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Littelfuse FLQ Series 500V/300VDC Slo-Blo Time-Delay Midget Fuse
The Littelfuse FLQ Series is a family of Slo-Blo (Time-Delay) fuses built in the compact Midget/5AG package for supplemental protection in control and motor circuits. Rated 500VAC and 300VDC with a 10000A@500VAC interrupting rating, the FLQ Series is available in ampere ratings from 1A to 9A -- including 1A, 1.25A, 1.6A, 2A, 3A, 5A, and 9A -- to match a wide range of circuit loads. UL and CSA 500 volt ratings allow the FLQ Series to be applied on 480 volt circuits, making it a dependable choice for control power transformers, solenoids, and small motor supplemental protection.
Key Features
- Ampere Rating Range: Available from 1A to 9A (1A, 1.25A, 1.6A, 2A, 3A, 5A, 9A) for precise supplemental protection across varying circuit loads.
- Voltage Rating: 500VAC / 300VDC construction supports a wide range of control circuit applications.
- Time-Delay Operation: Slo-Blo/Time Lag (T)/Time Delay opening characteristic rides through high inrush currents without nuisance operation.
- Interrupting Rating: 10000A@500VAC for safe clearing of high fault currents.
- Package Size: Midget/5AG form factor fits standard midget fuse holders and blocks.
- UL and CSA 500 Volt Ratings: Permit use on 480 volt circuits for added application flexibility.
- Supplemental Motor Protection: Provides supplemental protection to small motors alongside dedicated branch-circuit protection.
- Control Circuit Protection: Protects control power transformers, solenoids, and circuits with high inrush currents.
Certifications & Compliance
- UL 500 Volt Rating
- CSA 500 Volt Rating
- Suitable for Use on 480 Volt Circuits
Technical Specifications
- Series: FLQ
- VAC (V): 500
- VDC (V): 300
- Ampere Rating Options (A): 1, 1.25, 1.6, 2, 3, 5, 9
- Opening: Slo-Blo/Time Lag (T)/Time Delay
- Interrupting Rating: 10000A@500VAC
- Package Size: Midget/5AG
Typical Applications
- Small Motor Supplemental Protection
- Control Power Transformer Circuits
- Solenoid Circuits
- High Inrush Current Circuits
- 480V/500V Industrial Control Panels
Why Littelfuse?
Littelfuse backs the FLQ Series with UL and CSA 500 volt ratings, a 10000A@500VAC interrupting rating, and a time-delay design purpose-built to withstand inrush without nuisance opening. With ampere ratings spanning 1A to 9A, engineers and electricians can specify the exact FLQ Series fuse needed for motors, control power transformers, and solenoid circuits, all in a compact Midget/5AG package delivering dependable, code-compliant performance.
Manufacturer Resources
Spec Sheet
Product Specs
- Series:
- FLQ
- Product Type:
- Time-Delay Fuse
- Voltage Rating:
- 500VAC/300VDC
- Amperage Rating:
- 1A-9A
- Standards:
- UL-CSA
- Department:
- Electrical
- Product Group:
- Circuit Protection
- Product Subgroup:
- Fuses
Littelfuse FLQ001 – Frequently Asked Questions
1) Will a Littelfuse FLQ fuse fit a standard midget fuse holder?
Yes. The FLQ Series is built in the Midget/5AG package, so it drops into standard midget fuse holders and blocks used in industrial control panels.
2) Can I use the FLQ fuse on a 480V control circuit?
Yes. The FLQ carries UL and CSA 500 volt ratings, which is what permits its use on 480 volt circuits. It is rated 500VAC and 300VDC, with a 10000A interrupting rating at 500VAC.
3) Which amp ratings does the Littelfuse FLQ come in, and what are the part numbers?
Orderable ratings run 1A through 9A: 1A (FLQ001), 1.25A (FLQ1.25), 1.6A (FLQ01.6), 2A (FLQ002), 3A (FLQ003), 5A (FLQ005) and 9A (FLQ009). Pick the rating by the circuit load you are protecting, not by the holder size, since all of them share the same Midget/5AG body.
4) My control transformer fuse keeps blowing on startup. Will a time-delay midget fuse fix that?
That is exactly what the FLQ is built for. It is a Slo-Blo / Time Lag (T) fuse, so it rides through the inrush of a control power transformer, solenoid or small motor without nuisance opening, then still clears a real fault. A fast-acting fuse of the same amp rating will keep opening on the magnetizing surge.
