Equivalent & Substitute Parts for BK/S506-4-R

Part Overview

The BK/S506-4-R is a 4 A, 250 V AC/DC glass cartridge fuse manufactured by Eaton - Electronics Division. This slow-blow fuse is designed for 5mm x 20mm holder applications and is classified as Active product status. Equivalent and substitute parts are identified to support procurement flexibility, inventory management, and supply chain continuity when the primary part becomes unavailable or when design requirements necessitate alternative manufacturers or series selections.

Key Parameters

Parameter	Value
Current Rating	4 A
Voltage Rating - AC	250 V
Fuse Type	Cartridge, Glass
Response Time	Slow Blow
Package / Case	5mm x 20mm
Mounting Type	Requires Holder
Size / Dimension	0.205" Dia x 0.787" L (5.20mm x 20.00mm)
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict alignment with the following critical parameters:

Primary Substitution Criteria:

Current Rating: 4 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)

Secondary Considerations:

Breaking Capacity @ Rated Voltage: 40 A minimum
Melting I²t: 56 to 410 (acceptable range for slow-blow characteristics)
DC Cold Resistance: 0.0129 to 0.048 Ohms
RoHS3 Compliance: Required
Approval Agencies: Must include at least one common certification (CCC, CSA, VDE, UL, PSE/JET, IMQ, or equivalent)

Parts are grouped as follows:

Parametric Equivalents (Eaton Series): BK/GDC-4A, BK/GMD-4-R, GDC-4A, GMD-4-R meet all primary criteria with identical electrical specifications.

Direct Equivalents (Cross-Manufacturer): 0034.3123 (SCHURTER), 0218004.MXP (Littelfuse), 0034.5623.11 (SCHURTER), 0213004.MXP (Littelfuse) meet all primary criteria with minor variations in secondary parameters.

Similar Parts (Dimensional Tolerance): 5ST 4-R (Bel Fuse) meets all primary criteria with dimensional tolerance of 5.10mm diameter (versus 5.20mm).

Parametric Equivalents (Extended Range): 0034.5049 (SCHURTER) meets all primary criteria with extended melting I²t value of 410.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Series	Current Rating (A)	Voltage Rating - AC (V)	Response Time	Package / Case	Breaking Capacity @ Rated Voltage (A)	Melting I²t	DC Cold Resistance (Ohms)	RoHS Status	Inventory (Pcs)
BK/S506-4-R	Eaton - Electronics Division	S506	4	250	Slow Blow	5mm x 20mm	40	71.8	0.0139	ROHS3 Compliant	742
BK/GDC-4A	Eaton - Electronics Division	GDC	4	250	Slow Blow	5mm x 20mm	40	71.8	0.0139	ROHS3 Compliant	1848
BK/GMD-4-R	Eaton - Electronics Division	GMD	4	250	Slow Blow	5mm x 20mm	200	300	0.048	ROHS3 Compliant	3754
GDC-4A	Eaton - Electronics Division	GDC	4	250	Slow Blow	5mm x 20mm	40	71.8	0.0139	ROHS3 Compliant	1078
GMD-4-R	Eaton - Electronics Division	GMD	4	250	Slow Blow	5mm x 20mm	200	300	0.048	ROHS3 Compliant	911
0034.3123	SCHURTER Inc.	FST 5x20	4	250	Slow Blow	5mm x 20mm	40	68.3	Not Specified	ROHS3 Compliant	58155
0218004.MXP	Littelfuse Inc.	218	4	250	Slow Blow	5mm x 20mm	40	69.1	0.0129	ROHS3 Compliant	22400
5ST 4-R	Bel Fuse Inc.	5ST	4	250	Slow Blow	5mm x 20mm	40	56	0.014	ROHS3 Compliant	31090
0034.5049	SCHURTER Inc.	FTT 5x20	4	250	Slow Blow	5mm x 20mm	35	410	Not Specified	ROHS3 Compliant	3776
0034.5623.11	SCHURTER Inc.	SMD-FST	4	250	Slow Blow	5mm x 20mm	40	68.3	Not Specified	ROHS3 Compliant	1838
0213004.MXP	Littelfuse Inc.	213	4	250	Slow Blow	5mm x 20mm	40	226.505	0.017	ROHS3 Compliant	5552

