Equivalent & Substitute Parts for BK/EFF-400MA

Part Overview

The BK/EFF-400MA is a 400 mA, 250 V AC/DC board mount fuse manufactured by Eaton - Electronics Division, part of the EFF series. This radial, can-style through-hole fuse features fast-blow response characteristics and is designed for circuit protection in electronic applications requiring 400 mA current limitation at 250 V.

The BK/EFF-400MA is classified as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production or repair requirements for systems utilizing this component.

Substiute Parts

BK/EFF-400MA

Eaton - Electronics DivisionIn Stock: 1056BK/EFF-400MA Datasheet

Current PartRFQ

37004000410

Littelfuse Inc.In Stock: 226637004000410 Datasheet

SimilarRFQ

MRF 400-BULK

Bel Fuse Inc.In Stock: 1095MRF 400-BULK Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the BK/EFF-400MA are identified based on strict electrical and mechanical parameter alignment. The following criteria determine substitution eligibility:

Primary Matching Parameters:

• Current Rating: 400 mA (exact match required)
• Voltage Rating (AC): 250 V (exact match required)
• Response Time: Fast Blow (exact match required)
• Mounting Type: Through Hole (exact match required)
• Fuse Type: Board Mount, Radial, Can, Vertical (exact match required)

Secondary Compatibility Parameters:

• Breaking Capacity @ Rated Voltage: 35 A minimum
• Operating Temperature Range: Must encompass or overlap with -55°C ~ 125°C
• Physical Dimensions: Radial, Can, Vertical form factor with compatible PCB footprint

Two substitute parts meet these criteria:

1. 37004000410 (Littelfuse Inc., TR5® 370 series) - Similar manufacturer part number classification
2. MRF 400-BULK (Bel Fuse Inc., MRF series) - Parametric equivalent classification

Both substitutes maintain identical electrical specifications (400 mA, 250 V, Fast Blow) and mechanical form factor (Through Hole, Radial, Can, Vertical) required for direct replacement in the BK/EFF-400MA application.

Parameter Comparison

Engineering Selection Recommendations

37004000410 (Littelfuse Inc., TR5® 370 Series)

This part is classified as a similar manufacturer part number and maintains full electrical equivalence to the BK/EFF-400MA. It is currently in active production status with 2213 units in stock. The part carries expanded regulatory approvals including CCC, cURus, SEMKO, and VDE certifications, providing broader compliance coverage than the original part.

Physical dimensions show minor variation (0.335" Dia x 0.315" H versus 0.329" Dia x 0.303" H), requiring verification of PCB footprint compatibility before implementation. The operating temperature range (-40°C ~ 85°C) is narrower than the original specification (-55°C ~ 125°C), which may limit suitability for applications requiring extended low-temperature operation below -40°C or high-temperature operation above 85°C.

MRF 400-BULK (Bel Fuse Inc., MRF Series)

This part is classified as a parametric equivalent and maintains full electrical equivalence to the BK/EFF-400MA. It is currently in active production status with 1050 units in stock. The part carries comprehensive regulatory approvals including AEC-Q200, CE, CSA, cULus, SEMKO, and VDE certifications, with RoHS3 compliance and REACH unaffected status.

Physical dimensions are identical to the original part (0.329" Dia x 0.303" H), ensuring direct PCB footprint compatibility. The operating temperature range (-55°C ~ 125°C) matches the original specification, supporting applications across the full temperature envelope. Breaking capacity is specified at 35 A, which is lower than the original 50 A rating but remains within acceptable parameters for this current class.

Selection Basis

For applications requiring full temperature range operation (-55°C ~ 125°C) and identical physical dimensions, MRF 400-BULK is the preferred selection. For applications with operating temperature constraints between -40°C and 85°C where minor dimensional variation is acceptable, 37004000410 provides an alternative with expanded regulatory certifications.

Frequently Asked Questions (FAQ)

Q: Can 37004000410 be used as a direct replacement for BK/EFF-400MA without PCB modification?

A: The electrical specifications are fully equivalent. However, physical dimensions differ slightly (0.335" Dia x 0.315" H versus 0.329" Dia x 0.303" H). PCB footprint compatibility must be verified before implementation. If the PCB hole spacing and pad layout accommodate the slightly larger diameter and height, direct replacement is possible without modification.

Q: What is the significance of the melting I²t difference between the three parts?

A: Melting I²t values (0.08, 0.025, and 0.073 respectively) indicate the thermal energy required to melt the fuse element. These variations reflect different internal fuse element designs while maintaining identical 400 mA fast-blow response characteristics. All three parts will interrupt circuit current at the same threshold, but the internal thermal behavior differs slightly. This does not affect substitution eligibility for standard circuit protection applications.

Q: Is MRF 400-BULK suitable for low-temperature applications below -40°C?

A: Yes. MRF 400-BULK specifies an operating temperature range of -55°C ~ 125°C, which encompasses low-temperature operation down to -55°C. The 37004000410 is limited to -40°C minimum and is not suitable for applications requiring operation below -40°C.

Q: What regulatory certifications are most important for industrial applications?

A: Both substitute parts carry SEMKO and VDE certifications, which are standard for European industrial applications. MRF 400-BULK additionally carries AEC-Q200 certification, which is relevant for automotive and high-reliability applications. 37004000410 carries cURus certification, which is relevant for North American applications. Selection should align with the target market and regulatory requirements of the end application.

Q: Are there inventory considerations when selecting between the two substitutes?

A: 37004000410 has 2213 units in stock, while MRF 400-BULK has 1050 units in stock. Both represent adequate inventory levels for production requirements. Selection should prioritize technical compatibility over inventory quantity unless supply chain constraints are a primary concern.