3AP 3 Glass Cartridge Fuse - Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. 3AP 3 is a 3 A, 250 V AC/DC fast-blow glass cartridge fuse with 3AB/3AG package configuration and through-hole mounting. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing system maintenance and new design implementations. Active alternatives from Littelfuse Inc. provide direct functional equivalence while offering improved compliance status.

Substiute Parts

3AP 3

Bel Fuse Inc.In Stock: 9993AP 3 Datasheet

Current PartRFQ

0318003.HXP

Littelfuse Inc.In Stock: 9220318003.HXP Datasheet

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0318003.MXP

Littelfuse Inc.In Stock: 9150318003.MXP Datasheet

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0318003.VXP

Littelfuse Inc.In Stock: 8600318003.VXP Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the 3AP 3 is determined by strict equivalence across the following parameters:

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

The three Littelfuse 318 series variants (0318003.HXP, 0318003.MXP, 0318003.VXP) meet all substitution criteria. These parts are functionally equivalent and mechanically compatible with the original 3AP 3 specification.

Parameter Comparison

Engineering Selection Recommendations

All three Littelfuse 318 series variants (0318003.HXP, 0318003.MXP, 0318003.VXP) are direct functional and mechanical substitutes for the obsolete 3AP 3. Selection among these three variants should be based on packaging availability and inventory requirements, as they are electrically and mechanically identical.

The Littelfuse substitutes offer the following advantages over the original 3AP 3:

• Active product status ensures ongoing availability and supply chain continuity
• ROHS3 compliance addresses environmental and regulatory requirements
• Expanded approval agency certifications (addition of KC certification)
• Identical electrical performance across all critical parameters

Minor dimensional variations (0.003" diameter and 0.008" length differences) and resistance differences (0.0077 Ohms higher) are within acceptable tolerances for cartridge fuse applications and do not affect functional compatibility.

Frequently Asked Questions (FAQ)

Q: Can the Littelfuse 318 series parts directly replace the 3AP 3 in existing applications?

A: Yes. The 0318003.HXP, 0318003.MXP, and 0318003.VXP variants are direct mechanical and electrical substitutes. All critical parameters—current rating, voltage rating, fuse type, response time, package configuration, and mounting type—are identical to the original 3AP 3.

Q: What are the differences between the three Littelfuse substitute options?

A: The 0318003.HXP, 0318003.MXP, and 0318003.VXP variants are electrically and mechanically identical. Differences exist only in packaging configuration and internal construction details not affecting performance. Selection should be based on packaging availability and inventory requirements.

Q: Why does the 3AP 3 have a higher breaking capacity (200 A) than the Littelfuse substitutes (100 A)?

A: Breaking capacity differences reflect design variations between manufacturers. Both ratings exceed typical application requirements for 3 A fuses. Application-specific breaking capacity requirements should be verified against circuit protection specifications.

Q: Are there any compliance or certification differences between the original and substitute parts?

A: The Littelfuse substitutes carry ROHS3 compliance, whereas the original 3AP 3 is RoHS non-compliant. Both maintain equivalent safety certifications (CE, CSA, PSE, UL). The Littelfuse variants add KC certification. For applications requiring RoHS compliance, the Littelfuse substitutes are required.

Q: What is the significance of the melting I²t difference (21 vs. 14)?

A: Melting I²t characterizes thermal response behavior. The lower value in Littelfuse parts indicates slightly faster thermal response. Both values are within the fast-blow fuse classification and maintain equivalent protection characteristics for standard 3 A applications.

Q: Are dimensional differences between parts significant?

A: Dimensional variations (0.003" diameter, 0.008" length) are within standard manufacturing tolerances for cartridge fuses and do not affect mechanical fit or electrical performance in standard through-hole fuse holders.