SPXI03.5TXB Equivalent & Substitute Parts

Part Overview

The SPXI03.5TXB is a 3.5A 1.5 kVDC free-hanging inline fuse cartridge manufactured by Littelfuse Inc. as part of the POWR-GARD® SPXI series. This component is designed for solar photovoltaic applications requiring fast-blow response characteristics. The part is currently classified as obsolete, necessitating identification of active equivalent alternatives that maintain identical electrical and mechanical specifications for continued system support and new installations.

Substiute Parts

SPXI03.5TXB

Littelfuse Inc.In Stock: 750SPXI03.5TXB Datasheet

Current PartRFQ

SPXI03.5T

Littelfuse Inc.In Stock: 3022SPXI03.5T Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SPXI03.5TXB is determined by strict equivalence across the following critical parameters:

Electrical Specifications:

• Current Rating: 3.5A (exact match required)
• Voltage Rating: 1.5 kVDC (exact match required)
• Breaking Capacity: 30 kA @ Rated Voltage (exact match required)
• Melting I²t: 25 (exact match required)
• Response Time: Fast Blow (exact match required)

Mechanical Specifications:

• Fuse Type: Cartridge (exact match required)
• Mounting Type: Free Hanging (In-Line) (exact match required)
• Package / Case: Cartridge, Inline, Double Ended (exact match required)

Compliance & Certifications:

• Manufacturer: Littelfuse Inc. (same manufacturer preferred for series consistency)
• Series: POWR-GARD® SPXI (same series required)
• Application: Solar (Photovoltaic) (application-specific requirement)
• RoHS Compliance: Required

The SPXI03.5T qualifies as a direct substitute based on complete alignment with all critical electrical, mechanical, and compliance parameters. Physical dimension variation (length difference) does not affect functional substitution in free-hanging inline mounting configurations where the cartridge is secured at both ends.

Parameter Comparison

Engineering Selection Recommendations

The SPXI03.5T is the direct functional equivalent for the obsolete SPXI03.5TXB. Selection of the SPXI03.5T is based on the following engineering criteria:

Electrical Equivalence: Both parts maintain identical current rating (3.5A), voltage rating (1.5 kVDC), breaking capacity (30 kA), and melting I²t (25), ensuring equivalent protection characteristics in solar photovoltaic circuits.

Mechanical Compatibility: Both parts are cartridge-type, free-hanging inline fuses with double-ended configuration and identical diameter (0.406"). The length variation (3.362" vs. 2.240") does not compromise functional substitution in applications where the cartridge is mechanically secured at both ends within a fuse holder or inline connector assembly.

Product Status & Availability: The SPXI03.5T holds active product status with 3000 units in stock, compared to the obsolete SPXI03.5TXB with limited remaining inventory (664 units). This availability differential supports transition to the active equivalent.

Compliance & Certifications: The SPXI03.5T maintains CE and UR certifications. The main part includes additional gPV and UL certifications. For solar applications requiring gPV or UL certification specifically, compliance verification against system-level requirements is necessary. Both parts are RoHS compliant (ROHS3 for the substitute represents enhanced compliance).

Packaging: The SPXI03.5T is supplied in box packaging (active production standard) versus the main part's unspecified packaging, reflecting the transition from obsolete to active product line.

Frequently Asked Questions (FAQ)

Q: Can the SPXI03.5T directly replace the SPXI03.5TXB in existing solar installations?

A: Yes. Both parts are electrically and mechanically equivalent across all critical parameters: 3.5A current rating, 1.5 kVDC voltage rating, 30 kA breaking capacity, fast-blow response, and cartridge inline mounting. The length difference (2.240" vs. 3.362") does not affect functionality in standard fuse holder assemblies where the cartridge is secured at both ends.

Q: What is the significance of the length difference between these two parts?

A: The SPXI03.5T is shorter (2.240" L) than the SPXI03.5TXB (3.362" L), but both maintain identical diameter (0.406"). In free-hanging inline mounting configurations, the cartridge is mechanically secured at both ends within a connector or holder assembly. The length variation reflects manufacturing evolution within the same product series and does not impact electrical performance or mechanical compatibility in standard installations.

Q: Are there certification differences between the SPXI03.5TXB and SPXI03.5T?

A: The SPXI03.5TXB carries CE, gPV, UL, and UR certifications. The SPXI03.5T carries CE and UR certifications. For applications requiring gPV or UL certification specifically, system-level compliance documentation should be reviewed. Both parts meet RoHS requirements (ROHS3 for the substitute represents current compliance standard).

Q: Why is the SPXI03.5TXB classified as obsolete?

A: The SPXI03.5TXB is obsolete due to product line consolidation within the POWR-GARD® SPXI series. The SPXI03.5T represents the active production equivalent, offering identical electrical and mechanical specifications with improved availability and current manufacturing standards.

Q: What inventory considerations apply to this substitution?

A: The SPXI03.5TXB has 664 units remaining in stock (obsolete status). The SPXI03.5T has 3000 units in stock (active status). For new designs and ongoing production, the SPXI03.5T is the recommended selection based on availability and active product support.

Q: Are there any DC cold resistance or thermal characteristics I should verify?

A: The SPXI03.5TXB specifies DC cold resistance of 0.0711 Ohms. The SPXI03.5T does not provide this specification in available documentation. Both parts share identical melting I²t (25), which determines thermal protection characteristics. For applications where DC cold resistance is a critical design parameter, direct confirmation with Littelfuse Inc. is recommended.

Q: Can the SPXI03.5T be used in applications originally designed for the SPXI03.5TXB?

A: Yes. The SPXI03.5T is a direct substitute for the SPXI03.5TXB in all solar photovoltaic applications. Both parts are rated for 1.5 kVDC systems with 3.5A protection, fast-blow response, and 30 kA breaking capacity. No circuit redesign or system modification is required.