GENERAL

This category covers power and distribution fuses with voltage ratings above 600 V.

These fuses are intended to provide overcurrent protection in accordance with ANSI/NFPA 70, "National Electrical Code," and are intended for installation in specific metal-enclosed switchgear.

These fuses are not intended to be interchanged with other manufacturers' fuses or with other classes of certified fuses. Each fuse is intended to only be replaced with a fuse of the same manufacturer, type and ratings. The melting times at specified overcurrents are shown by each manufacturer's published time-current curves, which may vary between manufacturers, and between fuse types and/or models.

Where used, the term "current-limiting" indicates a relationship between the cutoff (peak let-through) current to prospective available current, within the current-limiting range of the fuse, in accordance with characteristic curves published by the manufacturer. When operated within its current-limiting range, a current-limiting fuse introduces a high resistance to reduce current magnitude and duration, resulting in subsequent current interruption.

This category covers two major classes of fuses:

Power class fuses are generally used in three-phase applications, in substations, cabinets, or electrical vaults where a large amount of electrical power is being supplied to a distribution system. They are normally used where fault currents are high, X/R ratios are high, and/or severe transient recovery voltages (TRV) are anticipated.

Distribution class fuses are generally used in single-phase applications on a distribution line on single-phase taps or for protecting single-phase transformers. They are suitable for use in three-phase applications where the high capabilities of the power class fuse are not required.

Each of these classes is further subdivided into three types:

Back-up current-limiting fuses provide fault current interrupting duty only between their maximum interrupting rating and their minimum interrupting rating. They must be coordinated with other overcurrent protective device(s) which will interrupt below that level.

General purpose current-limiting fuses are not intended to interrupt currents below the current that causes melting of the fuse in not less than 1h. This current is their rated low current, which may be referred to as their rated minimum interrupting rating. They must be coordinated with other overcurrent protective device(s) which will interrupt below that level.

Full range current-limiting fuses are intended to interrupt any current between the minimum current that can cause melting of its elements (at the highest ambient specified by the manufacturer) and its maximum interrupting rating.

Specific devices covered under this category are as follows:

E-rated Fuses

Characteristics — E-rated fuses are current-limiting power fuses in the voltage range of 2.8 kV through 38 kV, intended for use on ac circuits only. E-rated fuses may have either full range or general-purpose characteristics, as designated in the individual certifications.

E-rated fuses have the following melting-time performance characteristics:

An E-rated fuses rated 100 A or less will melt in 300 seconds at an rms current within the range of 200 to 240% of its continuous current rating.

An E-rated fuse rated greater than 100 A will melt in 600 seconds at an rms current within the range of 220 to 264% of its continuous current rating.

The melting times at higher overcurrents are shown by each manufacturer's published time-current curves, which may vary between manufacturers and between fuse types and/or models.

Markings — Each fuse is marked with the manufacturer's name or trademark, manufacturer's type or identification number, rated continuous current, rated maximum voltage, rated frequency, rated maximum interrupting current, and "E" following the continuous current rating (e.g., 100E).

General Purpose Fuses

Characteristics — General purpose fuses are current-limiting power fuses in the voltage range of 2.8 kV through 38 kV, intended for use on ac circuits only. General purpose fuses have general purpose characteristics only.

Markings — Each fuse is marked with the manufacturer's name or trademark, manufacturer's type or identification number, rated continuous current, rated maximum voltage, rated frequency, rated maximum interrupting current, and rated low current.

Fuse Links

Characteristics — Type K and Type T distribution fuse links are for voltages up to 38 kV, intended for use on ac circuits only.

Markings — Each link is marked with the manufacturer's name or trademark and rated continuous current followed by the type identification (e.g., 40K).

The smallest shipping container is required to be marked with the manufacturer's name or trademark, the manufacturer's type or identification number, and rated continuous current, followed by the type identification.

PRODUCT IDENTITY

One of the following product identities appears on the product:

    E-rated Fuse

    Fuse Link

    General-purpose Fuse

ADDITIONAL INFORMATION

For additional information, see Electrical Equipment for Use in Ordinary Locations (AALZ).

REQUIREMENTS

The basic standards used to investigate products in this category are:

a. ANSI/IEEE C37.40 (1993), "IEEE Standard Service Conditions and Definitions for High-Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories"

b. IEEE C37.41 (2000), "IEEE Standard Design Tests for High-Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories"

In addition to the standards specified in items a and b above, the basic standard used to investigate general purpose current-limiting power fuses and E-rated fuses is ANSI C37.46 (2000), "American National Standard for High Voltage Expulsion and Current-Limiting Type Power Class Fuses and Fuse Disconnecting Switches."

In addition to the standards specified in items a and b above, the basic standard used to investigate fuse links is ANSI C37.42 (1996), "American National Standard Specification for High-Voltage Expulsion Type Distribution Class Fuses, Cutouts, Fuse Disconnecting Switches and Fuse Links."

All fuses covered under this category are intended to be applied as specified in ANSI/IEEE C37.48 (1997), "IEEE Guide for Application, Operation, and Maintenance of High-Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories".

UL MARK

The Certification Mark of UL on the product or on the smallest unit container in which the product is packaged is the only method provided by UL to identify products manufactured under its Certification and Follow-Up Service. The Certification Mark for these products includes the UL symbol, the words "CERTIFIED" and "SAFETY," the geographic identifier(s), and a file number.

Alternate UL Mark

The Listing Mark of UL on the product or on the smallest unit container in which the product is packaged is the only method provided by UL to identify products manufactured under its Listing and Follow-Up Service. The Listing Mark for these products includes the UL symbol (as illustrated in the Introduction of this Directory) together with the word "LISTED," a control number, and the product name "E-rated Fuse,""General Purpose Fuse" or "Fuse Link."

The Listing Mark is marked on the fuse for E-rated and general purpose fuses; the Listing Mark is marked on each package for fuse links, with or without the UL symbol on the fuse link.

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UL, in performing its functions in accordance with its objectives, does not assume or undertake to discharge any responsibility of the manufacturer or any other party. UL shall not incur any obligation or liability for any loss, expense or damages, including incidental or consequential damages, arising out of or in connection with the use, interpretation of, or reliance upon this Guide Information.