PICO 304 Series - Littelfuse/media/electronics/product_presentation… · end-product may be used...
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PICO® 304 Series277V Encapsulated Fuse for Hazardous Locations Equipment
New Product IntroductionApril 2017
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What are hazardous locations?§ Combustible gases, vapors, and airborne dusts tend, by their very nature, to be
explosive when present in the right concentrations along with sources of sparks or excess heat. Over the years, these hazards have led to some catastrophic losses of life and property. In response to this hazardous potential, regulatory bodies around the world have worked to establish and refine codes & standards that will minimize the hazards associated with electrical equipment for use in these environments.
§ Areas are “classified” into groups based on the nature of explosive atmosphere present and the risk level of an explosion occurring
– “Hazardous (Classified) Locations” in North America– ”Explosive Atmospheres” in Rest of World
§ Due to safety risks associated with these areas, equipment used in these areas must be designed for explosion protection and must be third-party certified.
§ Electrical protection is based on two-key principles:Ø Energy limitation - To limit the spark energyØ Temperature limitation - To limit the surface temperature
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Examples of Explosive AtmospheresEnergy: Oil, Gas, Mines Food: Grain, Sugar, Brewing
Material Processing: Chemical, Tank Farm
Others: Pharmaceutical, Cosmetics, Pumping Station
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Definitions of Explosive AtmospheresWhat type of substance is
present?
Gases/Vapors(Class I)
Dust (Class II) Fibers/Flyings(Class III)
How often is the substance present?
On a normal basis –continuously or for long periods
Only in abnormal conditions
Division 1 Division 2
Divisions vs. Zones
Only in abnormal conditions
What type of substance is
present?
Gases/Vapors Dust
How often is the substance present?
Continuously or for long periods
Intermittently
Zone 0
Zone 20
Zone 1
Zone 21Zone 2
Zone 22
Gas:
Dust:
North America Rest of World
Harmonization now allows Zones in N. America!
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Intrinsic Safety Basics§ Protection principle based on energy limitation
– Fuses may be used as “infallible components” and are very instrumental in providing power limitation
– Power limitation is needed to prevent thermal conditions that could ignite explosive atmospheres
– Current rating (In) of fuse is used in all circuit analysis calculations!(1.7 safety factor is multiplied onto In)
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Basic Fuse Requirements from I.S. Standards§ For fuses relied upon to protect other components, 1.7x the nominal current rating is
expected to flow continuously– This “current limit” is used in all circuit analysis calculations for downstream circuits!– This current limit sets the required power ratings for other “infallible components” downstream (e.g., resistors, zener
diodes, thyristors, optical isolators, etc.)§ The minimum cold resistance of a fuse at the lowest operating ambient temperature of the
end-product may be used as a “resistor” to lower available current for thermal ignition (power) calculations
– Typically not a value shown on fuse manufacturers’ datasheets!– Designers usually have to test 10 samples to determine this value (per the standards)– Littelfuse hazardous location fuses have this data available (certificates, datasheets)
§ Fuses connected to non-intrinsically safe circuits typically require 1500A breaking capacity at 250VAC r.m.s.
