Littelfuse L50S Series Very Fa...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$105.31
Littelfuse L50S Series Very Fast-Acting Semiconductor Fuse, 500V

Littelfuse L50S Series Very Fast-Acting Semiconductor Fuse, 500V

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Model: L50S050

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

$105.31
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Littelfuse L50S Series Very Fast-Acting Semiconductor Fuse, 500V

The Littelfuse L50S Series High-Speed Semiconductor Fuse delivers supplementary protection for SCRs, diodes, thyristors, triacs, transistors, and other solid-state devices used in variable speed drives, power rectifiers, UPS systems, and DC power supplies. Engineered with Littelfuse-developed metallurgical, polymer, and materials technology, the L50S Series is rated 500VAC / 450VDC and is available in ampere ratings from 50A to 200A to match a wide range of solid-state protection needs. Each fuse in the series features a Very Fast-Acting (FF) opening characteristic for extremely current-limiting, no-time-delay interruption, and carries UL Recognition for supplementary protection in UL listed equipment.

Key Features

  • Ampere Rating Range: Available from 50A to 200A to size protection for varying semiconductor load requirements.
  • Voltage Rating: 500VAC / 450VDC for use across AC and DC solid-state equipment circuits.
  • Very Fast-Acting (FF) Opening: No time-delay, current-limiting operation protects sensitive semiconductor devices from damaging fault currents.
  • High Interrupting Capability: Interrupting ratings up to 20000A@450VDC deliver reliable interruption of overcurrents to meet demanding system requirements.
  • Extremely Current Limiting: Low I2t and peak let-through currents meet the requirements of most semiconductor devices.
  • UL Recognized: High-speed fuses may be used to provide supplementary protection in UL listed equipment.
  • Purpose-Built Design: Designed specifically for supplementary protection of solid-state semiconductor devices rather than general branch-circuit use.

Certifications & Compliance

  • UL Recognized

Technical Specifications

  • Refer to manufacturer documentation for complete technical specifications.

Typical Applications

  • Variable Speed Drives requiring fast semiconductor protection
  • Power Rectifiers and DC Power Supplies
  • UPS Systems and Standby Power Equipment
  • Protection of SCRs, Diodes, Thyristors, Triacs, and Transistors
  • Solid-State and Electronic Power Equipment

Why Littelfuse?

Littelfuse engineers apply advanced metallurgical, polymer, and materials research along with mathematical modeling and computerized statistical analysis to every fuse in the L50S Series. The result is consistent quality, accuracy, and predictable performance backed by UL Recognition, making the L50S Series a dependable choice for protecting critical semiconductor devices such as SCRs, diodes, thyristors, and triacs across variable speed drives, rectifiers, and UPS systems.

Product Specs

Listing:
UL Recognized
Product Type:
Semiconductor Fuse
Voltage Rating:
500VAC / 450VDC
Series:
L50S
Configuration:
Very Fast-Acting (FF)
Department:
Electrical
Product Group:
Circuit Protection
Product Subgroup:
Fuses

Littelfuse L50S050 – Frequently Asked Questions

1) Can a Littelfuse L50S fuse be used as the branch circuit protection for a drive panel?
No. The L50S Series is built for supplementary protection of solid-state devices (SCRs, diodes, thyristors, triacs, transistors), not general branch-circuit use. It carries UL Recognition for supplementary protection inside UL listed equipment, which means it sits in series with a separate branch-circuit protective device that handles the code-required overcurrent protection. Keep the L50S where it belongs: directly protecting the semiconductor stack.
2) Is a very fast-acting fuse the right choice, or should I use a time-delay fuse on my drive?
For semiconductor protection, very fast-acting is the right class. The L50S carries an FF (very fast-acting) characteristic with no time delay and extremely current-limiting behavior, which is what holds let-through I2t below what an SCR or diode can survive. A time-delay fuse rides through inrush and will not clear quickly enough to save the device. If you need inrush tolerance for a motor or transformer, that belongs on the branch-circuit fuse upstream, not in the semiconductor leg.
3) Can I substitute a standard branch-circuit fuse for a Littelfuse L50S?
No. The L50S Series is a semiconductor fuse with a Very Fast-Acting (FF) opening characteristic, designed for supplementary protection of SCRs, diodes, thyristors, triacs and transistors - its low I2t and peak let-through are what keep a solid-state device alive during a fault. A general-purpose or time-delay branch-circuit fuse of the same amp rating will let through far more energy and will not protect the semiconductor. If you need a different part, stay within the high-speed semiconductor family: the Bussmann KAW, FBP, KAX or SF100X1000HP Series are all semiconductor fuses, selected by matching voltage class and amp rating.
4) My drive has a 1000VDC bus - can I use a Littelfuse L50S fuse?
No. The Littelfuse L50S Series is rated 500VAC / 450VDC, so it is not suited to a 1000VDC bus. For that voltage class, look at the Bussmann KAX Series, which is a 1000VDC non-indicating semiconductor fuse, or the Bussmann SF100X1000HP Series. Both are semiconductor fuses intended for the same solid-state protection duty as the L50S but at the higher DC voltage rating. Keep the L50S for 500VAC / 450VDC drive, rectifier and UPS circuits.
5) Which amp ratings does the L50S series come in?
L50S covers 50A through 200A, and the orderable ratings are 50A (L50S050), 125A (L50S125), and 200A (L50S200). Size the fuse to the semiconductor's I2t and peak let-through withstand, not just to the load current, since the point of this fuse is to clear faster than the device can fail.
6) What other brands of semiconductor fuse could I use instead of the Littelfuse L50S?
Bussmann is the usual cross. The KAW Series and the FBP Series (a blade-end, non-indicating semiconductor fuse) are the comparable high-speed options to look at. For a higher-voltage DC bus the L50S cannot cover at its 450VDC limit, the Bussmann KAX Series is a 1000VDC non-indicating semiconductor fuse, and the SF100X1000HP Series is another high-performance option. Match voltage class, amp rating, and body/mounting style before substituting, since high-speed fuse bodies are not universally interchangeable.
7) Will a Littelfuse L50S protect my drive against an SCR short circuit?
That is what it is for. The L50S is extremely current limiting, with low I2t and low peak let-through, which is the mechanism that keeps a shorted SCR or diode fault from cascading through the rest of the bridge. Interrupting capability runs up to 20,000A at 450VDC. Compare the fuse's published let-through values against your device's I2t withstand rating to confirm coordination for your specific bridge.
8) What equipment do Littelfuse L50S fuses typically go into?
Variable speed drives, power rectifiers, DC power supplies, UPS and standby power equipment, and other solid-state power gear where SCRs, diodes, thyristors, triacs, or transistors need fault protection. For MRO stocking on a plant with 480V drives, the 50A, 125A, and 200A L50S ratings cover a broad slice of those feeds.
9) How do I identify the exact L50S part number to order?
The part number is the series plus the three-digit amp rating: L50S050 for 50A, L50S125 for 125A, L50S200 for 200A. All three are the 500VAC / 450VDC very fast-acting version of the series, so amperage is the only thing you specify.
How fast can I get the Littelfuse L50S050 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 Littelfuse L50S050 come with a warranty?
Absolutely. The Littelfuse L50S050 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 Littelfuse L50S050?
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 Littelfuse L50S050 from ZenSupply?
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