3AP 500 Equivalent & Substitute Parts

Part Overview

The 3AP 500 is a 500 mA, 250 V AC/DC fast-blow glass cartridge fuse manufactured by Bel Fuse Inc. in the 3AB/3AG package format (1/4" x 1-1/4" axial). This component is classified as obsolete, making equivalent substitute parts necessary for ongoing system maintenance and new design implementations. Active alternatives from Littelfuse Inc. and Eaton Electronics Division provide direct functional equivalence while offering improved availability and compliance status.

Key Parameters

Parameter	Value
Current Rating	500 mA
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (Axial)
Response Time	Fast Blow
Mounting Type	Through Hole
Operating Temperature Range	-55°C ~ 125°C

Substitute Part Grouping Explanation

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

Current Rating: 500 mA (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: Fast Blow (exact match required)
Mounting Type: Through Hole (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 breaking capacity, melting I²t, DC cold resistance, and approval agency certifications do not disqualify substitution but may influence selection based on application-specific requirements.

Parameter Comparison

Parameter	3AP 500 (Bel Fuse)	0318.500HXP (Littelfuse)	0318.500MXP (Littelfuse)	0318.500VXP (Littelfuse)	BK/AGC-V-1/2 (Eaton)
Current Rating (Amps)	500 mA	500 mA	500 mA	500 mA	500 mA
Voltage Rating - AC	250 V	250 V	250 V	250 V	250 V
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"
Response Time	Fast Blow	Fast Blow	Fast Blow	Fast Blow	Fast Blow
Mounting Type	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
Breaking Capacity @ Rated Voltage	200A	35A	35A	35A	35A
Melting I²t	0.14	0.483	0.483	0.483	0.385
DC Cold Resistance (Ohms)	1.28	0.498	0.498	0.498	0.483
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	RoHS non-compliant
Approval Agency	CE, CSA, PSE, UL	CE, CSA, UL	CE, CSA, UL	CE, CSA, UL	CSA, UL

Engineering Selection Recommendations

Littelfuse 0318.500HXP, 0318.500MXP, 0318.500VXP: These three part numbers are functionally identical substitutes with active product status and ROHS3 compliance. All three carry CE, CSA, and UL certifications. Selection among these variants should be based on packaging availability (all listed as Bulk) and inventory requirements. The Littelfuse series offers superior RoHS compliance compared to the obsolete 3AP 500.

Eaton BK/AGC-V-1/2: This part provides an active alternative with CSA and UL certifications. It maintains RoHS non-compliant status, matching the original 3AP 500 in this regard. The Eaton AGC series offers a lower melting I²t value (0.385) compared to Littelfuse alternatives (0.483), which may be relevant for applications with specific thermal response requirements.

For new designs and systems requiring RoHS compliance, Littelfuse 318 series parts are preferred. For legacy system maintenance where RoHS compliance is not mandated, all four substitutes provide equivalent electrical and mechanical functionality.

Frequently Asked Questions (FAQ)

Q: Can the Littelfuse 0318.500HXP, 0318.500MXP, and 0318.500VXP be used interchangeably?

A: Yes. All three Littelfuse part numbers are electrically and mechanically equivalent. They share identical current rating, voltage rating, package dimensions, response time, and operating temperature range. Selection should be based on packaging format and inventory availability.

Q: What is the significance of the different melting I²t values between the 3AP 500 and its substitutes?

A: The melting I²t parameter defines the thermal energy required to melt the fuse element. The 3AP 500 has a melting I²t of 0.14, while Littelfuse alternatives have 0.483 and Eaton has 0.385. These differences affect the fuse's response to transient overcurrent conditions. Applications with specific thermal response requirements should account for this variation.

Q: Are all substitute parts approved for the same regulatory standards?

A: The 3AP 500 carries CE, CSA, PSE, and UL certifications. Littelfuse 318 series parts carry CE, CSA, and UL certifications (PSE not listed). Eaton BK/AGC-V-1/2 carries CSA and UL certifications (CE and PSE not listed). Verify that substitute part certifications meet your application's regulatory requirements.

Q: What is the difference between RoHS3 compliant and RoHS non-compliant status?

A: ROHS3 compliance indicates the part meets the Restriction of Hazardous Substances Directive requirements. The 3AP 500 and Eaton BK/AGC-V-1/2 are RoHS non-compliant, while all Littelfuse 318 series parts are ROHS3 compliant. For applications subject to RoHS regulations, Littelfuse alternatives are required.

Q: Can the 3AB and 3AG package designations be used interchangeably?

A: Both designations refer to the same physical package format (1/4" x 1-1/4" axial). The terms are equivalent in this context and indicate the same mechanical compatibility.

Q: How do the physical dimensions compare between the main part and substitutes?

A: The 3AP 500 measures 0.272" Dia x 1.280" L (6.90mm x 32.50mm). Littelfuse alternatives measure 0.275" Dia x 1.288" L (6.99mm x 32.72mm). Eaton measures 0.266" Dia x 1.292" L (6.76mm x 32.82mm). These minor dimensional variations remain within the 3AB/3AG package specification and do not affect mechanical compatibility in standard through-hole applications.

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