3SBP 300 Equivalent & Substitute Parts

Part Overview

The 3SBP 300 is a 300 mA, 250 V AC/DC slow-blow glass cartridge fuse in 3AB/3AG package format (1/4" x 1-1/4" axial). Manufactured by Bel Fuse Inc., this component is classified as obsolete. Due to its obsolete status and limited ongoing availability, identifying equivalent substitute parts from active manufacturers is necessary for design continuity and procurement reliability.

Key Parameters

Parameter	Value
Current Rating	300 mA
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Response Time	Slow Blow
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (Axial)
Mounting Type	Through Hole
Breaking Capacity @ Rated Voltage	35 A
Operating Temperature Range	-55°C ~ 125°C

Substitute Part Grouping Explanation

Substitute parts for the 3SBP 300 are qualified based on the following electrical and mechanical parameters:

Current Rating: 300 mA (exact match required)
Voltage Rating (AC): 250 V (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Response Time: Slow Blow (exact match required)
Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (Axial) (exact match required)
Mounting Type: Through Hole (exact match required)
Breaking Capacity @ Rated Voltage: 35 A (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

All three substitute parts from Littelfuse Inc. (0315.300HXP, 0315.300MXP, 0315.300VXP) meet these criteria and are classified as active products with current manufacturing status.

Parameter Comparison

Parameter	3SBP 300 (Bel Fuse)	0315.300HXP (Littelfuse)	0315.300MXP (Littelfuse)	0315.300VXP (Littelfuse)
Current Rating (Amps)	300 mA	300 mA	300 mA	300 mA
Voltage Rating - AC	250 V	250 V	250 V	250 V
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
Response Time	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)
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Breaking Capacity @ Rated Voltage	35 A	35 A	35 A	35 A
Operating Temperature	-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)
DC Cold Resistance	3.8 Ohms	3.135 Ohms	3.135 Ohms	3.135 Ohms
Melting I²t	1.85	0.73	0.73	0.73
Approval Agency	CE, CSA, PSE, UL	CE, CSA, UL	CE, CSA, UL	CE, CSA, UL
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Obsolete	Active	Active	Active

Engineering Selection Recommendations

The three Littelfuse substitute parts (0315.300HXP, 0315.300MXP, 0315.300VXP) are direct functional equivalents to the obsolete 3SBP 300. All three parts satisfy the electrical and mechanical requirements for substitution.

Key advantages of the Littelfuse alternatives:

Active product status ensures ongoing availability and supply chain reliability
ROHS3 compliance meets current environmental regulations, whereas the 3SBP 300 is RoHS non-compliant
Dimensional tolerances are within acceptable limits for through-hole mounting applications
All three parts maintain CE, CSA, and UL certifications

Minor parameter variations exist in DC cold resistance (3.135 Ohms vs. 3.8 Ohms) and melting I²t (0.73 vs. 1.85). These differences remain within the functional envelope for 300 mA, 250 V slow-blow fuse applications. The Littelfuse parts exhibit faster thermal response characteristics due to lower melting I²t values, which is consistent with modern fuse design standards.

Frequently Asked Questions (FAQ)

Q: Are the Littelfuse 0315.300HXP, 0315.300MXP, and 0315.300VXP parts interchangeable with the 3SBP 300?

A: Yes. All three Littelfuse parts meet the electrical and mechanical specifications required for direct substitution. They share identical current ratings (300 mA), voltage ratings (250 V AC), fuse type (cartridge, glass), response time (slow blow), package format (3AB/3AG), and breaking capacity (35 A).

Q: What is the difference between the three Littelfuse substitute parts?

A: The 0315.300HXP, 0315.300MXP, and 0315.300VXP parts are functionally equivalent. All three are manufactured by Littelfuse Inc., carry active product status, and meet identical electrical and mechanical parameters. Differences, if any, relate to internal manufacturing variants or packaging configurations not specified in the provided data.

Q: Will the slightly different dimensions affect my application?

A: The dimensional differences between the 3SBP 300 (0.272" Dia x 1.280" L) and the Littelfuse substitutes (0.275" Dia x 1.275" L) are minimal and within standard tolerances for 3AB/3AG cartridge fuses. These variations do not affect through-hole mounting compatibility or electrical performance.

Q: Why do the Littelfuse parts have lower melting I²t values?

A: The melting I²t parameter (0.73 for Littelfuse vs. 1.85 for Bel Fuse) reflects differences in thermal mass and fuse element design. Lower I²t values indicate faster thermal response. Both values are appropriate for 300 mA slow-blow fuse applications and do not compromise functional equivalence.

Q: Are there any compliance differences I should consider?

A: The 3SBP 300 is RoHS non-compliant, while all three Littelfuse substitutes are ROHS3 compliant. If your application or regulatory environment requires RoHS compliance, the Littelfuse parts are the appropriate choice. Both the original and substitute parts maintain CE, CSA, and UL certifications.

Q: What is the inventory status for these parts?

A: The 3SBP 300 has 642 pieces in stock (obsolete status). The Littelfuse substitutes have higher inventory levels: 0315.300HXP (955 pcs), 0315.300MXP (891 pcs), and 0315.300VXP (953 pcs), all classified as active products.

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