1 Confidential and Proprietary to Littelfuse, Inc. © 2005 Littelfuse, Inc. All rights reserved....

1Confidential and Proprietary to Littelfuse, Inc. © 2005 Littelfuse, Inc. All rights reserved.

Telecom WIA Training

Training Agenda

1. Fuse Definition and Telecom Circuit Protection Needs

2. WIA Fuse Characteristics and Device Physics

3. WIA Fuse Telecom Application Protection Examples

4. WIA Fuse Telecom Application Product Selection

5. Littelfuse WIA Fuse Product Road Map

6. Telecom WIA Fuse Technology Challenges



Section 1Section 1 Fuse Definition and Telecom Circuit Protection Needs• Fuse Definition

– A fuse is a calibrated, intentionally weak link in an electrical circuit that provides over-current protection.

• Circuit Protection Needs in the Telecom Segment– Lightning– ESD– Inductive– Short Circuit/Power-Cross

• Fuse Technology for Telecom Overcurrent Circuit Protection – Elimination of series line resistance enabling longer loop lengths– Precise longitudinal balance allowing better transmission quality

• Typical Telecom Test Standards– ITU K.20 K.21– Bellcore GR-1089 – UL 60950

• Typical Fuse Test Standards– IEC 60127– UL 248– MITI


Fuse Definition and Telecom Circuit Protection

Fuse Definition – A fuse is a calibrated, intentionally weak link in an electrical circuit.

– Fuses function by reacting to the heat generated from excessive current flow. Once the fuses I2t rating is exceeded, the center conductor opens.

– A fuse is used to prevent fires and overheating when something goes wrong with electrical equipment. This can be the result of an accident, such as unintentional contact between power and the telephone line, an improper connection/installation, poor maintenance work, or a vandalism.

– A fuse is intended to operate before a catastrophic event occurs and can create a safety hazard. Electrical components such as capacitors, transformers, resistors, etc., can fail due to a manufacturing defect or old age, and could draw an excessive amount of current and catch fire.

– A fuse does not prevent a fault from occurring, but will operate quickly to prevent further damage occurring or the equipment becoming a safety hazard. The fuse can also limit the extent of the damage to a small portion of the equipment making repairs less costly

– IEC, UL, MITI, and CCC standards all provide definitions and requirements for fuses. For example, IEC-127 gives specific dimensional requirements and also specifying a series of fuse tests.



Circuit Protection Needs in Telecom Systems

– Thunderstorms around the world deliver 8 million lightning flashes every day. Peak current in lightning discharges range from a few KA to many hundreds of KA. Induced currents from indirect strikes range from 10A to 20KA.

– ESD results from the build up of electrical charge, when two non-conductive materials are brought together then separated. The potential between a human body & an object can exceed 35,000 volts. An ESD event can occur to the telecom system or portable devices through human contact and usage of the telecom devices.

– Inductive Load Switching is caused when an inductive load is interrupted. It occurs in factory/industrial environments where motors and relays (inductive loads) are turned on and off.

– Short Circuit or Power Cross events can occur due to human error (such cutting a phone and power line simultaneously during construction) or natural disaster such as hurricane, thunderstorm.

– One or a combination of the above threats can have obvious adverse effects on semiconductor/IC devices, electro-mechanical contacts, wiring insulation, etc., to cause interruption of telecom equipment operation, telephone service, and even fire.



Fuse Technology for Telecom Overcurrent Circuit Protection

Telecom equipment should be protected from overcurrnent conditions using either PTCs, fuses, power/line feed resistors, or flameproof resistors.

– A Fuse is a series element placed in front of the overvoltage protector on either Tip or Ring for metallic applications and on both Tip and Ring for longitudinal applications. Due to their stability, fuses are one of the most popular solutions for meeting AC power cross requirements for telecommunications equipment.

– Littelfuse Telecom WIA Fuses are designed to only interrupt a circuit when extreme fault conditions exist and, when coordinated properly with an overvoltage protector, offer a very competitive and effective solution for transient immunity needs. Advantages include:

• Elimination of series line resistance enabling longer loop lengths

• Precise longitudinal balance allowing better transmission quality

• Robust surge performance which eliminates costly down time due to nuisance blows

• Greater surge ratings than resettable devices, ensuring regulatory compliance

• Non-degenerative performance

– Telecommunication equipment best suited for a fuse is equipment that requires surface mount technology (and is thus sensitive to transients), accurate longitudinal balance, and regulatory compliance without the use of additional series line impedance.



