KLSR Series - UL Class RK1 Dual Element Time-Delay Fuse

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KLSR series RK1 fuses were the earliest type of current-limiting fuse developed. Their single-element, silver link design enables them to provide fast-acting overload and short-circuit protection. When used to protect inductive loads such as motors, solenoids, and transformers, KLSR series fuses must be greatly oversized to prevent opening the fuses on harmless inrush currents. In such applications, KLSR series fuses may only provide short-circuit protection.

We recommend using POWR-PRO™ LLNRK/LLSRK series RK1, dual-element, time-delay fuses in all new applications requiring the current-limiting ability of UL Class RK1 fuses, or in existing applications where fast-acting RK1 or RK5 fuses have been opening on harmless system surges such as motor starting currents.

  • Resistance heaters
  • Lighting circuits
  • Non-inductive loads
  • Molded case circuit breaker load centers and panelboards have increased interrupting ratings when “series rated” with Littelfuse KLNR/KLSR Class RK1 fuses. Refer to panelboard manufacturer’s literature for UL Listed combination of fuses and panelboards. Series ratings up to 200,000 amperes are available.
  • 200,000 A.I.R. — Reliable interruption of all overcurrents up to 200,000 amperes.
  • Extremely current limiting — Stops damaging short-circuit current faster than any mechanical protective device.
  • Fast-acting — Provides fast-acting protection to equipment such as variable speed drives, rectifiers and other equipment containing surge-sensitive components.
Longer Equipment Life:
  • Current-limiting design reduces damage to equipment caused by heating and magnetic effects of short-circuit currents.
  • Extremely current-limiting — often permits use of readily available, less costly equipment.
  • Used as input or output fuses for surge-sensitive components, such as variable speed drives and rectifiers, fast acting KLNR/KLSR fuses may prevent opening of expensive semiconductor fuses protecting individual components.
Easy to Use:
  • 200,000 A.I.R. rating minimizes need for short circuit calculations.
  • Refer to FLNR for KLNR dimensions and FLSR for KLSR dimensions.

Access specifications, certifications, check availability and order parts below

Catalog #Amps (A)VAC (V)VDC (V)Interrupting RatingOpeningSizeStockSamplesCompare
KLSR0011600250200 kA @ 600 VacFast-Acting (F)Industrial CartridgeCheckOrder
KLSR002260025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR003360025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR004460025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR005560025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR006660025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR008860025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0101060025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0121260025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0151560025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0202060025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0252560025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0303060025020 kA @ 250 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0353560030020 kA @ 300 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0404060030020 kA @ 300 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0454560030020 kA @ 300 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0505060030020 kA @ 300 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0606060030020 kA @ 300 VdcFast-Acting (F)Industrial CartridgeCheckOrder
KLSR0707060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR0808060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR0909060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR10010060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR11011060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR12512560030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR15015060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR17517560030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR20020060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR22522560030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR25025060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR30030060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR35035060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR40040060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR45045060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR50050060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder
KLSR60060060030020 kA @ 300 VdcFast-Acting (F)Knife-BladeCheckOrder

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