Equivalent & Substitute Parts for MQ 3TR Board Mount Fuse

Part Overview

The MQ 3TR is a 3A 125VAC/125VDC board mount axial fuse manufactured by Bel Fuse Inc. This component is classified as obsolete, making substitute parts necessary for new designs and ongoing production requirements. The MQ 3TR serves as a protection device in low-voltage AC/DC circuits requiring fast-blow response characteristics and through-hole mounting configuration.

Key Parameters

Parameter	Value
Current Rating	3 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Fast Blow
Mounting Type	Through Hole
Fuse Type	Board Mount (Cartridge Style Excluded)
Package / Case	Axial
Breaking Capacity @ Rated Voltage	50A AC, 300A DC
Operating Temperature Range	-55°C ~ 125°C

Substitute Part Grouping Explanation

Substitution for the MQ 3TR is determined by strict equivalence across the following electrical and mechanical parameters:

Current Rating: 3 A (exact match required)
Voltage Rating: 125 V AC and 125 V DC (exact match required)
Response Time: Fast Blow (exact match required)
Mounting Type: Through Hole (exact match required)
Fuse Type: Board Mount, Axial configuration (exact match required)
Breaking Capacity: 50A AC, 300A DC (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

The substitute parts identified—0251003.MXL and 0251003.NRT1L from Littelfuse Inc.—meet all electrical specifications and mechanical requirements. Both are PICO® II 251 series components with active product status, ensuring long-term availability and supply chain reliability.

Parameter Comparison

Parameter	MQ 3TR (Bel Fuse)	0251003.MXL (Littelfuse)	0251003.NRT1L (Littelfuse)
Current Rating (Amps)	3 A	3 A	3 A
Voltage Rating - AC	125 V	125 V	125 V
Voltage Rating - DC	125 V	125 V	125 V
Response Time	Fast Blow	Fast Blow	Fast Blow
Mounting Type	Through Hole	Through Hole	Through Hole
Fuse Type	Board Mount (Cartridge Style Excluded)	Board Mount (Cartridge Style Excluded)	Board Mount (Cartridge Style Excluded)
Package / Case	Axial	Axial	Axial
Breaking Capacity @ Rated Voltage	50A AC, 300A DC	50A AC, 300A DC	50A AC, 300A DC
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
DC Cold Resistance	0.028 Ohms	0.0295 Ohms	0.0295 Ohms
Melting I²t	1.1	1.19	1.19
Product Status	Obsolete	Active	Active
Approval Agency	CE, CSA, cURus	CCC, CSA, cURus, PSE, TUV	CCC, CSA, cURus, PSE, TUV
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant
Size / Dimension	0.125" Dia x 0.280" L (3.18mm x 7.10mm)	0.110" Dia x 0.280" L (2.80mm x 7.11mm)	0.110" Dia x 0.280" L (2.80mm x 7.11mm)

Engineering Selection Recommendations

Both 0251003.MXL and 0251003.NRT1L are functionally equivalent to the MQ 3TR across all critical electrical parameters. The primary distinction between the two Littelfuse substitutes is packaging format:

0251003.MXL is supplied in Bulk packaging, suitable for high-volume manufacturing environments where component handling and storage infrastructure supports loose component management.

0251003.NRT1L is supplied in Cut Tape (CT) packaging, appropriate for automated pick-and-place assembly processes and applications requiring controlled component dispensing.

Both substitute parts carry active product status from Littelfuse Inc., ensuring sustained manufacturing support and supply chain continuity. The Littelfuse components provide expanded regulatory compliance certifications (CCC, PSE, TUV) beyond the original MQ 3TR approvals, and both are ROHS3 compliant.

Minor dimensional variations exist: the Littelfuse parts feature a 0.110" diameter versus the MQ 3TR's 0.125" diameter. This reduction in body diameter does not affect electrical performance or through-hole mounting compatibility, as the axial lead configuration remains functionally identical.

Frequently Asked Questions (FAQ)

Q: Can 0251003.MXL and 0251003.NRT1L be used interchangeably with the MQ 3TR?

A: Yes. Both Littelfuse parts meet all electrical and mechanical specifications required for direct substitution. The difference between them is packaging format only; electrical performance is identical.

Q: What is the difference between 0251003.MXL and 0251003.NRT1L?

A: Both parts are electrically identical 3A 125VAC/125VDC fast-blow fuses. The difference is packaging: 0251003.MXL comes in Bulk format, while 0251003.NRT1L comes in Cut Tape (CT) format. Select based on your assembly process requirements.

Q: Are there dimensional compatibility concerns with the smaller diameter Littelfuse parts?

A: No. The Littelfuse substitutes have a 0.110" diameter compared to the MQ 3TR's 0.125" diameter. This smaller diameter does not affect through-hole mounting or electrical performance. The axial lead configuration remains compatible with standard PCB footprints designed for 3A axial fuses.

Q: Do the substitute parts have better regulatory compliance than the original MQ 3TR?

A: Yes. Both 0251003.MXL and 0251003.NRT1L carry expanded certifications (CCC, CSA, cURus, PSE, TUV) and are ROHS3 compliant, providing broader regulatory coverage than the original part.

Q: What is the significance of the melting I²t difference (1.1 vs 1.19)?

A: The melting I²t values are within acceptable tolerance for fast-blow fuse substitution. Both values confirm fast-blow response characteristics suitable for circuit protection in the specified voltage and current range.

Q: Which substitute should I select for new production designs?

A: For automated assembly processes, select 0251003.NRT1L (Cut Tape). For manual assembly or high-volume loose component handling, select 0251003.MXL (Bulk). Both are electrically and mechanically equivalent.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message