5) Can I use an FLQ fuse as the branch-circuit protection for a motor?
No. The FLQ provides supplemental protection to small motors and is meant to sit alongside dedicated branch-circuit protection, not replace it. For branch-circuit motor duty you want a current-limiting class fuse such as a Mersen A2D-R Class RK1 time-delay fuse.
6) What is the difference between the Littelfuse FLQ midget fuse and a Mersen A2D-R Class RK1 time-delay fuse?
Both are time-delay fuses, but they are built for different parts of the system. The Littelfuse FLQ is a Slo-Blo time-delay fuse in the compact Midget/5AG package rated 500VAC/300VDC, intended for supplemental protection of control power transformers, solenoids and small motors, with ampere ratings from 1A to 9A. The Mersen A2D-R is a Class RK1 time-delay fuse with SmartSpot blown-fuse indication, and the A2D-20R version is rated 250VAC/250VDC. Class RK1 fuses mount in standard Class R clips and are branch-circuit rated, while the midget FLQ fits midget fuse holders and blocks. If the drawing calls for a Class R fuse block, the FLQ will not fit it.
7) I need a time-delay fuse above 9A for a motor circuit - what should I use instead of the FLQ?
The Littelfuse FLQ Series covers 1A through 9A only, so a larger motor load needs a different fuse. The Mersen A2D400R is a Class RK1 time-delay fuse rated 400A with SmartSpot indication, sized for branch-circuit motor protection rather than the supplemental role the FLQ fills. Confirm your holder is a Class R block before ordering, since Class RK1 bodies do not fit midget clips.
8) Can the FLQ be used on a DC circuit?
Yes, up to 300VDC. The FLQ is rated 500VAC / 300VDC, so on DC control or drive circuits the 300V figure is the one to design to.
9) Do I need a 500V fuse or will a 250V midget fuse do for my panel?
Fuse voltage rating must be equal to or greater than the circuit voltage, so a 250V midget cannot be used on a 480V circuit. The FLQ's 500VAC UL/CSA rating is what qualifies it there. On a 120V or 240V control circuit a 500V fuse is still acceptable, since a higher voltage rating is never a problem.
10) Is the Littelfuse FLQ UL listed for use in industrial control panels?
The FLQ carries UL and CSA 500 volt ratings. That is the basis for applying it on 480 volt circuits and in 480V/500V industrial control panels.
11) Can I use a Mersen D0R0 Amp-Trap fuse in place of a Littelfuse FLQ?
No. The Mersen A055F1D0R0-150E is a D0R0 Series Amp-Trap E-rated medium voltage fuse with a ferrule terminal, used on medium voltage transformer and feeder circuits. The Littelfuse FLQ is a low voltage Slo-Blo midget fuse rated 500VAC/300VDC for control and small motor circuits. They are not interchangeable in either direction.
12) Is the Square D EMFP3 energy meter fuse pack a substitute for a 1A Littelfuse FLQ?
Not as a general replacement. The Square D PowerLogic EMFP3 is a set of three 0.5A 600V fuses supplied for PowerLogic energy meter voltage inputs. The Littelfuse FLQ starts at 1A and is rated 500VAC/300VDC in the Midget/5AG package for control power transformers, solenoids and small motor supplemental protection. Use the EMFP3 where a PowerLogic meter calls for it, and the FLQ where a midget holder and a 1A to 9A time-delay characteristic are specified.
13) My panel has a 250V control circuit - do I need the FLQ or is a lower voltage fuse acceptable?
The Littelfuse FLQ is rated 500VAC/300VDC, and a fuse may always be applied at or below its voltage rating, so it works on a 250V control circuit and also carries the UL and CSA 500 volt ratings that allow use on 480 volt circuits. If you want blown-fuse indication on a 250V circuit and have Class R clips, the Mersen A2D-20R is a Class RK1 time-delay fuse rated 250VAC/250VDC with SmartSpot indication - but it cannot be moved up to a 480V circuit.
14) I need a small fuse for a metering circuit, not a motor. Is the FLQ the right pick?
The FLQ's smallest rating is 1A, which may be coarser than a meter circuit needs. For instrument and energy meter duty the Square D PowerLogic Energy Meter Fuse Pack is a set of three 0.5A 600V fuses made for that purpose.
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Does the Littelfuse FLQ001 come with a warranty?
Absolutely. The Littelfuse FLQ001 is backed by a manufacturer’s warranty.
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