Bel Fuse Inc. 5MT 125 Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. 5MT 125 is a 125 mA, 250 V AC/DC glass cartridge fuse in 5mm x 20mm form factor, designed for circuit protection in applications requiring medium-blow response characteristics. This fuse requires a holder for installation and operates across a temperature range of -55°C to 125°C. The product is currently obsolete, necessitating identification of active equivalent alternatives that maintain electrical and mechanical compatibility for ongoing system support and new designs.

Substiute Parts

5MT 125

Bel Fuse Inc.In Stock: 11665MT 125 Datasheet

Current PartRFQ

20101250001

Littelfuse Inc.In Stock: 85720101250001 Datasheet

SimilarRFQ

20101250021P

Littelfuse Inc.In Stock: 87720101250021P Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 5MT 125 are identified based on strict electrical and mechanical parameter matching:

Primary Matching Criteria:

• Current Rating: 125 mA (exact match required)
• Voltage Rating (AC): 250 V (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Package / Case: 5mm x 20mm (exact match required)
• Response Time: Medium Blow (exact match required)
• Mounting Type: Requires Holder (exact match required)

The substitute parts listed below satisfy all primary matching criteria and are manufactured by Littelfuse Inc., an established fuse manufacturer. Both substitutes are in active product status, ensuring long-term availability and supply chain continuity.

Parameter Comparison

Engineering Selection Recommendations

Both Littelfuse substitutes (20101250001 and 20101250021P) provide active product status alternatives to the obsolete 5MT 125. The substitutes maintain identical electrical ratings and mechanical form factors, ensuring direct compatibility in existing holder assemblies.

The Littelfuse parts feature higher breaking capacity (80A versus 35A) and lower melting I²t values (0.033 versus 0.04), representing improved performance characteristics. Both substitutes carry cULus certification and are ROHS3 compliant, meeting modern regulatory requirements.

Operating temperature range differs between the original part (-55°C to 125°C) and substitutes (-25°C to 70°C). Applications requiring operation below -25°C or above 70°C must evaluate thermal performance requirements against the substitute specifications.

The choice between 20101250001 and 20101250021P depends on packaging and supply chain requirements, as both parts are electrically and mechanically equivalent.

Frequently Asked Questions (FAQ)

Q: Can the Littelfuse 20101250001 or 20101250021P directly replace the Bel Fuse 5MT 125?

A: Yes. Both Littelfuse parts match the critical electrical parameters (125 mA, 250 V AC, medium-blow response) and mechanical specifications (5mm x 20mm cartridge, requires holder). They install in the same holder assemblies without modification.

Q: What is the difference between Littelfuse 20101250001 and 20101250021P?

A: Both parts are electrically and mechanically identical. The primary difference is packaging designation (Series 201 versus Series 201P). Selection depends on procurement and inventory management requirements.

Q: Does the higher breaking capacity of the Littelfuse substitutes affect circuit protection?

A: No. Breaking capacity defines the maximum fault current the fuse can safely interrupt. Higher breaking capacity (80A versus 35A) provides enhanced safety margin without affecting normal circuit protection at the 125 mA rated current.

Q: Are the Littelfuse substitutes suitable for applications operating below -25°C?

A: The Littelfuse substitutes are rated for -25°C to 70°C operation. Applications requiring operation below -25°C must evaluate alternative fuse options or confirm thermal performance through testing.

Q: What certifications do the substitute parts carry?

A: Both Littelfuse substitutes carry cULus certification. The original Bel Fuse part carried CE, CSA, and cULus certifications. Applications requiring CE or CSA certification must confirm regulatory compliance requirements with system design documentation.

Q: Are the Littelfuse substitutes RoHS compliant?

A: Yes. Both Littelfuse parts are ROHS3 compliant. The original Bel Fuse part is RoHS non-compliant. New designs and systems subject to RoHS requirements should specify the Littelfuse alternatives.