Telecom System Test Standards

SwitchSLICMDF

UndergroundCable

OverheadCableStreet

Cabinet &SLIC (if on

DLC system)

NetworkInterfaceDevice(NID)

CustomerPremise

Equipment(CPE)

Central OfficeSubscriberPremises

DDF

Outside Plant

YD/T993ITU-T K.21FCC P 68UL 60950

YD/T993ITU-T K.21FCC P 68UL 60950UL 497

YD/T1082ITU-T K.45GR 1089UL 60950UL 497

YD/T 694 or YD/T 940ITU-T K.28GR 1089UL 60950UL 497

YD/T950ITU-T K.20GR 1089UL 60950

ToPSTN

Trunk Line (T1, T3, HDSL, etc.)



WIA Fuse Standards– IEC 127 Specification

• 5 BASIC GATES– HOLD 1.5In 60 MINUTES– OPEN 2.1In 30 MINUTES

(2MINS T )– OPEN 2.75In VARIES

T/F HBC/LBC– OPEN 4.0In VARIES

T/F HBC/LBC – OPEN 10In F<20mS

T>20mS

• BREAKING CAPACITY 250V ac– HBC HIGH BREAKING

CAPACITY 1500A– LBC LOW BREAKING

CAPACITY 35A or 10In– EBC ENHANCED BREAKING

CAPACITY 150A

• FUSING FACTORS– 1.7 OF FUSE RATING

– UL 248 Specification• 3 BASIC GATES

– HOLD 110% 4 HOURS *

(UL198G)– OPEN 135% 1 HOUR– OPEN 200% 2 MINUTES

• INTERRUPTING RATING– 125V 10kA – 250V 35A to 1500A

• FUSING FACTORS– 1.2/1.3 OF FUSE RATING

– MITI Specification• 3 BASIC GATES

– HOLD 130% 60 MINUTES

– OPEN 160% 60 MINUTES

– OPEN 200% 2 MINUTES

• INTERRUPTING RATING– 125V 500A– 250V 100A

• FUSING FACTORS– 1.5 OF FUSE RATING



Section 2Section 2 WIA Fuse Characteristics and Device Physics

– Basic Fuse Characteristics • Electrical Characteristics

– TC Curve– I2t– Fast Acting and Slo Blo Fuses

• Maximum Ratings (Breaking Capacity)– Fuse Voltage Rating– Pulse Withstanding Curve

• Thermal Characteristics– De-rating

– Fuse Construction and How it Affects Fuse Characteristics• Fuse Construction• Fuse Physics and Equations• Fuse I2t and Arcing• Fuse Element: Slow-blow vs. Fast Acting• Fuse Body Strength and Breaking Capacity


WIA Fuse Characteristics and Device Physics

Basic Fuse Electrical Characteristics

– TC Curve• Defines the fuse opening time• Illustrates phase change of the fuse element

state• Directly denotes the fuse rating• Difference in Slow Blow vs. Fast Acting • Typical overload 200% to 800% for

electronics fuse• Above 1000% considered to be short circuit

– I2t

1. Adiabatic Process: No heat transfer to surrounding. All energy concentrated in a specific area for a split second.

2. Measure of the energy required to open a fuse when

subjected to an adiabatic current pulse.

3. Due to adiabatic current pulses, the fusing element is

stressed both thermally and mechanically. Depending on

the energy and number of pulses it could weaken due to

aging:

- Fatigue

- Pre-diffusion

- Oxidation

0.01

0.1

1

10

100

1000

0.1 1 10 100 1000CURRENT IN AMPS

TIM

E I

N S

EC

ON

DS



– Fast Acting vs. Slo Blo Fuse Slo Blo:

Fast Acting:

t =2 Separation

t =4 Plasma expands, Burn Back continues

t =3 Arcing Starts and Burn Back of Element

Arc Extinguished Fuse Operated

t = 0 solid

t =1 liquid

solid & liquid

base=solid, pellet=liquid, mix=solid & liquid diffusion process on going

t = 0 base=solid, pellet=solid

t = 1 base=solid, pellet=liquid diffusion process starting

t =2 liquid alloy (base+pellet)

t =3 Separation

t =5 Plasma expands, Burn Back continues

Arc Extinguished Fuse Operated

t =4 Arcing Starts and Burn Back of Element



Maximum Ratings (Breaking Capacity) – Fuse Voltage Rating

The maximum system voltage for which the fuse can be used without affecting the breaking capacity.

