Equivalent & Substitute Parts for BK/MDL-3 Glass Cartridge Fuse

Part Overview

The BK/MDL-3 is a 3 A, 250 V AC/DC slow-blow glass cartridge fuse manufactured by Eaton - Electronics Division. This fuse is designed for use in 3AB and 3AG holders with dimensions of 0.250" diameter by 1.250" length (6.35 mm × 31.75 mm). The part is classified as obsolete, necessitating identification of active equivalent and substitute components that maintain electrical and mechanical compatibility. Equivalent parts are available from both Eaton and Littelfuse manufacturers, with improved compliance profiles and active product status.

Key Parameters

Parameter	Value
Current Rating	3 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Response Time	Slow Blow
Package / Case	3AB, 3AG, 1/4" × 1-1/4"
Size / Dimension	0.250" Dia × 1.250" L (6.35 mm × 31.75 mm)
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	100 A (standard); 35 A (MDQ-3 variant)
Melting I²t	67.5 (Eaton); 200 (Littelfuse)

Substitute Part Grouping Explanation

Substitution of the BK/MDL-3 is determined by strict equivalence across the following electrical and mechanical parameters:

Critical Compatibility Parameters:

Current Rating: 3 A (exact match required)
Voltage Rating: 250 V AC (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Response Time: Slow Blow (exact match required)
Package / Case: 3AB, 3AG, 1/4" × 1-1/4" (exact match required)
Physical Dimensions: 0.250" Dia × 1.250" L (exact match required)

All substitute parts listed maintain these critical parameters. Variations in secondary characteristics such as DC cold resistance, melting I²t, breaking capacity, RoHS compliance status, and approval agencies do not preclude substitution when the above parameters are identical.

Eaton MDL series parts (BK/MDL-3-R, MDL-3-R, BK/MDL-3RX-R) and Eaton MDQ series parts (BK/MDQ-3, MDQ-3) are direct parametric equivalents. Littelfuse 313 series parts (0313003.HXP, 0313003.MXP, 0313003.VXP, 0313003.HXIDP, 0313003.VXIDP) are parametric equivalents from an alternative manufacturer.

Parameter Comparison

Part Number	Manufacturer	Current (A)	Voltage (V AC)	Response Time	Package	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status	RoHS Status
BK/MDL-3	Eaton	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	67.5	0.067	Obsolete	Non-compliant
BK/MDL-3-R	Eaton	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	67.5	0.057	Active	ROHS3 Compliant
MDL-3-R	Eaton	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	67.5	0.057	Active	RoHS Compliant
BK/MDL-3RX-R	Eaton	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	67.5	0.057	Active	RoHS Compliant
BK/MDQ-3	Eaton	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	Not specified	0.05715	Active	Non-compliant
MDQ-3	Eaton	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	35	Not specified	0.05715	Active	Not specified
0313003.HXP	Littelfuse	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	200	0.0593	Active	ROHS3 Compliant
0313003.MXP	Littelfuse	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	200	0.0593	Active	ROHS3 Compliant
0313003.VXP	Littelfuse	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	200	0.0593	Active	ROHS3 Compliant
0313003.HXIDP	Littelfuse	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	200	0.0593	Active	ROHS3 Compliant
0313003.VXIDP	Littelfuse	3	250	Slow Blow	3AB, 3AG, 1/4" × 1-1/4"	100	200	0.0593	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation - Eaton Manufacturer:

BK/MDL-3-R or MDL-3-R are the preferred direct substitutes for BK/MDL-3. Both parts are manufactured by Eaton - Electronics Division and maintain identical electrical and mechanical specifications. These parts carry active product status and RoHS compliance certification, addressing the obsolescence of the original part. BK/MDL-3-R includes ROHS3 compliance with CE certification, while MDL-3-R provides RoHS compliance. Both are approved by CSA and UL agencies.

Alternative Recommendation - Eaton MDQ Series:

BK/MDL-3RX-R provides an active alternative within the Eaton product line with identical electrical parameters and RoHS compliance. MDQ-3 and BK/MDQ-3 are active Eaton alternatives; however, MDQ-3 specifies a breaking capacity of 35 A compared to the 100 A rating of other equivalents.

Cross-Manufacturer Alternative - Littelfuse:

The Littelfuse 313 series parts (0313003.HXP, 0313003.MXP, 0313003.VXP, 0313003.HXIDP, 0313003.VXIDP) are parametric equivalents meeting all critical electrical and mechanical requirements. These parts are active, ROHS3 compliant, and approved by CE, CSA, UL, and additional agencies (K-MARK, PSE, KC). Littelfuse parts specify an operating temperature range of -55°C to 125°C and a melting I²t of 200, compared to the Eaton specification of 67.5.

Compliance Considerations:

For applications requiring RoHS3 compliance and CE certification, BK/MDL-3-R or Littelfuse 313 series parts are appropriate selections. For applications with no specific compliance requirements, MDL-3-R or BK/MDL-3RX-R provide equivalent functionality with active product status.

Frequently Asked Questions (FAQ)

Q: Can BK/MDL-3-R directly replace BK/MDL-3 in existing applications?

A: Yes. BK/MDL-3-R maintains identical electrical ratings (3 A, 250 V AC), response time (slow blow), and physical dimensions (0.250" Dia × 1.250" L). Both parts require the same 3AB or 3AG holder. The primary difference is product status (active versus obsolete) and improved RoHS compliance.

Q: What is the difference between Eaton MDL and MDQ series fuses?

A: Both series meet the critical electrical and mechanical parameters for substitution. The MDQ series includes variants with different breaking capacities. MDQ-3 specifies 35 A breaking capacity, while MDL variants specify 100 A. Selection depends on application requirements for breaking capacity.

Q: Are Littelfuse 313 series parts fully compatible with Eaton MDL-3?

A: Yes, from an electrical and mechanical standpoint. All Littelfuse 313 series parts listed (0313003.HXP, 0313003.MXP, 0313003.VXP, 0313003.HXIDP, 0313003.VXIDP) maintain the required 3 A, 250 V AC rating, slow-blow response, and 3AB/3AG package compatibility. Differences in melting I²t (200 versus 67.5) and operating temperature range (-55°C to 125°C) reflect design variations between manufacturers but do not affect substitution eligibility based on the specified parameters.

Q: What does RoHS compliance status indicate for fuse selection?

A: RoHS compliance indicates the part meets restrictions on hazardous substances. BK/MDL-3 is RoHS non-compliant. BK/MDL-3-R and Littelfuse parts are ROHS3 compliant. For applications subject to RoHS regulations or customer requirements, ROHS3 compliant parts are necessary.

Q: Can I use MDQ-3 as a substitute if breaking capacity is not a critical parameter?

A: Yes. MDQ-3 maintains all critical electrical and mechanical parameters (3 A, 250 V AC, slow blow, 3AB/3AG package, 0.250" Dia × 1.250" L). The reduced breaking capacity of 35 A versus 100 A is a secondary characteristic. Selection depends on whether the application circuit design accommodates this specification difference.

Q: What approval agencies certify these substitute parts?

A: BK/MDL-3-R carries CE, CSA, and UL approvals. MDL-3-R carries CSA and UL approvals. Littelfuse 313 series parts carry CE, CSA, UL, K-MARK, and PSE approvals, with some variants including KC certification. Selection should align with application regulatory requirements.

Q: Are there inventory considerations when selecting a substitute?

A: Inventory levels vary across part numbers. 0313003.HXP (Littelfuse) has the highest inventory at 3,458 pieces. BK/MDL-3-R has 1,879 pieces. MDL-3-R has 877 pieces. Availability should be confirmed for production requirements.

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