Equivalent & Substitute Parts for BK/S501-1.25-R Ceramic Fuse

Part Overview

The BK/S501-1.25-R is a 1.25 A, 250 V AC ceramic cartridge fuse manufactured by Eaton - Electronics Division. This fast-blow fuse is designed for 5mm x 20mm holder applications and is currently in active production status. Substitute parts are identified to provide design flexibility, supply chain alternatives, and component availability options while maintaining electrical and mechanical compatibility within the specified parameter range.

Substiute Parts

BK/S501-1.25-R

Eaton - Electronics DivisionIn Stock: 930BK/S501-1.25-R Datasheet

Current PartRFQ

02161.25HXP

Littelfuse Inc.In Stock: 854402161.25HXP Datasheet

DirectRFQ

02161.25MXP

Littelfuse Inc.In Stock: 199002161.25MXP Datasheet

DirectRFQ

0001.1005

SCHURTER Inc.In Stock: 19240001.1005 Datasheet

Parametric EquivalentRFQ

FCD-1.25A

OptiFuseIn Stock: 3360FCD-1.25A Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict alignment with the following critical parameters:

Mandatory Matching Parameters:

• Current Rating: 1.25 A (exact match required)
• Voltage Rating (AC): 250 V (exact match required)
• Fuse Type: Cartridge, Ceramic (exact match required)
• Package / Case: 5mm x 20mm (exact match required)
• Response Time: Fast Blow (exact match required)
• Breaking Capacity: 1.5 kA @ Rated Voltage (exact match required)

Compatible Variation Parameters:

• Melting I²t: Variation permitted within 0.313 to 0.538 range
• DC Cold Resistance: Variation permitted within 0.153 to 0.176 Ohms range
• Operating Temperature: Variation permitted; substitute ranges acceptable
• Approval Agencies: Substitute certifications must include at minimum CCC or equivalent

All four substitute parts meet these criteria and are classified as direct functional equivalents.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitute - Direct Manufacturer Equivalents:

The Littelfuse 02161.25HXP and 02161.25MXP are direct functional equivalents with expanded approval agency certifications including CE, CSA, KC, PSE, UL, and VDE. Both parts carry specified operating temperature ranges of -55°C to 125°C and are suitable for applications requiring broader international compliance documentation.

Secondary Substitute - Parametric Equivalent:

The SCHURTER 0001.1005 provides parametric equivalence with certifications including cURus and VDE. This part is suitable for applications where SCHURTER component qualification is required or preferred.

Tertiary Substitute - Parametric Equivalent with DC Rating:

The OptiFuse FCD-1.25A is a parametric equivalent with explicit 250 V DC voltage rating specification. This part is suitable for applications requiring dual AC/DC voltage rating documentation. Approval agency certification is limited to IEC 60127.

All substitute parts maintain active product status and ROHS3 compliance. Selection should be based on specific application requirements, approval agency requirements, and supply chain considerations.

Frequently Asked Questions (FAQ)

Q: Can I substitute BK/S501-1.25-R with any of these parts in my existing design?

A: Yes, all four substitute parts are functionally equivalent within the critical parameters of current rating, voltage rating, fuse type, package size, response time, and breaking capacity. Physical fit in existing 5mm x 20mm fuse holders is guaranteed.

Q: What is the difference between the Littelfuse 02161.25HXP and 02161.25MXP?

A: Both parts are electrically and mechanically identical. The difference lies in series designation and internal construction characteristics. Both are suitable for direct substitution.

Q: Why does the OptiFuse FCD-1.25A specify 250 V DC while others do not?

A: The FCD-1.25A provides explicit DC voltage rating documentation. Other parts may support DC operation but do not specify this parameter in their datasheets. For applications requiring documented DC voltage rating, the FCD-1.25A is the appropriate selection.

Q: Are there any temperature operating range differences I should consider?

A: The BK/S501-1.25-R does not specify an operating temperature range. All substitute parts specify -55°C to 125°C operating range. For applications operating outside standard temperature ranges, verify the original BK/S501-1.25-R specification with Eaton.

Q: What approval agencies are most important for my application?

A: Selection depends on your target market and regulatory requirements. Littelfuse parts offer the broadest certification coverage including UL, CE, CSA, and VDE. SCHURTER offers cURus and VDE. OptiFuse provides IEC 60127 compliance. Verify your specific regulatory requirements before selection.

Q: Can I mix different substitute parts in the same circuit or equipment?

A: All parts meet identical electrical specifications and are mechanically compatible. However, for consistency and supply chain management, using a single part number across a design is recommended.

Q: What is the significance of the Melting I²t variation?

A: Melting I²t values range from 0.313 to 0.538 across all parts. This parameter affects thermal response characteristics. The BK/S501-1.25-R has the lowest value (0.313), indicating faster thermal response. Substitute parts with higher values provide slightly slower thermal response while maintaining fast-blow classification. For applications with specific thermal response requirements, verify compatibility with your circuit design.

Q: Are all parts ROHS3 compliant?

A: Yes, all five parts listed are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory requirements.