When Fuse is subjected to high voltages

(>rated voltage) and high currents (> rated

breaking capacity), the fuse may explode.

Interrupt Rating = Breaking Capacity =

Prospective current a fuse can interrupt safely

at rated it’s voltage:

- No damage to environment

- Fuse remains intact

- Insulation resistance maintained

– Pulse Withstanding Capabilities

Ability of fuses to sustain a number of adiabatic current pulses containing a specified amount of energy with sufficient cooling in between.

- Pulse in % of I²t value

- Fuse remains intact with a minimum aging



Thermal Characteristics

– De-rating Curve and Fuse Re-rating

Temp. of Fusing Element = Ambient Temp. (TA ) + Temp. Increase caused by Current Flow (dT)

200

-800

° C

Fast Acting fuse

Slo-Blo fuse ( 232°C)Ta

dT

dT

tem

pera

ture

(° C

)

The influence of ambient temperature is for Slo Blo fuses much larger then for Fact Acting fuses.

+



– Fuse Elements normally consist of a conducting metallic strip or filament of varying geometries and materials depending upon the ampere rating and application

– Connective Material typically solder or conductive epoxy

– Body material selected to survive Breaking Capacity/Pulse Withstand ratings safely

– Filler can aid in achieving specific ratings while maintaining safe operation

– Specific Fast or Medium Acting fuse element designs

– Specific Slo-Blo or Time delay fuse element designs

Fuse Construction

Filler

Terminations (End Cap)

Connective Material

Element/Filament

Body

Connective Material

Terminations



Fuse Physics Equation

TC Curve EquationDefined as the difference between the heat generated and the heat lost to the surroundings by the fuse element is the remaining heat energy required to raise the temperature of the fuse element to its melting point. Written as:QI – QL = mCP ( (TE-TS)/Δt) ) = ρAXLCP ( (TE-TS)/Δt) ) where: QI = Heat Generated by Current = I²R CP = Specific Heat of conductorQL = Heat Lost to Surroundings Δt = Temperature change of conductorm = Mass of conductor L = Length of conductor

I 2T EquationJoule’s Law can be written as: Power (P) = I²R = mCPΔT / Δt where:m = Mass of conductorCP = Specific Heat of conductorΔT / Δt = Rate of Temperature change of conductor

Slo-Blo vs. Fast Acting EquationResistance is expressed as R = pL / A where:p = Resistivity of material (ohm-length)L = Length of materialA = Cross Sectional Area of material



Fuse I2t and Arcing



Fuse Elements: Slow-blow vs. Fast Acting

Non Diffusion (Fast Acting)

Diffusion (Slo-Blo)

Non Diffusion (Fast Acting)Diffusion (Slo-Blo)

At high overloads a Slo-Blo in principle acts like a Fast Acting fuse because no time is available to start the diffusion process. - High overloads: about 4In (4x current rating) and higher.

Diffusion starts at 150-170°C. Slo-Blo fuse elements should not be operated continuously above 150°C to prevent aging.

Although no Sn pellet / plating is present it is not recommended to load Fast acting fuses continuously above 175-225°C due to: - Oxidation of the fusing-element material - Change of material properties



Fuse Body Strength and Breaking Capacity

Interrupt Rating = Breaking capacityProspective current a fuse can interrupt safely at it’s rated voltage.

- No damage to it’s environment - Fuse body remains intact - Insulation resistance maintained (> 0.5MOhm)

Rated Voltage / Voltage Rating:- The maximum system voltage for which the fuse can be

used without affecting the breaking capacity- Typically 32, 63, 125, 250, 600V

- The rated voltage is marked on the fuse body or terminations

(end caps)

Breaking Capacity Factors

1. Air Pressure from out-gas (due to fuse opening) cannot be larger than fuse body can withstand

2. Temperature of fuse body due to fuse element melting and arcing must not be higher than the ignition temperature of the fuse body

3. Fuse arcing time (time to extinguish) must not be longer than fuse body can withstand (could cause ignition or even vaporize fuse body)

"Equivalent Fuse Body I2t"

as Breaking Capacity.



