Best E-Rated Transformer Fuse Suppliers (2026)

How this list was put together

We looked for manufacturers whose own websites or catalogs publish fuses with an E rating for transformer, feeder or potential-transformer duty, and loaded each source in September 2026. Where a site blocked automated access, we recorded that and used only text from that manufacturer's own domain or its own published catalog.

An E rating is a melting characteristic defined by ANSI/IEEE C37.46, so the rating itself is comparable across makers. It does not fix voltage, interrupting rating, dimensions or mounting, so each entry describes the formats the supplier publishes. We did not test anyone's products and make no performance comparison. DENCO is first because this is DENCO's site; its entry gives buyer-fit reasons, not a claim that it outperforms the others.

1. DENCO Fuses, Miami, Florida

Best for: Replacing GE-pattern 9F60 fuses and buying E-rated, PT and other MV families from one supplier on a 30-day lead time

DENCO Fuses, Inc. was incorporated in Florida in 1988 as DenMar Transit Engineering (later DenMar Fuses). Its team has over 100 years of combined experience, solely in manufacturing electrical fuses. Its E-rated family is a current-limiting transformer protection range covering the 9F60/EJ-1, 9F62/EJO-1 and Clip Lock 14 series, supplied with or without a trip indicator or microswitch. For the primaries of potential transformers, DENCO also offers high-interrupting current-limiting ferrule PT fuses that are non-venting and carry a blown-fuse indicator.

DENCO's catalog publishes one direct E-rated equivalence: G.E. 9F60 Series to DENCO E-Rated Type EJ-1. For any other brand, send the part number and DENCO engineering will confirm whether a suitable DENCO part exists. DENCO quotes a 30-day lead time on all products; lead times across the industry are commonly longer. Fuses are manufactured in an ISO 9001:2015 certified facility, tested in-house at DENCO's factory lab, and can be sent for third-party testing at IPH Berlin (Germany) on client request.

Because DENCO also makes R-rated, C-rated, loadbreak elbow, dropout and oil-immersed transformer fuses, a utility, transit operator or electrical contractor can often cover a substation's medium-voltage fuse list with one engineering contact.

• E-rated series: 9F60/EJ-1, 9F62/EJO-1, Clip Lock 14
• Options: trip indicator or microswitch
• Published cross-reference: G.E. 9F60 Series to DENCO E-Rated Type EJ-1
• 30-day lead time on all products
• Direct line to engineering: 1-800-305-FUSE (3873)

See the DENCO range

2. Eaton, Bussmann series medium voltage E-rated fuses

Best for: Plants standardized on Bussmann series fuses that want per-voltage data sheets and remote open-fuse signaling

Eaton's Bussmann series catalog has a dedicated ANSI/IEEE E-rated medium voltage fuse range, with separate data sheets for 2.75 kV, 5.5 kV, 8.3 kV and 15.5 kV fuses and a 15.5 kV sheet describing feeder circuit, switchgear and transformer protection. It also publishes E-rated DIN-style fuses and a PT fuse data sheet for potential and small power transformers.

The product page lists indoor/outdoor ratings on select fuses, open-fuse indication with an available microswitch for remote indication, a striker option, and states that fuses are 100% X-ray inspected. Part listings include single, double and triple barrel constructions in ferrule and bolt-in styles.

• Data sheets for 2.75, 5.5, 8.3 and 15.5 kV E-rated fuses
• E-rated DIN and PT fuse ranges also published
• Microswitch and striker options listed

Eaton (Bussmann series) website

3. Mersen, E-rated general purpose medium voltage fuses

Best for: Buyers who want ferrule, bolt-on and clip-lock E-rated fuses from 2.75 kV up to 38 kV, plus published transformer sizing charts

Mersen's E-rated general purpose range is published in three mounting styles: ferrule mount from 2.75 kV through 38 kV, and bolt-on and clip-lock mounts from 5.5 kV through 15.5 kV. Its medium voltage catalog lists the Amp-Trap CS-3 series alongside 9F60 Type EJ-1, 9F60 Type EJO-1 and 9F62 Type EJO-1 fuses, and describes blown-fuse indicators and outdoor use for the 9F62 and 9F60 EJO types.

