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PICO® 304 Series277V Encapsulated Fuse for Hazardous Locations Equipment

New Product IntroductionApril 2017

2Confidential and Proprietary | Littelfuse, Inc. © 2017 2Confidential and Proprietary | Littelfuse, Inc. © 2017

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


Examples of Explosive AtmospheresEnergy: Oil, Gas, Mines Food: Grain, Sugar, Brewing

Material Processing: Chemical, Tank Farm

Others: Pharmaceutical, Cosmetics, Pumping Station


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!


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)


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


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


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


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


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


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


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


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


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


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)

–


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


Designers of Intrinsic Safety ProductsGermany

UK

USAItaly France

Denmark

Singapore


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


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:


304 Series Electrical Specifications


§ 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

22Confidential and Proprietary to Littelfuse. Littelfuse, Inc. © 2017PROTECT | CONTROL | SENSE 22Confidential and Proprietary to Littelfuse. Littelfuse, Inc. © 2017PROTECT | CONTROL | SENSE

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

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