Section 3Section 3 WIA Fuse Telecom Applications Protection Examples

– Basic OV - OC Connection Topology • OV-OC Unit for Telecom Circuit Protection

– Circuit Protection Based on Telecom Applications Requirements• Customer Premises Equipment

– Transformer-Coupled Tip and Ring Circuits• High Speed Transmission Equipment & Interfaces

– ADSL– T1/E1 Protection– IDSN

• Analog Line Cards– SLIC Protection

• Data Line Protection– LAN/WAN Protectors

– Littelfuse Global Lab Capabilities• Qualification of Products• UL-Approved Customer Testing• Verification of Standards• Customer Application Testing


WIA Fuse Telecom Application Protection Examples

Basic OV - OC Connection Topology

• OC device (Fuse Open, PTC Trip)

• OV device to suppress transient

• OC device placed in front of OV devices (to help if OV device fails short)

Example: Basic OV – OC Protection



Customer Premises Equipment (CPE)CPE is defined as any telephone terminal or network equipment which resides at the customer's site and is connected to the Public Switched Telephone Network (PSTN)

Protection Requirements:CPE should be protected against overvoltages that can exceed 800V and against surge currents up to 100A. It should meet regulatory standards such as TIA -IS-968 and UL 60950

Example: Basic CPE (Phone, Modem) Protection Application



High Speed Transmission Equipment & InterfacesHigh speed transmission equipment encompasses a broad range of transmission protocols such as T1/E1, xDSL, and ISDN. Transmission equipment is located at the central office, customer premises, or remote locations.

Protection Requirements:High speed transmission equipment should be protected against overvoltages that can exceed 2500V and against surge currents up to 500A. It should meet regulatory standards such as TIA -IS-968, GR 1089-CORE, ITU K.20/K.21, and UL 60950

Example: T1/E1 Protection Application



Analog Line CardsAnalogy Line cards are highly susceptible to transient voltages that are deployed at the central office and in remote switching locations.

Protection Requirements:It is often necessary to protect Analogy line cards by on-hook (relay) and off-hook (SLIC) protection. It should meet regulatory standards such as TIA -IS-968, GR 1089-CORE, ITU K.20/K.21, and UL 60950

Example: SLIC Protection Application



Data Line ProtectionIn many office and industrial locations, data lines such as RS-232, Ethernet, and AC power lines run in close proximity to each other, which often results in voltage spikes being induced onto data lines, possibly causing damage to sensitive equipment.

Protection RequirementsData lines should be protected against overvoltages that can exceed 1500V and surge currents up to 50A.

Example: 10 Base-T Longitudinal Protection Application



Global Lab Capabilities• Qualification of all LF products• UL-Approved Customer Testing in ISO 17025 Lab (Des Plaines)

– High power (AC/DC up to 1KV/50KA) UL approvals available in DP– Telcordia approvals in DP planned (2008)

• Verification of Telcordia, ITU, IEC, FCC, and other industry, regulatory, and safety standards– Verification to various OC and OV standards

• Insure application meets standards before submitting for approval• Customer Application testing

– Assistance with design-in and performance verification• Help with selection of appropriate technology and rating

– Application troubleshooting• Assistance insuring proper OV/OC and primary/secondary protection coordination

– Competitive evaluations• Competitive or technology performance comparisons

– Reliability & Tin Whisker data/testing



Section 4Section 4 WIA Fuse Telecom Application Product Selection

– Typical WIA Fuse Types for Telecom and Related Design Features• Typical Axial Type Fuse (TR-5, Pico, 5x20, etc.)• Typical Surface Mount Type Fuse (Nano, Telecom Nano)

– Fuse Type/Series selection • Identify Fuse Dimensional Requirements• Identify Fuse Breaking Capacity Requirement

– Fuse rating selection• Identify Fuse Opening Time• Identify Fuse I2t Requirement• Identify Fuse De-rating Requirement


WIA Fuse Telecom Application Product Selection

Application Design Feature Required WIA fuse

Network Modems

Analog, xDSL, ISDN, T1

Must meet UL 1950 3rd Edition/UL 1549 and FCC 46 Part 68 specifications

Tele-Link (461 series)

2AG Slo-Blo Fuse (230 Series)

Desktop/PC-Card Modems

Must meet UL 1950 3rd Edition and FCC 46 Part 68 specifications


NANO Slo-Blo Fuse (452 Series)

Fax Machines/Business Machines

Must meet UL 1950 3rd Edition/UL 1549 and FCC 46 Part 68 specifications



Desktop Telephones Must meet UL 1950 3rd Edition/UL 1549 and FCC 46 Part 68 specifications



