Mersen LJD Back-Up R-Rated Med...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$3,938.54
Mersen LJD Back-Up R-Rated Medium Voltage Fuse, Ferrule Mount, 5080V

Mersen LJD Back-Up R-Rated Medium Voltage Fuse, Ferrule Mount, 5080V

(No reviews yet) Write a Review

Model: 9F60LJD506

In Stock (leaves warehouse same day if ordered before 3pm ET)

$3,938.54
Adding to cart… The item has been added
Free Shipping on orders over $199
We price match and offer bulk discounts! Click Add to Quote. It's quick and easy.
✨
Earn points with this purchase! You can redeem points for giftcards, iPads, XBox's and more. View Rewards
Free Keying on all locks
You may also like

Mersen LJD Back-Up R-Rated Medium Voltage Fuse, Ferrule Mount, 5080V

The Mersen LJD Back-Up R-Rated Medium Voltage Fuse is a current-limiting, high interrupting rating fuse engineered for the short-circuit protection of medium voltage motors and motor controllers. Rated at 5080V AC (UL) with a 50 kA AC maximum interrupting rating (I1), this R-Rated back-up fuse is designed to be coordinated with overload relays in combination motor starters, with exact fuse sizing typically specified by the motor starter manufacturer. It is available with 3-inch (size D) or 4-inch (size E) diameter barrels fitted with ferrule terminals, mounted in spring-reinforced clips for a secure connection.

Key Features

  • Ferrule Connection: Silver-plated copper ferrule terminals seat in spring-reinforced clips for a secure, low-resistance connection.
  • High Interrupting Rating: 50 kA AC maximum interrupting rating (I1) delivers robust short-circuit protection for demanding medium voltage circuits.
  • R-Rated Back-Up Protection: Speed/characteristic is R-Rated (Design Details: 6R), intended as a back-up fuse coordinated with overload relays in combination motor starters.
  • Medium Voltage Rating: Rated voltage of 5080V AC (UL), suited for medium voltage motor and motor controller circuits.
  • Dual Frequency Operation: Rated for 50/60 Hz AC applications.
  • Visual Indication: Built-in visual indicator system provides at-a-glance blown-fuse status.
  • Durable Body: Epoxy body/insulating material provides mechanical strength and dielectric protection.
  • Flexible Barrel Sizing: Offered in 3-inch (size D) or 4-inch (size E) diameter barrels to match application requirements.

Technical Specifications

  • Indication System: Yes
  • AC or DC: AC
  • Design Details: 6R
  • Connection/Terminal Type: Ferrule
  • Connection/Terminal Material: Silver-Plated Copper
  • Mounting: Clip
  • AC Max I.R./Breaking Capacity (I1): 50 kA
  • Frequency: 50/60 Hz
  • Rated Voltage AC (UL): 5080 V
  • Body/Insulating Material: Epoxy
  • Packaging: 1 EA

Typical Applications

  • Medium Voltage Motor Short-Circuit Protection
  • Combination Motor Starters Coordinated with Overload Relays
  • Industrial Motor Control Centers
  • Medium Voltage Switchgear and Motor Control Equipment

Why Mersen?

Mersen builds the LJD Back-Up R-Rated Fuse with silver-plated copper ferrule terminals, spring-reinforced clip mounting, and a durable epoxy body, backed by a 50 kA interrupting rating and integrated visual indication. That combination gives electrical professionals a dependable, code-coordinated component for short-circuit protection in demanding medium voltage motor and motor controller applications.

Manufacturer Resources

Mersen Product Catalog

Product Specs

list_batch:
MERSEN-20260825
Product Type:
Fuse
Connection Type:
Ferrule
Voltage Rating:
5080V
Product Material:
Epoxy
Configuration:
Clip Mount
Department:
Electrical
Product Group:
Circuit Protection
Product Subgroup:
Fuses