Mersen also publishes an application note with typical primary fuse sizing charts for three-phase transformers at common medium voltages. Those charts are a useful cross-check when you are reviewing an existing installation, though they do not replace the equipment maker's data or a coordination study.

• Ferrule 2.75 to 38 kV; bolt-on and clip-lock 5.5 to 15.5 kV
• Catalog series: Amp-Trap CS-3, 9F60 EJ-1/EJO-1, 9F62 EJO-1
• Transformer protection application note with sizing charts

Mersen website

4. Littelfuse, Rosemont, Illinois

Best for: Hazardous-location installations that need a hermetically sealed E-rated fuse option

Littelfuse, headquartered in Rosemont, Illinois, publishes an E-Rated Series of medium-voltage fuses for power transformers, potential transformers, power centers, feeder centers and unit substations. Its time-current curve library for the series runs from 2.75 kV up to 38 kV.

The page lists a hermetically sealed version for hazardous locations (an S suffix on the part number) and live parts and mounting clips for single, double and triple barrel fuses, sold in pairs.

• Published curves from 2.75 kV to 38 kV
• Hermetically sealed option for hazardous locations
• Clips for single, double and triple barrel fuses

Littelfuse website

5. SIBA, North American headquarters in West Caldwell, New Jersey

Best for: Sites mixing ANSI E-rated and IEC or DIN-style transformer fuses, including submersible applications

SIBA's North American business is based in West Caldwell, New Jersey. Its U.S. brochure describes high-voltage fuses from 2.4 kV to 40.5 kV and states that its medium and high voltage fuses are available with ANSI/IEEE, E-rated and IEC standards for transformer protection, including submersible applications.

The same brochure lists full-range, general purpose and back-up current-limiting classes, with striker pins of 80 N and 120 N. That mix suits facilities that run both North American and European-pattern switchgear.

• HV fuses from 2.4 kV to 40.5 kV
• ANSI/IEEE, E-rated and IEC transformer fuses
• Striker pins of 80 N and 120 N

SIBA website

6. S&C Electric, SM and SMD power fuses

Best for: Utility and industrial substations that specify E-rated solid-material power fuses rather than current-limiting fuses

S&C publishes SM and SML power fuses for indoor distribution from 4.16 kV through 34.5 kV, and SMD power fuses for outdoor distribution substations, both aimed at protecting transformers and cables. Its rating tables list E ratings (for example 200E and 400E fuse units), and the product pages offer several time-current speeds including Standard, Slow and Very Slow.

These are solid-material power fuses with silver or nickel-chrome fusible elements; S&C does not describe them as current-limiting fuses. Include them when you are comparing E-rated options for substation transformers, but keep in mind that the interrupting behavior differs from the current-limiting fuses above.

• SM/SML indoor: 4.16 kV through 34.5 kV
• SMD outdoor distribution substations
• E-rated fuse units in multiple speeds

S&C Electric Company website

What the E rating guarantees, and what it does not

ANSI/IEEE C37.46 defines the E rating by a single melting point. An E-rated fuse of 100 A or less must melt in 300 seconds at a current between 200% and 240% of its rating. Above 100 A, it must melt in 600 seconds at between 220% and 264% of its rating.

That point is what makes two makers' 65E fuses electrically comparable at that one test. The rest of the curve, the voltage rating, the interrupting rating, barrel count, clip centers and indicator all still need to match the original, which is why a fuse that physically fits is not automatically a correct replacement.

How to choose a supplier

For most transformer and PT replacements, the practical checks are the same whichever supplier you use:

• Match the existing part number, voltage class, E rating and mounting (ferrule, bolt-on or clip-lock).
• Confirm the interrupting rating is at least the available fault current at the fuse location.
• Decide whether you need a visual indicator, a striker or a microswitch for remote signaling.
• Check outdoor or enclosure requirements; not every E-rated fuse is rated for outdoor use.
• Ask for the time-current curves and compare them with the original, not just the rating letter.
• Weigh lead time against how many spares you hold; DENCO quotes 30 days on all products.

Frequently asked questions