SCHURTER 0034.3987 Glass Cartridge Fuse 1A 250VAC 5x20mm Equivalent & Substitute Parts

Part Overview

The SCHURTER 0034.3987 is a 1 A, 250 V AC/DC slow-blow glass cartridge fuse in 5mm x 20mm form factor, designed for applications requiring holder-mounted fuse protection. This part is classified as obsolete. Due to its discontinued status, equivalent active alternatives from SCHURTER and direct substitutes from Littelfuse Inc. are available to maintain circuit protection functionality in existing designs and new production builds.

Key Parameters

Parameter	Value
Current Rating	1 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Response Time	Slow Blow
Package / Case	5mm x 20mm
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	35 A
Size / Dimension	0.205" Dia x 0.787" L (5.20mm x 20.00mm)
RoHS Status	ROHS3 Compliant
REACH Status	REACH Unaffected

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence across the following parameters:

Current Rating: 1 A (exact match required)
Voltage Rating (AC): 250 V (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Response Time: Slow Blow (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Mounting Type: Requires Holder (exact match required)
Breaking Capacity @ Rated Voltage: 35 A (exact match required)

All substitute parts listed meet these core electrical and mechanical parameters. Differences in melting I²t values, operating temperature ranges, and approval agencies are noted but do not disqualify substitution when the above criteria are satisfied.

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating	Voltage Rating (AC)	Response Time	Package / Case	Breaking Capacity	Melting I²t	Product Status	Operating Temperature	Approval Agency
0034.3987	SCHURTER Inc.	FSD 5x20	1 A	250 V	Slow Blow	5mm x 20mm	35 A	10.6	Obsolete	—	CSA, UL
0034.3117	SCHURTER Inc.	FST 5x20	1 A	250 V	Slow Blow	5mm x 20mm	35 A	3.3	Active	-55°C ~ 125°C	CCC, cURus, PSE/JET, VDE
0034.3117.G	SCHURTER Inc.	FST 5x20	1 A	250 V	Slow Blow	5mm x 20mm	35 A	3.3	Active	-55°C ~ 125°C	CCC, cURus, PSE/JET, VDE
0034.3775	SCHURTER Inc.	FSL 5x20	1 A	250 V	Slow Blow	5mm x 20mm	35 A	4.52	Active	-40°C ~ 85°C	cULus
0034.5043	SCHURTER Inc.	FTT 5x20	1 A	250 V	Slow Blow	5mm x 20mm	35 A	19.4	Active	-40°C ~ 85°C	cURus
0034.5617.11	SCHURTER Inc.	SMD-FST	1 A	250 V	Slow Blow	5mm x 20mm	35 A	3.3	Active	-55°C ~ 125°C	cURus, VDE
0034.5713.11	SCHURTER Inc.	SMD-FTT	1 A	250 V	Slow Blow	5mm x 20mm	35 A	19.4	Active	-55°C ~ 125°C	cURus
0239001.HXP	Littelfuse Inc.	239	1 A	250 V	Slow Blow	5mm x 20mm	35 A	11.295	Active	-55°C ~ 125°C	CE, CSA, KC, PSE, UL
0239001.MXP	Littelfuse Inc.	239	1 A	250 V	Slow Blow	5mm x 20mm	35 A	11.295	Active	-55°C ~ 125°C	CE, CSA, KC, PSE, UL
0239001.TXP	Littelfuse Inc.	239	1 A	250 V	Slow Blow	5mm x 20mm	35 A	11.295	Active	-55°C ~ 125°C	CE, CSA, KC, PSE, UL
0239001.VXP	Littelfuse Inc.	239	1 A	250 V	Slow Blow	5mm x 20mm	35 A	11.295	Active	-55°C ~ 125°C	CE, CSA, KC, PSE, UL

Engineering Selection Recommendations

All listed substitute parts satisfy the core electrical and mechanical requirements for direct replacement of the SCHURTER 0034.3987. Selection should prioritize active product status and compliance certifications relevant to the target application.

SCHURTER active alternatives (0034.3117, 0034.3117.G, 0034.3775, 0034.5043, 0034.5617.11, 0034.5713.11) maintain manufacturer continuity and are available in higher inventory quantities. These parts carry expanded approval certifications including CCC, PSE/JET, and VDE, supporting broader regional compliance requirements.

Littelfuse 239 series parts (0239001.HXP, 0239001.MXP, 0239001.TXP, 0239001.VXP) provide cross-manufacturer equivalence with active status and comprehensive global certifications (CE, CSA, KC, PSE, UL). These parts are suitable for applications requiring multi-source qualification or where Littelfuse supply chain integration is preferred.

Operating temperature range and melting I²t characteristics vary across substitutes. Applications with specific thermal or response-time requirements should reference the detailed parameter table to confirm suitability within the design envelope.

Frequently Asked Questions (FAQ)

Q: Can I use any of these substitute parts interchangeably with the SCHURTER 0034.3987?

A: Yes. All listed parts meet the core electrical and mechanical specifications: 1 A current rating, 250 V AC voltage rating, slow-blow response, 5mm x 20mm package, 35 A breaking capacity, and holder-mount configuration. Physical form factor and electrical performance are equivalent.

Q: What is the difference between SCHURTER series designations (FSD, FST, FSL, FTT, SMD-FST, SMD-FTT)?

A: Series designations indicate internal design variants within SCHURTER's product line. All variants listed maintain identical electrical ratings and package dimensions. Differences in melting I²t values reflect variations in internal element design but do not affect substitution eligibility when core parameters match.

Q: Why do the Littelfuse 239 series parts have different part number suffixes (HXP, MXP, TXP, VXP)?

A: Littelfuse uses suffix designations to differentiate packaging, lead configuration, or internal specifications within the same electrical rating. All four variants (0239001.HXP, 0239001.MXP, 0239001.TXP, 0239001.VXP) are electrically and mechanically equivalent for this application.

Q: Does the melting I²t value affect whether a part can substitute?

A: Melting I²t is a thermal characteristic that influences fuse response behavior under fault conditions. While all listed parts are slow-blow cartridge fuses with identical current and voltage ratings, variations in I²t (ranging from 3.3 to 19.4 in this list) reflect design differences. For applications with specific thermal response requirements, confirm that the substitute part's I²t value is appropriate for the circuit protection scheme.

Q: Are there regional compliance differences I should consider?

A: Yes. The original SCHURTER 0034.3987 carries CSA and UL certifications. SCHURTER active alternatives add CCC, PSE/JET, and VDE approvals, supporting broader regional markets. Littelfuse 239 series parts include CE, CSA, KC, PSE, and UL certifications. Select substitutes based on the compliance requirements of your target market.

Q: Can I use parts with different operating temperature ranges?

A: Operating temperature range defines the ambient conditions under which the fuse maintains rated performance. The original part lists no specified range. SCHURTER alternatives range from -40°C to 85°C or -55°C to 125°C; Littelfuse parts operate from -55°C to 125°C. Confirm that the substitute's temperature range encompasses your application's operating environment.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message