3SBP 2.5-R Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The 3SBP 2.5-R is a 2.5 A, 250 V AC/DC glass cartridge fuse manufactured by Bel Fuse Inc. in the 3AB/3AG form factor with slow-blow response characteristics. This part is classified as obsolete. Equivalent substitute parts from Littelfuse Inc. are available in active product status, offering direct functional replacement with maintained electrical and mechanical specifications.

Key Parameters

Parameter	Value
Current Rating	2.5 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (Axial)
Response Time	Slow Blow
Mounting Type	Through Hole
Operating Temperature Range	-55°C ~ 125°C

Substitute Part Grouping Explanation

Substitution eligibility is determined by matching the following critical parameters:

Current Rating: 2.5 A (exact match required)
Voltage Rating: 250 V AC (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (Axial) (exact match required)
Response Time: Slow Blow (exact match required)
Mounting Type: Through Hole (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

All five Littelfuse substitute parts (031502.5HXP, 031502.5MRT1BP, 031502.5MXP, 031502.5MXSLP, 031502.5VXP) meet these criteria and are direct functional equivalents. Differences in packaging format (Bulk vs. Tape & Reel) and regulatory certifications do not affect electrical or mechanical compatibility.

Parameter Comparison

Parameter	3SBP 2.5-R (Bel Fuse)	031502.5HXP (Littelfuse)	031502.5MRT1BP (Littelfuse)	031502.5MXP (Littelfuse)	031502.5MXSLP (Littelfuse)	031502.5VXP (Littelfuse)
Current Rating (Amps)	2.5 A	2.5 A	2.5 A	2.5 A	2.5 A	2.5 A
Voltage Rating - AC	250 V	250 V	250 V	250 V	250 V	250 V
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
Response Time	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (Axial)	3AB, 3AG, 1/4" x 1-1/4" (Axial)	3AB, 3AG, 1/4" x 1-1/4" (Axial)	3AB, 3AG, 1/4" x 1-1/4" (Axial)	3AB, 3AG, 1/4" x 1-1/4" (Axial)	3AB, 3AG, 1/4" x 1-1/4" (Axial)
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Size / Dimension	0.272" Dia x 1.280" L (6.90mm x 32.50mm)	0.275" Dia x 1.275" L (6.99mm x 32.39mm)	0.275" Dia x 1.275" L (6.99mm x 32.39mm)	0.275" Dia x 1.275" L (6.99mm x 32.39mm)	0.275" Dia x 1.275" L (6.99mm x 32.39mm)	0.275" Dia x 1.275" L (6.99mm x 32.39mm)
DC Cold Resistance	0.08 Ohms	0.0811 Ohms	0.0811 Ohms	0.0811 Ohms	0.0811 Ohms	0.0811 Ohms
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected
Product Status	Obsolete	Active	Active	Active	Active	Active

Engineering Selection Recommendations

All five Littelfuse substitute parts provide direct functional equivalence to the 3SBP 2.5-R. Selection between substitute options is based on packaging and certification requirements:

031502.5HXP, 031502.5MXP, 031502.5MXSLP, 031502.5VXP are supplied in Bulk packaging and are suitable for applications requiring standard component procurement. These parts maintain active product status with full regulatory compliance.

031502.5MRT1BP is supplied in Tape & Reel (TR) format and is appropriate for automated assembly processes and high-volume manufacturing environments.

Regulatory certifications vary across substitute options. The 3SBP 2.5-R carries CE, CSA, cULus, and PSE approvals. Littelfuse substitutes carry overlapping certifications (CE, CSA, UL, PSE, K-MARK, KC, METI) with variations by part number. Confirm certification alignment with application requirements before final selection.

Frequently Asked Questions (FAQ)

Q: Can Littelfuse 315 series fuses directly replace the obsolete Bel Fuse 3SBP 2.5-R?

A: Yes. All five Littelfuse substitute parts (031502.5HXP, 031502.5MRT1BP, 031502.5MXP, 031502.5MXSLP, 031502.5VXP) are direct functional equivalents. They match the critical electrical parameters (2.5 A, 250 V AC), fuse type (Cartridge, Glass), response time (Slow Blow), and mechanical form factor (3AB/3AG, 1/4" x 1-1/4" Axial).

Q: What is the difference between Bulk and Tape & Reel packaging options?

A: Bulk packaging (031502.5HXP, 031502.5MXP, 031502.5MXSLP, 031502.5VXP) is standard for manual assembly and component stocking. Tape & Reel packaging (031502.5MRT1BP) is formatted for automated pick-and-place assembly equipment and is typical in high-volume manufacturing. Electrical and mechanical specifications are identical.

Q: Are there dimensional differences between the original and substitute parts?

A: Minor dimensional variations exist within tolerance. The 3SBP 2.5-R measures 0.272" Dia x 1.280" L (6.90mm x 32.50mm), while Littelfuse substitutes measure 0.275" Dia x 1.275" L (6.99mm x 32.39mm). These differences are within standard mechanical tolerances for 3AB/3AG form factor fuses and do not affect fit or function in standard fuse holders.

Q: Do all substitute parts have the same regulatory certifications?

A: Regulatory certifications vary by Littelfuse part number. Common certifications include CE, CSA, and UL. Additional certifications include K-MARK, PSE, KC, and METI depending on the specific part. Verify that the selected substitute meets all certifications required by your application and regional standards.

Q: What is the difference in melting I²t between the original and substitutes?

A: The 3SBP 2.5-R has a melting I²t of 94, while all Littelfuse substitutes have a melting I²t of 130. Both values are within the slow-blow fuse classification and maintain the same response time characteristics for circuit protection.

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