and the duty cycle of the applied pulse.

Voltage Balance

For a multiple output converter, the percentage difference in voltage level of two outputs with opposite polarities and equal nominal values.

Voltage, Maximum

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

Voltage, Maximum Operating

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.

Volume Resistivilty (Core)

The ability of a core to resist the flow of electrical current either through the bulk of the material or on its surface. The unit of the volume resistivity is Ohm-cm. Core volume resistivity becomes an issue in inductor designs where the leads/terminals come in contact with the core material. This type includes axial and radial inductors that have leads epoxied into the core. As for core materials, high permeability ferrites present the most concern as their volume resistivity is typically the lowest.%0aUnder certian conditions, a low resistive path can be realized between two inductor terminals if theyare in contact with a low resistivity core. The inductor, under these condidtions, will lose its higher impedance characteristics.

VPN

virtual private network