3AG 5 Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The 3AG 5 is a 5 A, 250 V AC/DC fast-blow glass cartridge fuse manufactured by Bel Fuse Inc. in the 3AG series. This component is classified as obsolete, which necessitates identification of active equivalent and substitute parts for ongoing design support and procurement. The fuse is designed for use with 3AB and 3AG holders and operates across a temperature range of -55°C to 125°C with a breaking capacity of 200 A at rated voltage.

Key Parameters

Parameter	Value
Current Rating	5 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Response Time	Fast Blow
Package / Case	3AB, 3AG, 1/4" x 1-1/4"
Breaking Capacity @ Rated Voltage	200 A
Operating Temperature Range	-55°C ~ 125°C
Mounting Type	Requires Holder

Substitute Part Grouping Explanation

Substitution of the 3AG 5 is determined by strict equivalence across the following parameters: current rating (5 A), voltage rating (250 V AC), fuse type (cartridge glass), response time (fast blow), physical package dimensions (1/4" x 1-1/4"), and compatibility with 3AB and 3AG holders. All identified substitutes maintain these core electrical and mechanical specifications. Substitutes are grouped as follows:

Direct Manufacturer Equivalent: 3AG 5-R (Bel Fuse Inc.) — same manufacturer, active product status, identical electrical specifications with improved RoHS3 compliance.

Similar Manufacturer Equivalent: 0312005.MXP (Littelfuse Inc.) — alternative manufacturer, active status, equivalent electrical performance within the 312 series.

Parametric Equivalent: FSA-5A (OptiFuse) — alternative manufacturer, active status, matching electrical and dimensional specifications within the FSA series.

Parameter Comparison

Parameter	3AG 5	3AG 5-R	0312005.MXP	FSA-5A
Manufacturer	Bel Fuse Inc.	Bel Fuse Inc.	Littelfuse Inc.	OptiFuse
Current Rating (Amps)	5 A	5 A	5 A	5 A
Voltage Rating - AC	250 V	250 V	250 V	250 V
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
Response Time	Fast Blow	Fast Blow	Fast Blow	Fast Blow
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"
Breaking Capacity @ Rated Voltage	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
Product Status	Obsolete	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
DC Cold Resistance (Ohms)	0.02	0.018	0.0224	Not specified
Melting I²t	63	63	50	72.54

Engineering Selection Recommendations

3AG 5-R (Bel Fuse Inc.): This is the primary recommended substitute. It is manufactured by the same supplier as the original part, maintains identical electrical specifications, and carries active product status with ROHS3 compliance. The DC cold resistance is marginally lower (0.018 Ω vs. 0.02 Ω), which is within acceptable tolerance for this component class.

0312005.MXP (Littelfuse Inc.): This substitute is suitable for applications requiring multi-source qualification. It maintains all critical electrical parameters and holds active status with ROHS3 compliance. The melting I²t value (50) is lower than the original (63), which may affect response characteristics in marginal overcurrent conditions. Approval agencies include CE, CSA, KC, PSE, and UL.

FSA-5A (OptiFuse): This substitute provides an alternative from a third manufacturer with active product status and ROHS3 compliance. The melting I²t value (72.54) is higher than the original, resulting in a slightly slower response to overcurrent. Approval is limited to cULus and UL 248. This option is suitable for applications where OptiFuse qualification is required.

Frequently Asked Questions (FAQ)

Q: Can 3AG 5-R be used as a direct replacement for 3AG 5?

A: Yes. The 3AG 5-R maintains identical electrical specifications (5 A, 250 V AC, fast-blow response) and physical dimensions (1/4" x 1-1/4"). Both are compatible with 3AB and 3AG holders. The primary advantage is active product status and improved RoHS3 compliance.

Q: What is the difference between the melting I²t values across substitutes?

A: Melting I²t indicates the thermal energy required to melt the fuse element. The original 3AG 5 has an I²t of 63. The 0312005.MXP (I²t = 50) will respond faster to sustained overcurrent, while FSA-5A (I²t = 72.54) will respond more slowly. Selection depends on circuit protection requirements.

Q: Are all substitutes compatible with existing 3AG and 3AB holders?

A: Yes. All substitutes maintain the 1/4" x 1-1/4" physical dimensions and are designed for use with 3AB and 3AG holders.

Q: Which substitute has the best compliance certifications?

A: The 0312005.MXP (Littelfuse Inc.) carries the broadest approval agency coverage: CE, CSA, KC, PSE, and UL. The 3AG 5-R includes CE, CSA, cURus, and PSE. The FSA-5A is limited to cULus and UL 248.

Q: Is RoHS compliance a factor in selecting a substitute?

A: The original 3AG 5 is RoHS non-compliant. All three substitutes are ROHS3 compliant, making them suitable for applications with RoHS requirements.

Q: What is the DC cold resistance significance?

A: DC cold resistance affects voltage drop across the fuse during normal operation. The 3AG 5-R (0.018 Ω) has the lowest resistance, followed by the original (0.02 Ω) and 0312005.MXP (0.0224 Ω). Differences are minimal for this current rating.

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