Best R-Rated Motor Fuse Manufacturers (2026)

How this list was put together

We looked for manufacturers whose own websites or catalogs publish medium-voltage fuses with an R rating for motor and motor-controller protection, 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. We found five with a published R-rated range, and added ABB as a clearly labeled IEC alternative because many plants run IEC-built motor switchgear alongside North American starters.

Every R-rated fuse is a back-up fuse by class, so none is a stand-alone overload device. Entries describe the voltages, barrel counts and mountings each maker 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: Motor and soft-starter fuse replacements where a 30-day lead time and direct engineering contact matter

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 R-rated family covers medium-voltage motor and soft-starter fuses in single, double and triple barrel construction.

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.

DENCO does not publish R-rated equivalences to other brands. If you are replacing a fuse in an existing starter, send the part number from the fuse barrel and the starter nameplate details, and DENCO engineering will confirm whether a suitable DENCO part exists. DENCO also serves OEM and specialty custom design customers.

• R-rated motor and soft-starter fuses
• Single, double and triple barrel construction
• 30-day lead time on all products
• In-house factory lab testing; IPH Berlin third-party testing on request
• Direct line to engineering: 1-800-305-FUSE (3873)

See the DENCO range

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

Best for: Sites running Eaton AMPGARD medium-voltage motor starters

Eaton's Bussmann series catalog lists ANSI/IEEE R-rated medium voltage fuses in several constructions, including ACLS fuses listed for AMPGARD motor starters, BCLS bolt-in fuses and CLS ferrule fuses. Published part listings run through 2.4 kV and 4.8 kV ratings in single and double barrel versions, with larger bolt-in styles also listed.

If your starters are Eaton AMPGARD units, starting from Eaton's listing for that starter is the simplest path, because the starter maker generally specifies the R-rated fuse it was designed around.

• ACLS (AMPGARD), BCLS bolt-in and CLS ferrule styles
• Part listings at 2.4 kV and 4.8 kV
• Single and double barrel versions listed

Eaton (Bussmann series) website

3. Mersen, R-rated back-up medium voltage fuses

Best for: Buyers who need ferrule, bolt-on or DIN-dimension R-rated fuses, including 9F60 EJ-2 types

Mersen publishes R-rated back-up medium voltage fuses in three mounting families: ferrule mount at 2.5, 5 and 7.2 kV; bolt-on mount at 5, 7.2 and 15.5 kV; and DIN mount at 3.3, 5.5 and 7.2 kV. Its catalog lists Amp-Trap R-rated series alongside 9F60 EJ-2 series fuses, in 3-inch and 4-inch barrel diameters with ferrules for spring-reinforced clips.

Mersen's catalog also states that R-rated fuses must be coordinated with overload relays in combination motor starters, and that the motor starter manufacturer generally specifies the R-rated fuse size. The DIN-mount range is useful where North American R-rated behavior is needed in IEC-dimension equipment.

• Ferrule 2.5 to 7.2 kV; bolt-on to 15.5 kV; DIN mount 3.3 to 7.2 kV
• Catalog series: Amp-Trap R-rated and 9F60 EJ-2
• Hookeye bolt-in versions listed in the catalog

Mersen website

4. Littelfuse, Rosemont, Illinois

Best for: Motor circuits in hazardous locations that need a hermetically sealed R-rated option

Littelfuse, headquartered in Rosemont, Illinois, publishes an R-Rated Series for short-circuit protection of medium voltage motors, motor controllers and associated circuitry. Its curve library covers 2.75 kV, 5.5 kV and 8.25 kV fuses, with R numbers up to 24R or 36R depending on voltage.

The page lists a hermetically sealed version for hazardous locations, a bolt-in configuration with a hookeye option, and live parts and clips for single, double and triple barrel fuses. It also explains the division of duty clearly: the controller's overload relays handle overload and locked-rotor protection, and the fuse handles the short circuits beyond the controller's capability.

• Curves published for 2.75, 5.5 and 8.25 kV
• Hermetically sealed and bolt-in hookeye options
• Clips for single, double and triple barrel fuses

Littelfuse website

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

Best for: Motor circuits built on British or DIN-dimension fuse bases that still need R-rated back-up fuses

SIBA's HHM series are current-limiting back-up fuses for motor circuits, offered in British (HHBM-BM and HHBM-BR) and DIN (HHD-BM and HHD-BR) formats. SIBA's HHM catalog describes voltage ranges of 3.6 kV, 7.2 kV and 12 kV, and lists IEEE C37.40, C37.41 and C37.46 among the standards for the range alongside IEC 60282-1 and BS 2692-1.

SIBA says the range was developed to handle the cyclic loads typical of motor circuits with lower power losses. Its North American business is based in West Caldwell, New Jersey.

• HHM series: British and DIN formats, BR variants
• 3.6, 7.2 and 12 kV voltage ranges
• Catalog lists IEEE C37.46 and IEC 60282-1

SIBA website

6. ABB, CMF motor-circuit fuse-links

Best for: IEC-built motor switchgear where the fuse is specified to IEC 60644 rather than by an R number

ABB's CMF fuse-links are motor-circuit fuses designed around IEC 60644, the IEC specification for high-voltage fuse-links for motor circuit applications. They are not R-rated, so they are not a like-for-like substitute for an R-rated fuse in a North American starter.

ABB's medium-voltage fuse technical guide explains CMF selection from the motor's starting current, starting time (charts for 6, 15 and 60 seconds) and number of starts per hour. That method is worth knowing even if your plant uses R-rated fuses, because it shows which motor data a supplier needs to confirm a fuse.

• Specified to IEC 60644, not R-rated
• Selection by starting current, starting time and starts per hour
• Published technical guide with selection method

ABB (IEC alternative, not R-rated) website

What the R rating means

ANSI/IEEE C37.46 defines the R rating by one melting point: an R-rated fuse melts in 15 to 35 seconds at a current of 100 times the R number. A 2R fuse, for example, melts in that window at 200 A. The R number is not an ampere rating, which is why manufacturers list a separate continuous current for each R number.

R-rated fuses are back-up fuses by class. Below their minimum interrupting current they cannot be relied on to clear, so the starter's overload relay and contactor must deal with overloads and low-level faults before the fuse is asked to act.

How to choose a manufacturer

These checks apply whichever supplier you choose:

• Start from the fuse the starter manufacturer specifies, and the part number on the existing fuse.
• Match voltage, R number, barrel count (single, double or triple) and mounting (ferrule clips or bolt-in).
• Confirm that the starter's overload relay and contactor coordinate with the fuse's minimum interrupting current.
• Check whether you need an indicator or striker, or a sealed fuse for a hazardous location.
• For soft starters, give the supplier the starter model and motor data, not only the motor size.
• Weigh lead time against the spares you hold; DENCO quotes 30 days on all products.

Frequently asked questions