Engineering Selection Recommendations

Eaton Series Equivalents (BK/GDC-4A, GDC-4A): These parts are direct parametric equivalents to BK/S506-4-R with identical electrical characteristics and breaking capacity. Both maintain Active product status and ROHS3 compliance. Selection is appropriate for direct substitution without design modification. BK/GDC-4A offers higher inventory availability (1848 pcs) compared to the primary part (742 pcs).

Eaton Series with Enhanced Breaking Capacity (BK/GMD-4-R, GMD-4-R): These parts meet all primary substitution criteria but feature enhanced breaking capacity (200 A versus 40 A) and higher melting I²t (300 versus 71.8). These characteristics provide additional protection margin in high-fault-current applications. Selection is appropriate when circuit protection requirements demand higher breaking capacity. GMD-4-R inventory (911 pcs) is lower than primary part.

SCHURTER FST 5x20 Series (0034.3123): This part meets all primary criteria with melting I²t of 68.3 (comparable to primary part at 71.8). Approval agencies include CCC, cURus, PSE/JET, and VDE. Highest inventory availability (58155 pcs) among all substitutes. Operating temperature range specified as -55°C to 125°C. Selection is appropriate for applications requiring extended temperature performance and maximum supply availability.

Littelfuse 218 Series (0218004.MXP): This part meets all primary criteria with melting I²t of 69.1 and DC cold resistance of 0.0129 Ohms (closest match to primary part at 0.0139 Ohms). Approval agencies include CCC, CE, CSA, K-MARK, PSE, SEMKO, UL, and VDE. High inventory availability (22400 pcs). Operating temperature range -55°C to 125°C. Selection is appropriate for applications requiring broad international certification coverage.

Bel Fuse 5ST Series (5ST 4-R): This part meets all primary criteria with dimensional tolerance of 5.10mm diameter (versus 5.20mm standard). Melting I²t of 56 is lower than primary part, indicating faster response characteristics within slow-blow classification. Approval agencies include CCC, CE, CSA, cURus, IMQ, SEMKO, and VDE. High inventory availability (31090 pcs). Selection is appropriate when dimensional tolerance is acceptable and faster response within slow-blow range is acceptable.

SCHURTER FTT 5x20 Series (0034.5049): This part meets all primary criteria with extended melting I²t of 410 (significantly higher than primary part at 71.8). Breaking capacity is 35 A (versus 40 A). Operating temperature range -40°C to 85°C (narrower than other substitutes). Approval agency limited to cURus. Selection is appropriate for applications requiring extended time-delay characteristics and operating within specified temperature range.

SCHURTER SMD-FST Series (0034.5623.11): This part meets all primary criteria with melting I²t of 68.3 (comparable to primary part). Approval agencies include cURus and VDE. Operating temperature range -55°C to 125°C. Inventory availability (1838 pcs) is comparable to primary part. Selection is appropriate for applications requiring extended temperature performance and European certification focus.

Littelfuse 213 Series (0213004.MXP): This part meets all primary criteria with melting I²t of 226.505 (higher than primary part, indicating extended time-delay). DC cold resistance of 0.017 Ohms is within acceptable range. Approval agencies include BSI, CCC, CE, CSA, PSE, SEMKO, UR, and VDE. Operating temperature range -55°C to 125°C. Selection is appropriate for applications requiring extended time-delay characteristics and broad international certification.

Frequently Asked Questions (FAQ)

Q: Can BK/S506-4-R be directly replaced with BK/GDC-4A?

