Equivalent & Substitute Parts for 3JS 250-R

Part Overview

The 3JS 250-R is a 250 mA slow-blow glass cartridge fuse manufactured by Bel Fuse Inc., rated for 350 V AC and 140 V DC operation. This component is classified as obsolete, necessitating identification of active substitute parts to maintain circuit protection functionality in applications requiring equivalent electrical and mechanical specifications. The 2AG form factor (5mm x 15mm axial) and slow-blow response time are critical parameters for substitute selection.

Substiute Parts

3JS 250-R

Bel Fuse Inc.In Stock: 9553JS 250-R Datasheet

Current PartRFQ

0209.250MXEP

Littelfuse Inc.In Stock: 27880209.250MXEP Datasheet

SimilarRFQ

0230.250MXP

Littelfuse Inc.In Stock: 24260230.250MXP Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 3JS 250-R are selected based on the following critical parameters that must align with the original specification:

Mandatory Matching Parameters:

• Current Rating: 250 mA (exact match required)
• Response Time: Slow Blow (exact match required)
• Mounting Type: Through Hole (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Operating Temperature Range: -55°C ~ 125°C (minimum requirement)

Voltage Rating Considerations:

• AC Voltage: Substitute must meet or exceed 350 V AC
• DC Voltage: Substitute must meet or exceed 140 V DC

Physical Form Factor:

• Package compatibility with 2AG or equivalent axial cartridge dimensions

Two active substitute parts meet these criteria: the Littelfuse 0209.250MXEP and the Littelfuse 0230.250MXP. Both maintain the 250 mA current rating, slow-blow response, and through-hole mounting configuration required for direct functional replacement.

Parameter Comparison

Engineering Selection Recommendations

0209.250MXEP (Littelfuse) is the primary substitute for applications operating at 350 V AC. This part maintains identical current rating, response time, and standard 2AG form factor. It holds active product status with CE and cULus certifications. The DC voltage rating is not specified in the provided data; applications requiring 140 V DC operation must confirm DC compatibility through manufacturer documentation.

0230.250MXP (Littelfuse) is suitable for applications operating at reduced voltage levels (250 V AC maximum, 125 V DC maximum). This part maintains the 250 mA current rating and slow-blow response but features a non-standard cartridge form factor. It holds active product status with CE, CSA, and UL certifications, providing broader regulatory coverage than the main part.

Both substitutes are ROHS3 compliant and operate across the required temperature range. Selection between these options depends on the specific voltage requirements of the target application.

Frequently Asked Questions (FAQ)

Q: Can the 0209.250MXEP directly replace the 3JS 250-R in all applications?

A: The 0209.250MXEP matches the 3JS 250-R in current rating (250 mA), response time (slow-blow), and AC voltage rating (350 V). However, the DC voltage rating for the 0209.250MXEP is not specified in the provided data. Applications requiring 140 V DC operation must verify DC compatibility with the manufacturer before substitution.

Q: What is the difference between the two substitute parts?

A: The primary difference is voltage rating. The 0209.250MXEP is rated for 350 V AC (matching the original part), while the 0230.250MXP is rated for 250 V AC and 125 V DC. Additionally, the 0209.250MXEP uses the standard 2AG form factor, while the 0230.250MXP uses a non-standard cartridge form factor. Both maintain the 250 mA current rating and slow-blow response.

Q: Are there physical compatibility concerns with the non-standard form factor of the 0230.250MXP?

A: The 0230.250MXP uses a non-standard cartridge form factor (4.50mm diameter x 14.50mm length) compared to the standard 2AG form factor of the original part (5.50mm diameter x 15.00mm length). Physical compatibility with existing fuse holders must be confirmed before substitution.

Q: Do both substitute parts meet the same regulatory certifications as the original?

A: The 0209.250MXEP holds CE and cULus certifications. The 0230.250MXP holds CE, CSA, and UL certifications. The original 3JS 250-R holds CE, CSA, and cURus certifications. Application-specific regulatory requirements determine which substitute is appropriate.

Q: What is the significance of the Melting I²t difference between the original and substitutes?

A: The original 3JS 250-R has a Melting I²t of 0.41, while both Littelfuse substitutes have a Melting I²t of 0.216. This parameter affects the thermal response characteristics of the fuse. Applications with specific thermal requirements must confirm compatibility with the substitute's thermal profile.