– Non-intrinsically safe circuits are any circuit that is not energy-limited by “infallible components” as defined by the standards
– Typically assumed to have faults derived from AC mains supply (250VAC globally)§ If the fuse carries current while in an explosive atmosphere, it must be encapsulated!§ Spacing between fuse terminals must meet stricter requirements in I.S. standards
– At 250V rms (< 375V peak): 10.0 mm creepage distance in air, 3.3 mm under coating, or 2.0 mm under encapsulation
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Encapsulating Fuses§ Fuses protect other components, but what protects the
fuses?– When fuses open-circuit, arcing occurs within
the fuse– This arcing could have enough energy to ignite
the explosive atmosphere– Fuses must be encapsulated to prevent the
explosive atmosphere from entering the fuses
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PICO® 304 Series Surface Mount Fuse§ Product Overview
– The PICO® 304 Series offers a range of encapsulated fuses ideal for applications requiring up to 277V AC/DC in the oil and gas, mining and chemical andpharmaceutical industries
– Specially designed for intrinsic safety equipment– Its encapsulated design prevents heat and sparks
from being exposed to potentially explosive gases or dust in the environment
– The first SMD fuse certified to global intrinsic safety standards
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304 Series Features and Benefits
Features
§ Encapsulated and sealed design (1mm minimum), ideal for operation in a range of hazardous environments
§ Surface mount device§ High breaking capacity of 1500A @
277V AC/DC and current ratings ranging from 50mA to 750mA
§ Certified to UL 913, IECEx, ATEX and other standards for use in hazardous and potentially explosive atmospheres
Benefits
§ Eliminates the need for encapsulation (potting) or coating, which saves assembly time and money, reducing total end-product cost
§ Suitable for pick-and-place PCB assembly
§ Ideal for interfaces between intrinsically safe and non-intrinsically safe circuits
§ Speeds up the certification process for end-products
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304 Series Applications
Applications:
§ Testing, measuring or processing electronic and electrical equipment§ Motor controllers§ Communication handsets, two-way radios, and accessories (chargers,
docks, and so on)§ Process control and automation equipment§ Sensors§ Lighting§ Flow/gas meters
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Intrinsic Safety Barriers –Separating Intrinsically Safe & Non-intrinsically Safe Circuits
Intrinsic safety systems using galvanic isolator
§ Fuses are used as “infallible” current limiters for overvoltage protectors like zenerdiodes, diodes, TVS diodes, etc.
§ The current rating of the fuse is used to ensure two-thirds derating of other “infallible” components
– Per the intrinsic safety standards, a fuse is assumed to continuously carry 170% of its nominal current rating during fault conditions
§ Fuses also provide power limitation to downstream circuits under fault conditions
IS Circuits Non-IS Circuits
Required Zener diode power rating:
𝑃" =(1.7𝐼))(𝑉" + 𝑡𝑜𝑙. )
2 3⁄
Pz – Continuous power rating of Zener diodeIn – Nominal current rating of fuseVz – Nominal zenerbreakdown voltagetol. – Tolerance on zenerbreakdown voltage
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Application Example Galvanically isolated switch-mode power supply
§ Fuses protect galvanically separating components:– Set current limit for transformer windings, ultimately limiting fault temperature of windings– Set current limit for input/output of optical isolators, keeping fault power within isolators’ ratings
§ Set current limit for zener diodes, ultimately setting required power rating for zener diodes
Non-IS Circuits
IS Circuits
AC mains fuse
MOV
Schottkydiode
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Application Example Active voltage-limiting power supply circuit
§ Fuses protect passive and semiconductor components:– Set power rating requirements for resistors– Set power limit for voltage references, transistors, SCRs, reverse polarity diodes, and other semiconductors
§ Regardless of the circuit topology, a fuse is needed at the input to protect the active voltage limiting network
§ Redundant networks are required based on fault analysis required by I.S. standards
Non-IS Circuits
IS Circuits
Silicon controlled rectifier (SCR)
Diode or Schottky
diode
Silicon controlled rectifier (SCR)
Diode or Schottky
diode
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Application Example Galvanically isolated communication circuits
§ Typical communication circuits:– RS-232– RS-485– CAN & CANopen– HART– UART
§ Fuses protect galvanically separating components:– Set current limit for input/output of optical isolators, keeping fault power within isolators’ ratings
§ Set current limit for zener diodes, ultimately setting required power rating for zenerdiodes
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Application ExampleBattery Charge Circuits in Mobile Devices
§ Battery charging for mobile devices is typically done in a safe area, but can be done in explosive atmospheres if so designed
– Charger accessories (docking stations, power adapters, etc.) don’t need encapsulated fuses unless they are used in an explosive atmosphere
– Fuses in charger accessories need a breaking capacity of 1500A at 250VAC r.m.s.
