SCHURTER 0034.3979 Equivalent & Substitute Parts

Part Overview

The SCHURTER 0034.3979 is a 300 mA, 250 V AC/DC glass cartridge fuse with 5mm x 20mm dimensions and slow-blow response characteristics. This part is classified as obsolete, necessitating identification of active equivalent alternatives for ongoing circuit protection applications. Substitute parts must maintain identical electrical ratings, mechanical form factor, and approval certifications to ensure direct functional replacement without circuit redesign.

Key Parameters

Parameter	Value
Current Rating	300 mA
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Slow Blow
Breaking Capacity @ Rated Voltage	35 A
Mounting Type	Requires Holder
RoHS Status	ROHS3 Compliant
Approval Agencies	CSA, UL

Substitute Part Grouping Explanation

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

Current Rating: 300 mA (exact match required)
Voltage Rating: 250 V AC (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Response Time: Slow Blow (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Mounting Type: Requires Holder (exact match required)

All identified substitute parts meet these criteria. Variations in melting I²t, DC cold resistance, breaking capacity, and operating temperature ranges do not preclude substitution when all primary electrical and mechanical parameters align.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Current Rating (Amps)	Voltage Rating - AC	Response Time	Package / Case	Breaking Capacity @ Rated Voltage	Melting I²t	Product Status	Approval Agency	RoHS Status
0034.3979	SCHURTER Inc.	300 mA	250 V	Slow Blow	5mm x 20mm	35 A	0.621	Obsolete	CSA, UL	ROHS3 Compliant
0239.300MXP	Littelfuse Inc.	300 mA	250 V	Slow Blow	5mm x 20mm	35 A	0.615	Active	CE, CSA, KC, UL	ROHS3 Compliant
0239.300TXP	Littelfuse	300 mA	250 V	Slow Blow	5mm x 20mm	35 A	0.615	Active	CE, CSA, KC, UL	ROHS3 Compliant
0239.300VXP	Littelfuse Inc.	300 mA	250 V	Slow Blow	5mm x 20mm	35 A	0.615	Active	CE, CSA, KC, UL	ROHS3 Compliant
0239.300HXP	Littelfuse Inc.	300 mA	250 V	Slow Blow	5mm x 20mm	35 A	0.615	Active	CE, CSA, KC, UL	ROHS3 Compliant
BK/GMD-300-R	Eaton - Electronics Division	300 mA	250 V	Slow Blow	5mm x 20mm	35 A	0.65	Active	CSA, UL	ROHS3 Compliant
BK1/GMD-300-R	Eaton - Electronics Division	300 mA	250 V	Slow Blow	5mm x 20mm	35 A	0.65	Active	CSA, UL	ROHS3 Compliant
GMD-300-R	Eaton - Electronics Division	300 mA	250 V	Slow Blow	5mm x 20mm	35 A	0.65	Active	CSA, UL	ROHS3 Compliant
TSC-300MA	OptiFuse	300 mA	250 V	Slow Blow	5mm x 20mm	100 A	0.4817	Active	cULus, UL 248	ROHS3 Compliant

Engineering Selection Recommendations

All substitute parts listed are active products with current manufacturing status, eliminating obsolescence risk. Selection among equivalents should prioritize parts with certifications matching the original application requirements:

Littelfuse 239 series (0239.300MXP, 0239.300TXP, 0239.300VXP, 0239.300HXP) provide direct parametric equivalence with extended approval coverage (CE, CSA, KC, UL) and defined operating temperature ranges (-55°C to 125°C). These parts are suitable for applications requiring broader international compliance.

Eaton GMD series (BK/GMD-300-R, BK1/GMD-300-R, GMD-300-R) maintain CSA and UL certifications matching the original part and offer higher inventory availability. DC cold resistance specifications (3.215 Ohms) differ from Littelfuse variants (2.3 Ohms), which may be relevant for low-voltage circuit applications.

OptiFuse TSC-300MA provides the highest breaking capacity (100 A) and lowest melting I²t (0.4817), offering enhanced protection margins in high-fault-current environments. UL 248 certification confirms compliance with fuse standards.

Frequently Asked Questions (FAQ)

Q: Can I substitute the SCHURTER 0034.3979 with any of the listed parts?

A: Yes. All listed parts meet the mandatory substitution criteria: 300 mA current rating, 250 V AC voltage rating, 5mm x 20mm package, slow-blow response, and cartridge glass fuse type. Direct mechanical and electrical compatibility is confirmed.

Q: What is the difference between Littelfuse and Eaton fuses in this list?

A: Littelfuse 239 series parts feature lower DC cold resistance (2.3 Ohms) and extended operating temperature range (-55°C to 125°C). Eaton GMD series parts have higher DC cold resistance (3.215 Ohms) and broader CSA/UL certification. Both are functionally equivalent for the specified electrical parameters.

Q: Why does the OptiFuse TSC-300MA have a higher breaking capacity (100 A vs. 35 A)?

A: Breaking capacity indicates the maximum fault current the fuse can safely interrupt. The TSC-300MA's higher breaking capacity (100 A) provides enhanced protection capability in circuits with higher available fault currents. This does not affect substitution eligibility when all primary electrical ratings match.

Q: Are there any temperature operating range considerations for substitution?

A: The original SCHURTER part does not specify an operating temperature range. Littelfuse and OptiFuse parts define -55°C to 125°C operating ranges. Eaton parts do not specify operating temperature. For applications with temperature extremes, Littelfuse or OptiFuse variants are recommended.

Q: Do all substitute parts require the same holder as the original SCHURTER fuse?

A: Yes. All substitute parts are 5mm x 20mm cartridge fuses requiring a holder. Existing fuse holders are mechanically compatible with all listed alternatives.

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