Equivalent & Substitute Parts for 3AP 4 Glass Cartridge Fuse

Part Overview

The Bel Fuse Inc. 3AP 4 is a 4 A, 250 V AC/DC fast-blow glass cartridge fuse in 3AB/3AG package format (1/4" x 1-1/4" axial). This component is classified as obsolete, making equivalent substitutes necessary for ongoing system maintenance and new designs. Direct replacements from active manufacturers ensure continued availability and compliance with current regulatory standards.

Key Parameters

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

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence across the following parameters:

Current Rating: 4 A (exact match required)
Voltage Rating (AC): 250 V (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Response Time: Fast 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: 200 A (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

All substitute parts listed meet these criteria. Variations in secondary parameters such as melting I²t, DC cold resistance, and dimensional tolerances remain within acceptable engineering margins for this product category.

Parameter Comparison

Parameter	3AP 4 (Bel Fuse)	0318004.HXP (Littelfuse)	0318004.MXP (Littelfuse)	0318004.VXP (Littelfuse)	BK/AGC-BV-4 (Eaton)	BK/AGC-V-4 (Eaton)
Current Rating (Amps)	4 A	4 A	4 A	4 A	4 A	4 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	Fast Blow	Fast Blow	Fast Blow	Fast Blow	Fast Blow	Fast 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
Breaking Capacity @ Rated Voltage	200 A	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	-55°C ~ 125°C
Product Status	Obsolete	Active	Active	Active	Active	Active
Approval Agency	CE, CSA, PSE, UL	CE, CSA, KC, PSE, UL	CE, CSA, KC, PSE, UL	CE, CSA, KC, PSE, UL	CSA, UL	CSA, UL
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	RoHS non-compliant	RoHS non-compliant

Engineering Selection Recommendations

All listed substitute parts are electrically and mechanically equivalent to the 3AP 4. Selection should be based on the following criteria:

Direct Substitutes (Littelfuse 318 Series): The 0318004.HXP, 0318004.MXP, and 0318004.VXP are active products with ROHS3 compliance and expanded approval agency certifications (CE, CSA, KC, PSE, UL). These are preferred for new designs and applications requiring RoHS compliance.

Alternative Substitutes (Eaton AGC Series): The BK/AGC-BV-4 and BK/AGC-V-4 are active products with CSA and UL certifications. These are suitable for applications where RoHS compliance is not required and existing AGC series inventory is preferred.

Frequently Asked Questions (FAQ)

Q: Can the Littelfuse 0318004.HXP, 0318004.MXP, and 0318004.VXP be used interchangeably?

A: Yes. All three Littelfuse parts share identical electrical ratings, mechanical dimensions, and performance characteristics. Selection between them may be based on packaging availability or internal inventory management.

Q: What is the difference between the Littelfuse 318 series and Eaton AGC series substitutes?

A: Both meet the core electrical and mechanical requirements. The Littelfuse 318 series offers ROHS3 compliance and broader approval certifications. The Eaton AGC series provides an alternative with CSA and UL certifications. Melting I²t values differ (28.5 for Littelfuse, 86.56 for Eaton), reflecting different thermal response characteristics within the fast-blow classification.

Q: Is the 3AP 4 still available?

A: The 3AP 4 is classified as obsolete. Active substitutes from Littelfuse and Eaton are recommended for continued system support and new applications.

Q: Are dimensional tolerances critical for substitution?

A: All substitute parts conform to the 3AB/3AG package standard with 1/4" x 1-1/4" axial dimensions. Minor dimensional variations (0.272" to 0.275" diameter, 1.280" to 1.292" length) remain within standard package tolerances and do not affect mechanical fit or electrical performance in standard fuse holders.

Q: Which substitute is recommended for RoHS-compliant applications?

A: The Littelfuse 318 series (0318004.HXP, 0318004.MXP, 0318004.VXP) are ROHS3 compliant and suitable for applications requiring RoHS certification.

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