5SFP 125-R Equivalent & Substitute Parts

Part Overview

The 5SFP 125-R is a 125 mA, 250 V AC/DC fast-blow glass cartridge fuse with a 5mm x 20mm axial package manufactured by Bel Fuse Inc. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing system maintenance and new design implementations. Substitute parts must maintain identical electrical ratings, mechanical compatibility, and approval certifications to ensure reliable circuit protection without design modification.

Substiute Parts

5SFP 125-R

Bel Fuse Inc.In Stock: 10605SFP 125-R Datasheet

Current PartRFQ

BK/S500-V-125-R

Eaton - Electronics DivisionIn Stock: 914BK/S500-V-125-R Datasheet

DirectRFQ

0217.125MXEP

Littelfuse Inc.In Stock: 10610217.125MXEP Datasheet

SimilarRFQ

0235.125MXEP

Littelfuse Inc.In Stock: 8510235.125MXEP Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 5SFP 125-R are qualified based on strict electrical and mechanical parameter matching:

Primary Substitution Criteria:

• Current Rating: 125 mA (exact match required)
• Voltage Rating: 250 V AC (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Response Time: Fast Blow (exact match required)
• Package: 5mm x 20mm axial configuration (exact match required)
• Mounting: Through Hole (exact match required)
• Breaking Capacity: 35 A @ rated voltage (exact match required)

All three substitute parts meet these mandatory criteria. Secondary parameters including melting I²t, DC cold resistance, and dimensional tolerances vary within acceptable engineering ranges for this component category but do not affect functional substitution capability.

Parameter Comparison

Engineering Selection Recommendations

BK/S500-V-125-R (Eaton - Electronics Division) is the primary direct substitute. This part maintains all critical electrical and mechanical parameters with active product status and RoHS compliance. The melting I²t value of 0.005 is lower than the original 0.009, indicating slightly faster thermal response characteristics within the fast-blow category. DC cold resistance of 2.8 Ohms is lower than the original, reducing resistive heating in circuit applications.

0217.125MXEP (Littelfuse Inc., Series 217) provides an alternative substitute with active status and comprehensive approval certifications including CCC, CE, CSA, K-MARK, SEMKO, UL, and VDE. Operating temperature range matches the original specification. Melting I²t of 0.00478 and DC cold resistance of 3.82 Ohms fall between the original and Eaton specifications.

0235.125MXEP (Littelfuse Inc., Series 235) is a secondary substitute option with active status and CE, CSA, KC, and UL certifications. This part exhibits the highest DC cold resistance at 5.75 Ohms and the lowest melting I²t at 0.00273, indicating the fastest thermal response among all options. Operating temperature range matches the original specification.

All three substitute parts are electrically and mechanically compatible with the 5SFP 125-R. Selection should be based on availability, approval certifications required for the target application, and thermal response characteristics appropriate to the circuit protection requirements.

Frequently Asked Questions (FAQ)

Q: Can BK/S500-V-125-R replace 5SFP 125-R in existing designs? A: Yes. Both parts share identical current rating (125 mA), voltage rating (250 V AC), fuse type (cartridge glass), response time (fast blow), package (5mm x 20mm axial), and breaking capacity (35 A). Through-hole mounting is identical. The parts are electrically and mechanically interchangeable.

Q: What is the difference between the Littelfuse 0217.125MXEP and 0235.125MXEP options? A: Both are Littelfuse 125 mA, 250 V fast-blow glass cartridge fuses in 5mm x 20mm packages. The primary difference is thermal response: the 0235.125MXEP has a lower melting I²t (0.00273 vs 0.00478) and higher DC cold resistance (5.75 vs 3.82 Ohms), resulting in faster thermal response. Certification coverage differs slightly, with 0217.125MXEP offering broader approvals including K-MARK and SEMKO.

Q: Are dimensional variations between substitute parts significant? A: Dimensional variations are minor. The original 5SFP 125-R measures 0.217" diameter x 0.827" length. Littelfuse parts measure 0.236" diameter x 0.886" length, and Eaton measures 0.218" diameter x 0.831" length. These variations remain within standard mechanical tolerances for 5mm x 20mm axial cartridge fuses and do not affect PCB footprint compatibility or through-hole mounting.

Q: Which substitute part should be selected for new designs? A: Selection depends on application-specific requirements. For general-purpose replacement with broad certification coverage, 0217.125MXEP is recommended. For applications requiring faster thermal response, 0235.125MXEP is appropriate. For lowest resistive heating in low-impedance circuits, BK/S500-V-125-R is optimal. All three parts are active products with current manufacturing support.

Q: Do all substitute parts meet RoHS requirements? A: Yes. BK/S500-V-125-R is RoHS compliant. Both Littelfuse parts (0217.125MXEP and 0235.125MXEP) are ROHS3 compliant, meeting the most current RoHS directive requirements.