A: Yes. BK/GDC-4A is a parametric equivalent with identical current rating (4 A), voltage rating (250 V AC), response time (Slow Blow), package (5mm x 20mm), breaking capacity (40 A), and melting I²t (71.8). Both are Eaton products with Active status and ROHS3 compliance. Direct substitution is supported without design modification.

Q: What is the difference between BK/GMD-4-R and BK/S506-4-R?

A: Both parts share identical current rating (4 A), voltage rating (250 V AC), response time (Slow Blow), and package (5mm x 20mm). The GMD series features enhanced breaking capacity (200 A versus 40 A) and higher melting I²t (300 versus 71.8). The GMD series is suitable for applications requiring higher fault-current protection. DC cold resistance differs (0.048 Ohms versus 0.0139 Ohms).

Q: Are cross-manufacturer substitutes (SCHURTER, Littelfuse, Bel Fuse) compatible with the same holder as BK/S506-4-R?

A: Yes. All substitute parts listed maintain the 5mm x 20mm package specification and Requires Holder mounting type. Physical compatibility with standard 5mm x 20mm fuse holders is confirmed. Electrical compatibility is verified through matching current rating (4 A), voltage rating (250 V AC), and response time (Slow Blow).

Q: Which substitute offers the highest inventory availability?

A: SCHURTER 0034.3123 (FST 5x20 series) offers the highest inventory availability at 58155 pcs. This part meets all primary substitution criteria and includes approval agencies CCC, cURus, PSE/JET, and VDE. Operating temperature range is -55°C to 125°C.

Q: What is the significance of melting I²t variation among substitutes?

A: Melting I²t determines the thermal energy required to melt the fuse element and is a key characteristic of slow-blow response. Primary part BK/S506-4-R has melting I²t of 71.8. Substitutes range from 56 (Bel Fuse 5ST 4-R, faster response) to 410 (SCHURTER FTT 5x20, extended time-delay). Selection should match application requirements for circuit protection timing. Parts with melting I²t between 56 and 226.505 are suitable for standard slow-blow applications.

Q: Are all substitutes ROHS3 compliant?

A: Yes. All substitute parts listed are ROHS3 compliant, matching the primary part BK/S506-4-R. This ensures compliance with environmental and hazardous substance restrictions across all listed alternatives.

Q: Which substitutes have the broadest international certification coverage?

A: Littelfuse 0218004.MXP (218 series) includes approval agencies CCC, CE, CSA, K-MARK, PSE, SEMKO, UL, and VDE. Littelfuse 0213004.MXP (213 series) includes BSI, CCC, CE, CSA, PSE, SEMKO, UR, and VDE. Both provide comprehensive international certification suitable for global applications.

Q: Can 5ST 4-R (Bel Fuse) be used if the holder has tight dimensional tolerances?

A: 5ST 4-R has a diameter of 5.10mm versus the standard 5.20mm. If the fuse holder has tight dimensional tolerances, verification of fit is required before substitution. All other listed substitutes maintain the standard 5.20mm diameter specification.

Q: What is the operating temperature range for substitutes?

A: Most substitutes specify operating temperature range of -55°C to 125°C (SCHURTER FST 5x20, Littelfuse 218 and 213 series, Bel Fuse 5ST, SCHURTER SMD-FST). SCHURTER FTT 5x20 specifies narrower range of -40°C to 85°C. Primary part BK/S506-4-R does not specify operating temperature. Selection should verify compatibility with application temperature requirements.

Q: Are there differences in DC cold resistance among substitutes?

A: Yes. DC cold resistance varies: BK/S506-4-R (0.0139 Ohms), Littelfuse 0218004.MXP (0.0129 Ohms), Littelfuse 0213004.MXP (0.017 Ohms), Bel Fuse 5ST 4-R (0.014 Ohms), BK/GMD-4-R (0.048 Ohms). Lower resistance values indicate lower voltage drop across the fuse element. For most applications, these variations are negligible. Applications with strict voltage drop requirements should verify compatibility.

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