Equivalent & Substitute Parts for 02191.25MXAP

Part Overview

The Littelfuse 02191.25MXAP is a 1.25 A, 250 V AC glass cartridge fuse with 5mm x 20mm dimensions, designed for applications requiring slow-blow response characteristics. This fuse is classified as Active product status and is ROHS3 compliant. Alternative equivalent parts may be required due to inventory availability, specific approval agency requirements, or application-specific performance parameters such as breaking capacity or melting I²t characteristics.

Key Parameters

Parameter	Value
Current Rating	1.25 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
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict alignment with the following core parameters: current rating (1.25 A), voltage rating (250 V AC), package dimensions (5mm x 20mm), fuse type (cartridge glass), response time (slow blow), and mounting configuration (requires holder). Parts are grouped into three categories based on substitution relationship type:

Parametric Equivalents share all core electrical and mechanical parameters with the main part but may differ in breaking capacity, melting I²t, approval agencies, or DC cold resistance. These parts are direct functional replacements within the same application envelope.

Direct Manufacturer Alternatives meet core parameters but introduce variations in response time classification or DC voltage rating, requiring application-level verification.

Manufacturer Recommended Alternatives are approved substitutes from alternative manufacturers that maintain core parameter alignment while offering different performance characteristics in breaking capacity or melting I²t.

Parameter Comparison

Part Number	Manufacturer	Series	Current (A)	Voltage AC (V)	Response Time	Package	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Inventory (Pcs)
02191.25MXAP	Littelfuse Inc.	219XA	1.25	250	Slow Blow	5x20mm	150	27.15	0.0817	1587
02131.25MXP	Littelfuse Inc.	213	1.25	250	Slow Blow	5x20mm	35	27.15	0.0817	3448
02181.25HXP	Littelfuse Inc.	218	1.25	250	Slow Blow	5x20mm	35	12.65	0.0446	5238
02181.25MXP	Littelfuse Inc.	218	1.25	250	Slow Blow	5x20mm	35	12.65	0.0446	4296
02181.25TXP	Littelfuse Inc.	218	1.25	250	Slow Blow	5x20mm	35	12.65	0.0446	1155
02391.25HXP	Littelfuse Inc.	239	1.25	250	Slow Blow	5x20mm	100	19.525	0.198	881
0034.2517	SCHURTER Inc.	FSM 5x20	1.25	250	Medium Blow	5x20mm	80	5.47	—	1618
5ET 1.25-R	Bel Fuse Inc.	5ET	1.25	250	Slow Blow	5x20mm	150	42	0.08	11329
5TT 1.25-R	Bel Fuse Inc.	5TT	1.25	250	Slow Blow	5x20mm	100	13.1	0.206	1862
0034.3118	SCHURTER Inc.	FST 5x20	1.25	250	Slow Blow	5x20mm	35	5.5	—	13782
0034.5618.11	SCHURTER Inc.	SMD-FST	1.25	250	Slow Blow	5x20mm	35	5.5	—	1181

Engineering Selection Recommendations

Littelfuse Series 218 (02181.25HXP, 02181.25MXP, 02181.25TXP) are parametric equivalents with identical current, voltage, and response characteristics. These parts feature reduced melting I²t (12.65 vs. 27.15) and lower DC cold resistance (0.0446 Ω vs. 0.0817 Ω), making them suitable for applications where faster thermal response is acceptable. All three variants carry CCC, CE, CSA, PSE, SEMKO, UL, and VDE certifications, with 02181.25TXP additionally certified by KC.

Littelfuse Series 213 (02131.25MXP) maintains identical melting I²t and DC cold resistance to the main part but reduces breaking capacity to 35 A. This part is suitable for lower-fault-current applications and carries BSI, CCC, CE, CSA, PSE, SEMKO, UR, and VDE certifications.

Littelfuse Series 239 (02391.25HXP) offers intermediate breaking capacity (100 A) with melting I²t of 19.525. Certification coverage is limited to CE, CSA, KC, PSE, and UL, with no CCC or VDE approval.

Bel Fuse 5ET 1.25-R matches the main part's breaking capacity (150 A) and response time, with higher melting I²t (42 vs. 27.15). Certifications include CCC, CE, CSA, cURus, SEMKO, and VDE. Dimensions are 5.10mm x 20.00mm (0.1mm diameter variance).

Bel Fuse 5TT 1.25-R provides 100 A breaking capacity with lower melting I²t (13.1). Certifications are limited to CE, CSA, cULus, and PSE. Dimensions are 5.10mm x 20.00mm.

SCHURTER FST 5x20 (0034.3118) and SCHURTER SMD-FST (0034.5618.11) both feature 35 A breaking capacity and low melting I²t (5.5). These parts carry CCC, cURus, PSE/JET, and VDE certifications (FST 5x20) or cURus and VDE only (SMD-FST).

SCHURTER FSM 5x20 (0034.2517) is classified as medium-blow response, differing from the slow-blow specification of the main part. This part carries no listed approval agencies and operates within -40°C to 85°C temperature range, narrower than the main part's -55°C to 125°C range.

Frequently Asked Questions (FAQ)

Q: Can I use a part with different breaking capacity as a direct substitute?

A: Breaking capacity determines the fuse's ability to safely interrupt fault currents. Parts with lower breaking capacity (35 A vs. 150 A) are suitable only for applications with correspondingly lower available fault current. Parts with higher breaking capacity provide additional safety margin but do not compromise circuit protection at rated current.

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

A: Melting I²t defines the thermal energy required to melt the fuse element. Lower melting I²t values result in faster response to overcurrent conditions. The main part (27.15) and Series 213 (27.15) are identical; Series 218 parts (12.65) respond faster; Bel Fuse 5ET (42) responds slower. Selection depends on circuit protection requirements and component thermal tolerance.

Q: Are SCHURTER parts with different response time classifications compatible?

A: The SCHURTER FSM 5x20 (0034.2517) is classified as medium-blow, while the main part and most alternatives are slow-blow. Response time classification affects overcurrent protection timing. Medium-blow fuses interrupt faster than slow-blow fuses at the same current level. Substitution requires application-level verification of circuit protection requirements.

Q: What approval agencies are critical for my application?

A: Approval agency certifications vary across substitute parts. The main part carries CCC, CE, CSA, PSE, SEMKO, UL, and VDE certifications. If your application requires specific regional certifications (e.g., CCC for China, UL for North America), verify that the substitute part carries equivalent certifications before selection.

Q: Do dimensional variations between manufacturers affect compatibility?

A: The main part and most Littelfuse alternatives are 5.20mm diameter x 20.00mm length. Bel Fuse parts are 5.10mm diameter x 20.00mm length (0.1mm variance). Both dimensions are within standard 5x20mm cartridge fuse specifications and are compatible with standard fuse holders. SCHURTER parts maintain 5.20mm x 20.00mm dimensions.

Q: Can I substitute a part with lower DC cold resistance?

A: DC cold resistance affects voltage drop across the fuse during normal operation. Lower resistance (0.0446 Ω in Series 218 vs. 0.0817 Ω in the main part) reduces power dissipation and heat generation. This substitution is generally favorable for thermal performance but should be verified if the circuit design accounts for specific resistance values.

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