Mersen 9F60LJD506 – Frequently Asked Questions

1) What is an R-rated back-up fuse like the Mersen LJD actually used for?
The Mersen LJD is a current-limiting medium voltage fuse built for short-circuit protection of medium voltage motors and motor controllers, not for overload protection. It works as the back-up element in a combination motor starter, where an overload relay handles running overloads and the fuse clears short circuits. That split is why the fuse size is normally dictated by the motor starter manufacturer rather than chosen off a load calculation.
2) Will the Mersen 9F60LJD506 fuse work on a 4160V motor circuit?
Yes. The LJD fuse carries a 5080V AC (UL) rated voltage, so it covers nominal medium voltage motor circuits up to that figure, including 2400V and 4160V systems. It is an AC-only device rated for 50/60 Hz. Do not apply it on DC.
3) Is a 50 kA interrupting rating enough for my medium voltage motor control center?
The LJD is rated 50 kA AC maximum interrupting (I1), which has to equal or exceed the available fault current at the point of installation. Compare it against the short-circuit study value for that bus. Because the fuse is current-limiting, it also reduces the let-through energy reaching the starter and contactor downstream.
4) How does the Mersen LJD fuse mount, and do I need clips?
Ferrule terminals, silver-plated copper, seating into spring-reinforced fuse clips. It is a clip-mount fuse, so the holder or starter cubicle must already have matching clips sized for the barrel. There is no bolt-on stud or blade option here.
5) Can I substitute a Class CC or midget fuse for a medium voltage R-rated fuse?
No. The LJD is a 5080V AC medium voltage fuse, and low voltage fuses are not interchangeable with it at any point. Products such as the Littelfuse CCMR Series Class CC time-delay fuse or the Littelfuse BLF Series midget fast-acting fuse rated 250V belong on low voltage branch circuits and control power, not in a medium voltage motor starter.
6) Can a Littelfuse CCMR040 Class CC time-delay fuse be used in place of the Mersen 9F60LJD506 R-rated fuse?
No. The Mersen 9F60LJD506 LJD is a medium voltage fuse rated 5080V AC with a 50 kA AC interrupting rating, built as an R-rated back-up fuse coordinated with the overload relay in a combination motor starter. The Littelfuse CCMR040 is a Class CC time-delay fuse in the CCMR series rated 40A - a low voltage branch-circuit and motor-circuit fuse. The two are different voltage classes and different mounting styles; the LJD seats on ferrule terminals in spring-reinforced clips in medium voltage motor control equipment, so a Class CC fuse and its rejection-style holder will not substitute.
7) I need a fuse for a medium voltage motor starter - would a Littelfuse AGU or AGA glass fuse work instead?
No. The Littelfuse AGU and the AGA5 are glass tube fuses in the AGU and AGA series, used in low voltage electronic and automotive-style circuits. Medium voltage motor and motor controller short-circuit protection calls for an R-rated back-up fuse like the Mersen 9F60LJD506 LJD, rated 5080V AC at 50 kA, with sizing normally specified by the motor starter manufacturer so it coordinates with the overload relay.
8) What is the difference between the size D and size E LJD barrels?
The LJD is built with either a 3-inch (size D) or 4-inch (size E) diameter barrel. The barrel size has to match the clip spacing and cubicle space of the starter or holder it goes into, so order to what the equipment is prepped for rather than by preference.
9) What does the 6R design detail on the Mersen LJD mean?
6R is the R-rating of the fuse, the code used for medium voltage motor back-up fuses. R-rated fuses are selected by the starter manufacturer's coordination table against the motor and overload relay, not by a straight ampere rating the way a general-purpose fuse is.
10) Does the Mersen 9F60LJD506 come as a single fuse or a three-pack?
Packaging is 1 EA, so each order quantity is one fuse. A three-phase starter needs three, and on a fuse operation most specifications call for replacing all three rather than just the one that cleared.
11) Is the Littelfuse BLF midget fuse an equivalent to the Mersen LJD ferrule fuse because both are cylindrical?
They share a cylindrical shape only. The Littelfuse BLF is a midget fast-acting fuse rated 250V with a laminated tube body. The Mersen LJD 9F60LJD506 is rated 5080V AC, uses an epoxy body with silver-plated copper ferrule terminals, carries a 50 kA AC interrupting rating, and comes in 3-inch (size D) or 4-inch (size E) diameter barrels. For medium voltage motor short-circuit protection, the LJD is the correct part and a 250V midget fuse is not an alternative.
12) What is the difference between the Mersen 9F60LJD506 and a Square D PowerLogic energy meter fuse pack?
They do different jobs. The Square D PowerLogic fuse pack is a set of three 0.5A 600V fuses for metering circuits. The Mersen 9F60LJD506 LJD is a current-limiting R-rated back-up fuse rated 5080V AC with a 50 kA AC interrupting rating, clip-mounted on ferrule terminals, intended for short-circuit protection of medium voltage motors and controllers in motor control centers and switchgear. A metering fuse pack protects instrument wiring, not the motor branch.
13) Can I tell if a Mersen LJD fuse has blown without pulling it out?
Yes. The LJD has a built-in visual indicator, so blown status can be read at a glance during a cubicle inspection instead of removing and testing the fuse.
14) Will the epoxy body of the LJD fuse hold up in an industrial switchgear cubicle?
The body is epoxy, chosen for mechanical strength and dielectric strength at medium voltage. It is the standard construction for fuses going into motor control centers and medium voltage switchgear.
How fast can I get the Mersen 9F60LJD506 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Mersen 9F60LJD506 come with a warranty?
Absolutely. The Mersen 9F60LJD506 is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Mersen 9F60LJD506?
You can call, text, or email our expert support team for fast answers. We’re here to help with product selection, installation tips, and troubleshooting. Contact Us
Why buy the Mersen 9F60LJD506 from ZenSupply?
ZenSupply makes it easy to get the commercial door hardware you need—fast shipping, expert support, and rewards on every order. Our team is always ready to help you choose the right product for your project.
!