GMC-125-R Equivalent & Substitute Parts Reference

Part Overview

The GMC-125-R is a 125 mA, 250 V AC/DC glass cartridge fuse manufactured by Eaton - Electronics Division. This medium-blow fuse is designed for applications requiring a 5mm x 20mm form factor with holder mounting. The part is active in production with 990 pieces in current inventory. Equivalent and substitute parts are identified for applications where alternative manufacturers' components meet the specified electrical and mechanical parameters, or where design requirements necessitate different response characteristics or breaking capacities.

Key Parameters

Parameter	Value
Current Rating	125 mA
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Medium Blow
Breaking Capacity @ Rated Voltage	35A
Mounting Type	Requires Holder
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the GMC-125-R are classified based on alignment with core electrical and mechanical parameters: current rating (125 mA), voltage rating (250 V AC), package dimensions (5mm x 20mm), fuse type (cartridge glass), and mounting requirement (holder-based). Substitution categories are defined as follows:

Direct Manufacturer Equivalent: Parts sharing identical electrical specifications, response time, and breaking capacity from the same manufacturer series.

Similar Manufacturer Parts: Components from alternative manufacturers meeting current, voltage, and package specifications but with different response time characteristics (slow blow vs. medium blow) or breaking capacity ratings.

Parametric Equivalents: Parts matching core electrical parameters and package form factor with variations in response time, breaking capacity, or thermal operating range.

The following parameters determine substitution validity:

Current Rating: 125 mA (fixed requirement)
Voltage Rating: 250 V AC (fixed requirement)
Package Dimensions: 5mm x 20mm (fixed requirement)
Fuse Type: Cartridge, Glass (fixed requirement)
Mounting: Holder-based (fixed requirement)

Parameter Comparison

Part Number	Manufacturer	Current Rating	Voltage Rating (AC)	Response Time	Package	Breaking Capacity @ Rated Voltage	Melting I²t	DC Cold Resistance (Ohms)	Approval Agency	RoHS Status
GMC-125-R	Eaton - Electronics Division	125 mA	250 V	Medium Blow	5mm x 20mm	35A	0.014	3.4	CSA, KC-MARK, UL	ROHS3 Compliant
BK/GMC-125-R	Eaton - Electronics Division	125 mA	250 V	Medium Blow	5mm x 20mm	35A	0.014	3.4	CSA, KC-MARK, UL	ROHS3 Compliant
0218.125HXP	Littelfuse Inc.	125 mA	250 V	Slow Blow	5mm x 20mm	35A	0.1465	4.2	CCC, CE, CSA, K-MARK, SEMKO, UL, VDE	ROHS3 Compliant
0218.125MXP	Littelfuse Inc.	125 mA	250 V	Slow Blow	5mm x 20mm	35A	0.1465	4.2	CCC, CE, CSA, K-MARK, SEMKO, UL, VDE	ROHS3 Compliant
MSC-125MA	OptiFuse	125 mA	250 V	Medium Blow	5mm x 20mm	100A	0.0253	Not Specified	cULus, UL 248	ROHS3 Compliant

Engineering Selection Recommendations

BK/GMC-125-R (Eaton - Electronics Division): This part is a direct equivalent to GMC-125-R with identical electrical specifications, response time, and breaking capacity. Both parts are manufactured by Eaton and share the same series designation (GMC). Selection of BK/GMC-125-R is appropriate for applications requiring continuity with the original specification. Approvals include CSA, KC-MARK, and UL.

0218.125HXP and 0218.125MXP (Littelfuse Inc.): These parts match the current rating, voltage rating, and package dimensions of GMC-125-R. Both are slow-blow fuses with higher melting I²t values (0.1465 vs. 0.014) and increased DC cold resistance (4.2 Ohms vs. 3.4 Ohms). Selection of these parts is appropriate for applications where slow-blow response is required instead of medium-blow response. Approvals include CCC, CE, CSA, K-MARK, SEMKO, UL, and VDE. Operating temperature range is specified as -55°C to 125°C.

MSC-125MA (OptiFuse): This part matches the current rating, voltage rating, package dimensions, and response time (medium blow) of GMC-125-R. The breaking capacity is rated at 100A, which exceeds the 35A rating of GMC-125-R. Melting I²t is 0.0253, which is higher than GMC-125-R. Selection of MSC-125MA is appropriate for applications requiring higher breaking capacity. Approvals include cULus and UL 248. Operating temperature range is specified as -55°C to 125°C.

Frequently Asked Questions (FAQ)

Q: Can BK/GMC-125-R be used as a direct replacement for GMC-125-R?

A: Yes. BK/GMC-125-R is manufactured by Eaton - Electronics Division and shares identical electrical specifications, response time (medium blow), breaking capacity (35A), and package dimensions (5mm x 20mm) with GMC-125-R. Both parts require holder mounting and are ROHS3 compliant.

Q: What is the difference between medium-blow and slow-blow response times?

A: Response time refers to the fuse element's thermal response to overcurrent conditions. Medium-blow fuses (GMC-125-R, MSC-125MA) operate with standard thermal characteristics. Slow-blow fuses (0218.125HXP, 0218.125MXP) have higher melting I²t values and tolerate temporary inrush currents before opening. Selection depends on application requirements for transient current handling.

Q: Can Littelfuse 0218.125HXP or 0218.125MXP replace GMC-125-R in all applications?

A: These parts are mechanically and electrically compatible in terms of current rating, voltage rating, and package dimensions. However, they feature slow-blow response instead of medium-blow response. Substitution is appropriate only for applications where slow-blow characteristics are acceptable or required. The higher melting I²t (0.1465 vs. 0.014) and increased DC cold resistance (4.2 Ohms vs. 3.4 Ohms) must be evaluated against application requirements.

Q: What is the advantage of MSC-125MA over GMC-125-R?

A: MSC-125MA provides a higher breaking capacity rating of 100A compared to GMC-125-R's 35A rating. Both parts share medium-blow response time and identical current/voltage/package specifications. MSC-125MA is appropriate for applications requiring higher fault current interruption capability. OptiFuse approvals include cULus and UL 248.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. GMC-125-R, BK/GMC-125-R, 0218.125HXP, 0218.125MXP, and MSC-125MA are all ROHS3 compliant.

Q: What certifications should I verify for my specific application?

A: GMC-125-R carries CSA, KC-MARK, and UL approvals. Littelfuse parts (0218.125HXP, 0218.125MXP) carry CCC, CE, CSA, K-MARK, SEMKO, UL, and VDE approvals. MSC-125MA carries cULus and UL 248 approvals. Verify that the selected part's certification list includes all required approvals for your application's geographic and regulatory requirements.

Q: Can these fuses be used without a holder?

A: No. All listed parts require holder mounting. The 5mm x 20mm cartridge fuse form factor is designed for use with compatible fuse holders. Direct contact installation is not supported.

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