Answering Machines Must meet UL 1950 3rd Edition/UL 1549 and FCC 46 Part 68 specifications



Line Cards and PBXs Must meet UL 1950 3rd Edition/UL 1549 and FCC 46 Part 68 and Bellcore GR1089-Core specifications



Telecom/Internet Gateways

Must meet UL 1950 3rd Edition/UL 1458 and Bellcore GR1089-Core specifications



Typical WIA Fuse Types for Telecom Applications



Fuse Type/Series selection

Fuse Voltage Rating-The applied voltage fuse opens safely at (arcing occurs when fuse element melts, the voltage rating is the ability to suppress internal arcing)-Covered by NEC (National Electric Code) and UL-Standard voltage ratings: 32V, 63V, 125V, 250V, and 600VAC

Fuse Current Rating-Fuse is sensitive to changes in current-Fuse will melt after heated by over-current conditions-TC (Fuse melting time vs. current) curve

Typical Power Cross Requirement for Fuse-Meet 250V voltage rating for power cross-Meet 600V 40A (UL 60950)-Meet 600V 60A (GR 1089)

The TeleLink or 461 series -Rated at 250V-Meet 600V 40A or 600V 60A test



• Surge Rating Correlation to Fuse Rating

• Fuse Peak Pulse Current (Ipp)

– Ipp >= Ipk, Ipk=Vpk/Rtotal

– Longitudinal surges: Rtotal = Rtip + Rsource, Rsource=Vpk/Ipk

– Metallic surges: Rtotal = Rtip + Rring + Rsource, Rsource= Vpk/Ipk

Fuse Rating Selection



Section 5Section 5 Littelfuse WIA Product Road Map

– Wickmann Brand Fuse • TR/TE -5 Fuse Road Map

– Littelfuse Brand Fuse• Telecom Nano Fuse Road Map• 5x20 Fuse Road Map• 2AG, 3AG Fuse Road Map


PROJECTProducts Released in

2006Products Expected to be Released in 2007

Target Segment

350V Fast Acting Cartridge - 208 Series Ballasts, UPS

350V Slo Blo Cartridge - 209 Series Ballasts, UPS

Time Delay Pico - 472 Series Consumer Electronics

METI B 3AB - 388 Series White Goods - Japan Mkt

Various custom products ALL

3.6x10mm Platform SMPS

High Amp Nano - 20A - 30A Computer / Server

Enhanced Telelink Nano Telecom

Telecom Fuse Array Telecom

1206 Nano Consumer Electronics, SMPS

TE-5 100A Break Capacity SMPS

TR-5 150A Break Capacity SMPS

High I2t / HBC 215XA SMPS

5x20mm SMD Industrial

500V 6x32mm Fuse UPS

IEC Barrier Fuse Industrial

IEC Pico Fuse Industrial

DC Rated Cartridge Fuses UPS

TR-5 with 125C Operating Temperature SMPS



Physical value-added services for better overall efficiency

1. The complete package – Cartridge fuse with fuse-clip2. Cartridge fuse ( or Pigtail leaded too ) with Color coded / band3. Leaded fuses with kinking / lead forming4. Fuse ( Direct welded type ) with lead forming5. Fuse with heat-shrink tube6. Fuse pigtail leaded type with longer pigtail lead length (for instance 52mm)7. Taped and reeled/ammo-packed

1 2 3

4 5 6



Electrical value added services for specific/customized electrical applications and specifications

1. Enhanced breaking capacity / Short-circuit testing at ;• Higher voltages• Higher currents• VDC testing

2 Higher i2t request

3 Addition of or in accordance with • PSE • IEC/UL

4. Increased of rated voltage of fuse• 32v-rated to 125v-rated or even 250v-rated• 125v-rated to 250v-rated• 250v-rated to 350v-rated or any rated voltage needed

5. Tighter tolerance of parameters• Resistance, length, i2t, etc



Section 6Section 6 Telecom WIA Fuse Technology Challenges

– Fuse TC curve definition and tolerance control

– Higher Breaking Capacity/smaller package

– Multiple elements in one package

– Indication for open fuse

– Fuse reset feature

– Fuse technology combined with other technologies in one package

– Improved de-rating characteristics

– Higher operating temperatures


1 Confidential and Proprietary to Littelfuse, Inc. © 2005 Littelfuse, Inc. All rights reserved....

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Transcript of 1 Confidential and Proprietary to Littelfuse, Inc. © 2005 Littelfuse, Inc. All rights reserved....