§ Battery charge circuitry within mobile devices need encapsulated fuses– Fuse needs 1500A breaking capacity if input voltage (Um) is not specified and charger is not I.S. certified– Fuse sets required power rating of triple blocking diodes (for protection against battery discharge to the outside world via charging
contacts)
+
Um(input voltage)
–
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Explosive Atmospheres End-Products
Data Loggers, Mobile Computing and Communication
Instrumentation and Process Automation
Gas Detection
Process Fluid/Gas Flow Measurement
Lamps and Light Systems
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Designers of Intrinsic Safety ProductsGermany
UK
USAItaly France
Denmark
Singapore
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Comparison of Fuse Options
§ Rated 250VAC rms§ 1500A breaking capacity§ Low current ratings (≤ 1 A)§ (Almost) 10mm creepage
distance between end caps§ Low-price option§ Large fuse!§ NO special Hazardous Locations
certifications
§ Rated 250VAC rms / VDC§ 4000A breaking capacity§ Low current ratings (≤ 250 mA)§ < 10mm creepage distance
between end caps (requires coating or encapsulation)
§ Higher price than 5x20mm fuse§ Smallest fuse!§ NO special Hazardous Locations
certifications
§ Rated 277V rms / VDC§ 1500A breaking capacity§ Low current ratings (≤ 750 mA)§ 10mm creepage distance between end
caps (no coating or potting needed)§ Higher price than 242 Series§ Small fuse!§ cURus, IECEx & ATEX certifications
for Hazardous Locations
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Comparison of 304 Series with Existing Intrinsically Safe Product Series from Littelfuse
Series No.242
Barrier 259 259 UL913 304* 305
Photo
Current 50mA to 250mA 62mA to 5A 62mA to 5A 50mA to 750mA 50mA to 750mA
Voltage 250VAC/DC 125VAC/DC 125VAC/DC 277VAC/DC 277VAC/DC
Interrupting Rating
4000A / 250VAC4000A / 250VDC
50A / 125VAC300A / 125VDC
50A / 125VAC300A / 125VDC
1500A / 277VAC1500A / 277VDC
1500A / 277VAC1500A / 277VDC
Size (mm) 8.4 x 3.02dia 13.0 x 8.0dia 13.0 x 8.0dia 13.7 x 6 x 6.1L x W x H
15.6 X 9.0 dia
Certifications: cURus (UL 913, CSA No. 157), IECEx and ATEX Certificates for use in hazardous and potentially explosive atmospheres
Competition: IS Fusion – provides encapsulation on suppliers’ fuses and only certified to IECEx and ATEX – no UL913 or CSA No. 157
Markets and Apps: Safety Barriers, Gas Meters, Handhelds, Lamps, Oil, Gas, and Process Industries
Hazloc Fuses – 259-UL913, 304, 305 Series:Certifications:
cURus (UL 248-14)
Competition: Only Eaton/Cooper Buss. C308F Series
Markets and Apps: Safety Barriers, Gas Meters, Handhelds, Lamps, Oil, Gas, and Process Industries
Barrier Fuse – 242 Series:
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304 Series Electrical Specifications
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§ Dimensions (mm)
§ Marking
§ Part Numbering System
304
SERIES
AMP CODE.050 / .080 / .100 / .160 / .200 / .250 / .500 / .750
Quantity CodeZ = 800 pcsH = 100 pcs
Packaging CodeR = Tape and Reel
. 050 Z R
Dimensions, Marking and Part Numbering System
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Pricing, Samples, Availability and Contacts§ Pricing and Samples
- Please contact Littelfuse product management and sales representatives for pricing and samples availability.
§ Production Availability- Production lead-time: 4 weeks- Packaging: 1 week
§ Contacts Product Manager: Eva Jelezova [email protected] Product Manager: Allan Joseph Reano [email protected] Engineer: Sharie Lyn Mantilla [email protected] Marketing: Tim Patel, P.E. [email protected]
23Confidential and Proprietary to Littelfuse. Littelfuse, Inc. © 2017PROTECT | CONTROL | SENSE 23Confidential and Proprietary to Littelfuse. Littelfuse, Inc. © 2017PROTECT | CONTROL | SENSE
Sales Tools, Technical Support and Keywords§ Current datasheets are available on http://www.littelfuse.com/.
- Enter “304” in the search box
§ Application and Technical Support: 1-800-999-9445
§ Suggested Keywords§ 304 or 0304§ Encapsulated fuse§ Barrier fuse§ Intrinsically Safe§ Intrinsic Safety§ IS or I.S.
§ Hazardous Locations§ Explosive
atmospheres§ HazLoc§ Associated apparatus§ ATEX fuse
§ IECEx fuse§ UL 913 § 60079-11§ CSA C22.2 No. 157§ 1500A breaking
capacity