3SB 7 Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The 3SB 7 is a 7 A, 250 V AC/DC slow-blow glass cartridge fuse manufactured by Bel Fuse Inc. in the 3AB/3AG package format (1/4" x 1-1/4"). This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing system maintenance and new design implementations. The fuse requires a compatible holder for installation and is designed for general-purpose circuit protection applications requiring slow-blow response characteristics.

Key Parameters

Parameter	Value
Current Rating	7 A
Voltage Rating (AC)	250 V
Response Time	Slow Blow
Fuse Type	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4"
Breaking Capacity @ Rated Voltage	200 A
Operating Temperature Range	-55°C ~ 125°C
Size / Dimension	0.250" Dia x 1.250" - 1.252" L

Substitute Part Grouping Explanation

Substitution for the 3SB 7 is determined by strict equivalence across the following critical parameters:

Current Rating: 7 A (exact match required)
Voltage Rating: 250 V AC (exact match required)
Response Time: Slow Blow (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (exact match required)
Breaking Capacity: 200 A (exact match required)
Operating Temperature: -55°C ~ 125°C (exact match required)

All substitute parts listed below meet these electrical and mechanical parameters. Substitutes are grouped by manufacturer and product status to facilitate selection based on availability and compliance requirements.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Current Rating (A)	Voltage Rating (V AC)	Response Time	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ohms)	Product Status	RoHS Status	Approval Agency
3SB 7	Bel Fuse Inc.	7	250	Slow Blow	200	372	0.016	Obsolete	RoHS non-compliant	CE, CSA, PSE, UL
3SB 7-R	Bel Fuse Inc.	7	250	Slow Blow	200	372	0.016	Active	ROHS3 Compliant	CE, CSA, cULus, PSE
0034.5243	SCHURTER Inc.	7	250	Slow Blow	200	Not specified	Not specified	Obsolete	ROHS3 Compliant	CSA, UL
0313007.HXP	Littelfuse Inc.	7	250	Slow Blow	200	347	0.0128	Active	ROHS3 Compliant	CE, CSA, K-MARK, PSE, UL
0313007.MXP	Littelfuse Inc.	7	250	Slow Blow	200	347	0.0128	Active	ROHS3 Compliant	CE, CSA, K-MARK, PSE, UL
0313007.VXP	Littelfuse Inc.	7	250	Slow Blow	200	347	0.0128	Active	CE, CSA, KC, PSE, UL	ROHS3 Compliant
0313007.HXIDP	Littelfuse Inc.	7	250	Slow Blow	200	347	0.0128	Active	ROHS3 Compliant	CE, CSA, K-MARK, PSE, UL
0313007.VXIDP	Littelfuse Inc.	7	250	Slow Blow	200	347	0.0128	Active	ROHS3 Compliant	CE, CSA, KC, PSE, UL
TSA-7A	OptiFuse	7	250	Slow Blow	200	981	Not specified	Active	ROHS3 Compliant	cULus, UL 248

Engineering Selection Recommendations

For applications requiring replacement of the obsolete 3SB 7, the following selection criteria apply:

Active Product Status Priority: 3SB 7-R (Bel Fuse Inc.) provides direct manufacturer continuity with active product status and ROHS3 compliance. This part maintains identical electrical parameters and mechanical compatibility while offering improved regulatory compliance over the original obsolete part.

Littelfuse 313 Series (0313007.HXP, 0313007.MXP, 0313007.VXP, 0313007.HXIDP, 0313007.VXIDP): All variants meet the required electrical and mechanical specifications with active product status and ROHS3 compliance. These parts are widely available and carry comprehensive international approvals including CE, CSA, PSE, and UL certifications. Variants differ in approval agency coverage (K-MARK vs. KC) and packaging designations but are electrically and mechanically equivalent.

SCHURTER 0034.5243: Meets all electrical and mechanical parameters with ROHS3 compliance. Product status is obsolete, limiting long-term availability.

OptiFuse TSA-7A: Meets all electrical and mechanical parameters with active product status and ROHS3 compliance. Carries UL 248 and cULus approvals. Note: Melting I²t value (981) differs from other substitutes, indicating different thermal response characteristics within the slow-blow classification.

Regulatory Compliance: For new designs or systems requiring RoHS compliance, all active substitutes (3SB 7-R, Littelfuse 313 series, TSA-7A) are ROHS3 compliant. The original 3SB 7 is RoHS non-compliant.

Frequently Asked Questions (FAQ)

Q: Can I use any of these substitute parts interchangeably with the 3SB 7?

A: Yes, all listed substitute parts meet the required electrical parameters (7 A, 250 V AC, slow-blow response, 200 A breaking capacity) and mechanical specifications (3AB/3AG package, 1/4" x 1-1/4" dimensions). Physical installation compatibility is identical across all substitutes.

Q: What is the difference between the Littelfuse variants (HXP, MXP, VXP, HXIDP, VXIDP)?

A: All Littelfuse 313 series variants listed are electrically and mechanically equivalent. Designations reflect different approval agency certifications and packaging configurations. Selection among these variants should be based on specific regulatory requirements for your application region.

Q: Why does the OptiFuse TSA-7A have a different Melting I²t value?

A: Melting I²t (347 for Littelfuse, 372 for Bel Fuse 3SB 7, 981 for OptiFuse TSA-7A) represents the thermal energy required to melt the fuse element. All parts maintain the same slow-blow response classification and 7 A current rating. The difference reflects manufacturing design variations within the slow-blow category but does not affect compatibility for applications designed around the 7 A, 250 V, slow-blow specification.

Q: Is the 3SB 7-R a direct replacement for the obsolete 3SB 7?

A: Yes. The 3SB 7-R is the active product continuation from Bel Fuse Inc. with identical electrical and mechanical specifications. It provides direct manufacturer continuity with improved RoHS compliance.

Q: Which substitute should I choose for new designs?

A: For new designs, select from active products with ROHS3 compliance: 3SB 7-R, Littelfuse 313 series (any variant), or TSA-7A. Choice should be based on supply chain availability, regional approval requirements, and established vendor relationships.

Q: Do all these fuses require the same holder?

A: Yes. All substitute parts use the 3AB/3AG package format (1/4" x 1-1/4") and are compatible with holders designed for this standard package specification.

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