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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
Confidential and Proprietary to Littelfuse, Inc. © 2005 Littelfuse, Inc. All rights reserved.
1
Telecom WIA Training
Section 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
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2
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 I 2t
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.
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3
Fuse Definition and Telecom Circuit Protection
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.
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4
Fuse Definition and Telecom Circuit Protection
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.
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5
Fuse Definition and Telecom Circuit Protection
Telecom System Test Standards
Subscriber
Premises
Central Office
Outside Plant
MDF
Customer
Premise
Equipment
(CPE)
Network
Street
Interface Cabinet &
Device SLIC (if on
(NID) DLC system)
YD/T993
ITU-T K.21
FCC P 68
UL 60950
YD/T993
ITU-T K.21
FCC P 68
UL 60950
UL 497
YD/T1082
ITU-T K.45
GR 1089
UL 60950
UL 497
SLIC
Switch
DDF
To
PSTN
Trunk Line (T1,
T3, HDSL, etc.)
Overhead
Cable
Underground
Cable
YD/T 694 or
YD/T 940
ITU-T K.28
GR 1089
UL 60950
UL 497
YD/T950
ITU-T K.20
GR 1089
UL 60950
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Fuse Definition and Telecom Circuit Protection
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
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Telecom WIA Training
Section 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
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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
–
1. Adiabatic Process: No heat transfer to surrounding. All
I2t
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
1000
100
TIME IN SECONDS
•
•
10
1
0.1
0.01
0.1
1
10
100 1000
CURRENT IN AMPS
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9
WIA Fuse Characteristics and Device Physics
–
Fast Acting vs. Slo Blo Fuse
Slo Blo:
t = 0 base=solid,
pellet=solid
Fast Acting:
t = 0 solid
t = 1 base=solid, pellet=liquid
diffusion process starting
solid & liquid
t =2 Separation
t =2 liquid alloy
(base+pellet)
base=solid, pellet=liquid, mix=solid &
liquid diffusion process on going
t =1 liquid
t =3 Arcing Starts and
Burn Back of Element
t =4 Plasma expands,
Burn Back continues
t =3
Separation
t =4 Arcing Starts and
Burn Back of Element
t =5 Plasma expands,
Burn Back continues
Arc Extinguished Fuse
Operated
Arc Extinguished Fuse
Operated
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WIA Fuse Characteristics and Device Physics
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
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11
WIA Fuse Characteristics and Device Physics
Thermal Characteristics
– De-rating Curve and Fuse Re-rating
+ (dT)
Temp. of Fusing Element = Ambient Temp. (TA ) + Temp. Increase caused by Current Flow
dT
Fast Acting
fuse
dT
Ta
Slo-Blo fuse
( 232°C)
The influence of ambient temperature is for Slo
Blo fuses much larger then for Fact Acting fuses.
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12
WIA Fuse Characteristics and Device Physics
Fuse Construction
Terminations (End Cap)
–
Connective Material
–
Element/Filament
Filler
Body
Connective Material
–
–
–
–
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
Terminations
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13
WIA Fuse Characteristics and Device Physics
Fuse Physics Equation
TC Curve Equation
Defined 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 conductor
QL = Heat Lost to Surroundings
Δt = Temperature change of conductor
m = Mass of conductor
L = Length of conductor
I 2T Equation
Joule’s Law can be written as:
Power (P) = I²R = mCPΔT / Δt where:
m = Mass of conductor
CP = Specific Heat of conductor
ΔT / Δt = Rate of Temperature change of conductor
Slo-Blo vs. Fast Acting Equation
Resistance is expressed as
R = pL / A where:
p = Resistivity of material (ohm-length)
L = Length of material
A = Cross Sectional Area of material
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14
WIA Fuse Characteristics and Device Physics
Fuse I2t and Arcing
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15
WIA Fuse Characteristics and Device Physics
Fuse Elements: Slow-blow vs. Fast Acting
Diffusion (Slo-Blo)
Non Diffusion (Fast Acting)
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.
Non Diffusion (Fast Acting)
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
Diffusion (Slo-Blo)
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WIA Fuse Characteristics and Device Physics
Fuse Body Strength and Breaking Capacity
Interrupt Rating = Breaking capacity
Prospective 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
"Equivalent Fuse Body I2t"
as Breaking Capacity.
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)
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17
Telecom WIA Training
Section 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
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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
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WIA Fuse Telecom Application Protection Examples
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
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WIA Fuse Telecom Application Protection Examples
High Speed Transmission Equipment & Interfaces
High 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
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WIA Fuse Telecom Application Protection Examples
Analog Line Cards
Analogy 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
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WIA Fuse Telecom Application Protection Examples
Data Line Protection
In 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 Requirements
Data lines should be protected against overvoltages that can exceed 1500V and surge currents up to 50A.
Example: 10 Base-T Longitudinal Protection Application
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WIA Fuse Telecom Application Protection Examples
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
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24
Telecom WIA Training
Section 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
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WIA Fuse Telecom Application Product Selection
Typical WIA Fuse Types for Telecom Applications
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
2AG Slo-Blo Fuse (230 Series)
NANO Slo-Blo Fuse (452 Series)
Fax Machines/Business
Machines
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 Telephones
Must meet UL 1950 3rd Edition/UL 1549
and FCC 46 Part 68 specifications
Tele-Link (461 series)
2AG Slo-Blo Fuse (230 Series)
Answering Machines
Must meet UL 1950 3rd Edition/UL 1549
and FCC 46 Part 68 specifications
Tele-Link (461 series)
2AG Slo-Blo Fuse (230 Series)
Line Cards and PBXs
Must meet UL 1950 3rd Edition/UL 1549
and FCC 46 Part 68 and Bellcore
GR1089-Core specifications
Tele-Link (461 series)
2AG Slo-Blo Fuse (230 Series)
Telecom/Internet
Gateways
Must meet UL 1950 3rd Edition/UL 1458
and Bellcore GR1089-Core specifications
Tele-Link (461 series)
2AG Slo-Blo Fuse (230 Series)
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WIA Fuse Telecom Application Product Selection
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
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WIA Fuse Telecom Application Product Selection
Fuse Rating Selection
•
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
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Telecom WIA Training
Section 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
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Telecom WIA Training
PROJECT
Products Released in
2006
Products 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
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30
Telecom WIA Training
1
2
3
4
5
6
Physical value-added services for better overall efficiency
1.
2.
3.
4.
5.
6.
7.
The complete package – Cartridge fuse with fuse-clip
Cartridge fuse ( or Pigtail leaded too ) with Color coded / band
Leaded fuses with kinking / lead forming
Fuse ( Direct welded type ) with lead forming
Fuse with heat-shrink tube
Fuse pigtail leaded type with longer pigtail lead length (for instance 52mm)
Taped and reeled/ammo-packed
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Telecom WIA Training
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
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Telecom WIA Training
Section 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
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33