Bel Fuse Inc. 5ET 6.3 Glass Cartridge Fuse 6.3A 250VAC 5x20mm Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. 5ET 6.3 is a 6.3 ampere, 250 volt AC/DC glass cartridge fuse in 5mm x 20mm form factor with slow-blow response characteristics. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for ongoing system maintenance and new designs. The fuse requires a compatible holder for installation and is rated for breaking capacity of 150A at rated voltage with melting I²t of 658.

Key Parameters

Parameter	Value
Current Rating	6.3 A
Voltage Rating (AC)	250 V
Package / Case	5mm x 20mm
Fuse Type	Cartridge, Glass
Response Time	Slow Blow
Mounting Type	Requires Holder
Operating Temperature Range	-55°C ~ 125°C
Breaking Capacity @ Rated Voltage	150A
Melting I²t	658

Substitute Part Grouping Explanation

Substitution of the 5ET 6.3 is determined by strict equivalence in the following parameters:

Current Rating: 6.3 A (exact match required)
Voltage Rating: 250 V AC (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Response Time: Slow Blow (exact match required)
Mounting Type: Requires Holder (exact match required)

Parts are grouped into two categories:

Direct Equivalent: 5ET 6.3-R (Bel Fuse Inc.) — identical series designation with active product status and improved RoHS3 compliance.

Parametric Equivalents: 5ST 6.3-R (Bel Fuse Inc.) — matches all critical electrical and mechanical parameters with lower breaking capacity (63A) and melting I²t (160).

Similar Alternatives: 021806.3HXP, 021806.3MXP, 021806.3TXP, 021806.3VXP (Littelfuse Inc.) and GDC-6.3A (Eaton - Electronics Division) — match all critical parameters with breaking capacity of 63A and varying melting I²t values (198.5 for Littelfuse, 237.6 for Eaton).

Parameter Comparison

Part Number	Manufacturer	Current Rating (A)	Voltage Rating (V AC)	Package	Response Time	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ohms)	Product Status	RoHS Status
5ET 6.3	Bel Fuse Inc.	6.3	250	5x20mm	Slow Blow	150	658	0.009	Obsolete	Non-compliant
5ET 6.3-R	Bel Fuse Inc.	6.3	250	5x20mm	Slow Blow	150	658	0.009	Active	ROHS3 Compliant
5ST 6.3-R	Bel Fuse Inc.	6.3	250	5x20mm	Slow Blow	63	160	0.008	Active	ROHS3 Compliant
021806.3HXP	Littelfuse Inc.	6.3	250	5x20mm	Slow Blow	63	198.5	0.0076	Active	ROHS3 Compliant
021806.3MXP	Littelfuse Inc.	6.3	250	5x20mm	Slow Blow	63	198.5	0.0076	Active	ROHS3 Compliant
021806.3TXP	Littelfuse Inc.	6.3	250	5x20mm	Slow Blow	63	198.5	0.0076	Active	ROHS3 Compliant
021806.3VXP	Littelfuse Inc.	6.3	250	5x20mm	Slow Blow	63	198.5	0.0076	Active	ROHS3 Compliant
GDC-6.3A	Eaton - Electronics Division	6.3	250	5x20mm	Slow Blow	63	237.6	0.0071	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Selection: 5ET 6.3-R (Bel Fuse Inc.) is the direct equivalent with identical electrical and mechanical specifications, active product status, and ROHS3 compliance. This part maintains the original 150A breaking capacity and 658 melting I²t rating.

Secondary Selection: 5ST 6.3-R (Bel Fuse Inc.) provides parametric equivalence with active status and ROHS3 compliance. The reduced breaking capacity (63A) and melting I²t (160) are suitable for applications where the original 150A breaking capacity is not a system requirement.

Alternative Selections: Littelfuse 021806.3HXP, 021806.3MXP, 021806.3TXP, and 021806.3VXP series fuses are functionally equivalent with active product status and ROHS3 compliance. These parts feature breaking capacity of 63A and melting I²t of 198.5. Eaton GDC-6.3A provides similar functionality with breaking capacity of 63A and melting I²t of 237.6.

All substitute parts maintain the required 6.3A current rating, 250V AC voltage rating, 5x20mm package, slow-blow response, and -55°C to 125°C operating temperature range. Selection should account for breaking capacity requirements and system-level fault protection specifications.

Frequently Asked Questions (FAQ)

Q: Can 5ET 6.3-R directly replace the obsolete 5ET 6.3?

A: Yes. The 5ET 6.3-R is the direct equivalent with identical current rating, voltage rating, package dimensions, response time, and breaking capacity. The primary difference is active product status and ROHS3 compliance.

Q: What is the difference between 5ET 6.3-R and 5ST 6.3-R?

A: Both maintain the 6.3A current rating, 250V AC voltage rating, and 5x20mm package. The 5ET 6.3-R retains the original 150A breaking capacity and 658 melting I²t. The 5ST 6.3-R has reduced breaking capacity (63A) and melting I²t (160). Selection depends on system fault protection requirements.

Q: Are Littelfuse 021806.3 series fuses compatible with the original 5ET 6.3 holder?

A: The 021806.3 series maintains the 5x20mm package specification. Physical compatibility with the original holder depends on holder design tolerances. The 021806.3 series has slightly larger diameter (0.205" vs 0.201") and should be evaluated for mechanical fit in the specific holder application.

Q: What is the significance of melting I²t values in fuse selection?

A: Melting I²t determines the thermal energy required to melt the fuse element. The original 5ET 6.3 has melting I²t of 658. Substitute parts with lower melting I²t (160 for 5ST 6.3-R, 198.5 for Littelfuse, 237.6 for Eaton) will respond faster to overcurrent conditions. System protection coordination must account for these differences.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. The 5ET 6.3-R, 5ST 6.3-R, all Littelfuse 021806.3 variants, and Eaton GDC-6.3A are ROHS3 compliant. The original 5ET 6.3 is RoHS non-compliant.

Q: What approval agencies certify these substitute fuses?

A: The 5ET 6.3-R carries CCC, CE, CSA, cURus, SEMKO, and VDE approvals. Littelfuse 021806.3 series carries CCC, CE, CSA, K-MARK, PSE, SEMKO, UL, and VDE approvals. Eaton GDC-6.3A carries cURus, IMQ, and MITI/JET approvals. Application requirements determine which certifications are necessary.

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