PFRX.135.3 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The PFRX.135.3 is a polymeric PTC resettable fuse manufactured by SCHURTER Inc., rated for 60V at 1.35A hold current with through-hole radial disc packaging. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing design support and procurement continuity. The PFRX series has been superseded by active production alternatives that maintain electrical compatibility while offering improved availability and active manufacturer support.

Key Parameters

Parameter	Value
Voltage - Max	60V
Current - Hold (Ih) (Max)	1.35 A
Current - Trip (It)	2.7 A
Current - Max	40 A
Time to Trip	9.6 s
Resistance - Initial (Ri) (Min)	120 mOhms
Resistance - Post Trip (R1) (Max)	300 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Lead Spacing	0.201" (5.10mm)
Type	Polymeric

Substitute Part Grouping Explanation

Substitution eligibility for the PFRX.135.3 is determined by the following critical parameters:

Electrical Compatibility Requirements:

Current - Hold (Ih) must equal 1.35 A
Current - Trip (It) must equal 2.7 A
Resistance - Initial (Ri) must equal 120 mOhms minimum
Resistance - Post Trip (R1) must not exceed 300 mOhms
Time to Trip must equal 9.6 s
Operating Temperature range must encompass -40°C ~ 85°C

Mechanical Compatibility Requirements:

Mounting Type must be Through Hole
Package / Case must be Radial, Disc
Lead Spacing must be 0.201" (5.10mm) or equivalent

Voltage Consideration: Substitute parts rated at 72V maximum voltage are acceptable for applications designed for 60V operation, as higher voltage ratings provide backward compatibility in lower-voltage circuits. The PFRY.135 and RXEF135-AP both meet this criterion.

Parameter Comparison

Parameter	PFRX.135.3 (Main)	PFRY.135 (Substitute)	RXEF135-AP (Substitute)
Manufacturer	SCHURTER Inc.	SCHURTER Inc.	Littelfuse Inc.
Product Status	Obsolete	Active	Active
Voltage - Max	60V	72V	72V
Current - Hold (Ih) (Max)	1.35 A	1.35 A	1.35 A
Current - Trip (It)	2.7 A	2.7 A	2.7 A
Current - Max	40 A	40 A	40 A
Time to Trip	9.6 s	9.6 s	9.6 s
Resistance - Initial (Ri) (Min)	120 mOhms	120 mOhms	120 mOhms
Resistance - Post Trip (R1) (Max)	300 mOhms	300 mOhms	300 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	Radial, Disc	Radial, Disc	Radial, Disc
Lead Spacing	0.201" (5.10mm)	0.201" (5.10mm)	0.200" (5.08mm)
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	CSA, TUV, UL	cURus, TUV	CQC, CSA, TUV, UL

Engineering Selection Recommendations

Both PFRY.135 and RXEF135-AP are qualified substitutes for the obsolete PFRX.135.3 based on electrical and mechanical parameter equivalence.

PFRY.135 (SCHURTER Inc.):

Maintains manufacturer continuity with the original PFRX series
Active product status ensures long-term availability
Holds cURus and TUV certifications
Identical electrical specifications and lead spacing
Suitable for designs requiring SCHURTER component consistency

RXEF135-AP (Littelfuse Inc.):

Broadest certification coverage: CQC, CSA, TUV, UL
Active product status with higher inventory availability (2021 pcs)
PolySwitch® series designation indicates established market presence
Lead spacing tolerance of 0.200" (5.08mm) is within acceptable mechanical compatibility
Recommended for applications requiring maximum regulatory compliance coverage

Both substitutes are ROHS3 compliant and REACH unaffected, meeting modern environmental standards.

Frequently Asked Questions (FAQ)

Q: Can PFRY.135 or RXEF135-AP be used as direct replacements for PFRX.135.3?

A: Yes. Both substitute parts maintain identical hold current (1.35A), trip current (2.7A), resistance characteristics, and time-to-trip specifications. The higher voltage ratings (72V vs. 60V) provide backward compatibility for 60V circuit applications. Through-hole radial disc packaging and lead spacing are mechanically compatible.

Q: Why do the substitute parts have higher voltage ratings (72V) than the original (60V)?

A: Higher voltage-rated components are acceptable substitutes in lower-voltage applications. A 72V-rated fuse will function correctly in a 60V circuit without performance degradation. This represents an upgrade in voltage margin rather than a limitation.

Q: What is the difference between PFRY.135 and RXEF135-AP?

A: Both parts are electrically equivalent. The primary differences are manufacturer (SCHURTER vs. Littelfuse), certification bodies (PFRY.135 holds cURus/TUV; RXEF135-AP holds CQC/CSA/TUV/UL), and packaging format (Bulk vs. Cut Tape). RXEF135-AP offers broader regulatory approvals and higher inventory availability.

Q: Are there any mechanical compatibility concerns with the lead spacing difference?

A: The lead spacing difference between PFRY.135 (0.201" / 5.10mm) and RXEF135-AP (0.200" / 5.08mm) is 0.02mm, which is within standard PCB tolerance for through-hole component placement and does not present compatibility issues.

Q: Which substitute should be selected for new designs?

A: Selection depends on design requirements. Choose PFRY.135 for manufacturer continuity with SCHURTER components. Choose RXEF135-AP for maximum regulatory certification coverage and established market availability through multiple distribution channels.

Q: Are both substitutes RoHS compliant?

A: Yes. Both PFRY.135 and RXEF135-AP are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory requirements.

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