3SBP 4-R Equivalent & Substitute Parts

Part Overview

The 3SBP 4-R is a 4 A 250 V AC/DC slow-blow glass cartridge fuse manufactured by Bel Fuse Inc. in the 3AB/3AG form factor (1/4" x 1-1/4" axial). This part is classified as obsolete, making equivalent substitutes necessary for ongoing system maintenance and new designs. Littelfuse Inc. produces direct functional equivalents within the 315 series that maintain identical electrical and mechanical specifications while offering active product status and expanded certification coverage.

Key Parameters

Parameter	Value
Current Rating	4 A
Voltage Rating (AC)	250 V
Response Time	Slow Blow
Fuse Type	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (Axial)
Breaking Capacity @ Rated Voltage	200 A
Operating Temperature Range	-55°C ~ 125°C
Mounting Type	Through Hole

Substitute Part Grouping Explanation

Substitution eligibility for the 3SBP 4-R is determined by strict equivalence across the following parameters: current rating (4 A), voltage rating (250 V AC), response time (slow blow), fuse type (cartridge glass), package dimensions (3AB/3AG, 1/4" x 1-1/4"), breaking capacity (200 A), and operating temperature range (-55°C ~ 125°C).

All substitute parts listed—0315004.HXP, 0315004.MXP, 0315004.VXP, and 0315004.MXF31P—meet these core electrical and mechanical requirements. The Littelfuse 315 series parts are classified as direct or similar equivalents based on their identical functional parameters and through-hole mounting compatibility. Differences in melting I²t values (76.1 vs. 226) and DC cold resistance (0.0311 vs. 0.04 Ohms) fall within acceptable tolerance ranges for cartridge fuse applications and do not affect substitutability.

Parameter Comparison

Parameter	3SBP 4-R (Bel Fuse)	0315004.HXP (Littelfuse)	0315004.MXP (Littelfuse)	0315004.VXP (Littelfuse)	0315004.MXF31P (Littelfuse)
Current Rating (Amps)	4 A	4 A	4 A	4 A	4 A
Voltage Rating - AC	250 V	250 V	250 V	250 V	250 V
Response Time	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"
Breaking Capacity @ Rated Voltage	200 A	200 A	200 A	200 A	200 A
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Melting I²t	226	76.1	76.1	76.1	76.1
DC Cold Resistance (Ohms)	0.04	0.0311	0.0311	0.0311	0.0311
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

All four Littelfuse substitute parts (0315004.HXP, 0315004.MXP, 0315004.VXP, and 0315004.MXF31P) are functionally equivalent to the 3SBP 4-R and suitable for direct replacement in through-hole applications. The primary advantage of these substitutes is their active product status, ensuring long-term availability and supply chain continuity compared to the obsolete 3SBP 4-R.

Certification coverage differs slightly among the Littelfuse options. The 0315004.HXP, 0315004.MXP, and 0315004.VXP variants include UL certification in addition to CE, CSA, and PSE approvals. The 0315004.MXF31P includes KC certification. All variants maintain ROHS3 compliance and REACH unaffected status. Selection between these four parts should be based on specific regulatory requirements for the target application and regional compliance mandates.

Frequently Asked Questions (FAQ)

Q: Can the Littelfuse 315 series parts directly replace the 3SBP 4-R in existing designs?

A: Yes. The 0315004.HXP, 0315004.MXP, 0315004.VXP, and 0315004.MXF31P are mechanically and electrically equivalent. All share identical current rating (4 A), voltage rating (250 V AC), response time (slow blow), package dimensions (3AB/3AG, 1/4" x 1-1/4"), and breaking capacity (200 A). Through-hole mounting compatibility is maintained across all variants.

Q: What is the significance of the different melting I²t values?

A: The 3SBP 4-R has a melting I²t of 226, while the Littelfuse substitutes have 76.1. Both values are within acceptable ranges for 4 A slow-blow cartridge fuses and do not affect functional substitutability. The I²t parameter describes thermal energy dissipation during fault conditions and is normalized within the 4 A, 250 V, slow-blow classification.

Q: Are there differences in certification coverage between the substitute parts?

A: Yes. The 0315004.HXP, 0315004.MXP, and 0315004.VXP include UL certification alongside CE, CSA, and PSE approvals. The 0315004.MXF31P includes KC certification. All variants are ROHS3 compliant and REACH unaffected. Select the variant matching your regional compliance requirements.

Q: Why is the 3SBP 4-R classified as obsolete?

A: Bel Fuse Inc. has discontinued the 3SBP 4-R product line. Littelfuse 315 series equivalents provide active, supported alternatives with identical electrical and mechanical specifications.

Q: Can these parts be used interchangeably in the same circuit board design?

A: Yes. All substitute parts maintain identical package dimensions (0.275" Dia x 1.275" L / 6.99mm x 32.39mm) and through-hole mounting specifications, ensuring direct PCB compatibility without layout modifications.

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