Equivalent & Substitute Parts for Cornell Dubilier Electronics 21FD3740

Part Overview

The Cornell Dubilier Electronics 21FD3740 is a 40 µF film capacitor rated for 370V AC operation with polypropylene metallized dielectric construction. This radial, can-style component is designed for chassis mount applications requiring a holder or bracket. The part is currently active in production with 992 units in stock inventory.

Film capacitors of this specification are essential in motor run and power factor correction applications where stable capacitance, low dissipation factor, and reliable performance across extended temperature ranges are required. Equivalent and substitute parts may be necessary due to supply chain considerations, inventory availability, or application-specific performance requirements.

Substiute Parts

21FD3740

Cornell Dubilier Electronics (CDE)In Stock: 102821FD3740 Datasheet

Current PartRFQ

C870CF35400AA0J

KEMETIn Stock: 1170C870CF35400AA0J Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the 21FD3740 is determined by the following critical parameters:

Primary Substitution Criteria:

• Capacitance value: 40 µF (exact match required)
• Dielectric material: Polypropylene (PP), Metallized (required for application compatibility)
• Package style: Radial, Can configuration (mechanical fit requirement)
• Voltage rating: Equal to or greater than 370V AC (safety and reliability margin)
• Tolerance: ±10% or tighter (functional equivalence)

Secondary Compatibility Factors:

• Mounting configuration: Chassis mount capability
• Termination type: Quick Connect compatibility
• Operating temperature range: Minimum -40°C to 70°C coverage
• Product status: Active production status preferred for long-term availability

The KEMET C870CF35400AA0J meets the primary substitution criteria with a higher voltage rating (470V AC) and tighter tolerance (±5%), making it functionally equivalent for the specified applications.

Parameter Comparison

Engineering Selection Recommendations

Cornell Dubilier Electronics 21FD3740 (Primary Part):

• Select when RoHS non-compliant status is acceptable for the application
• Preferred for applications with strict temperature floor requirements (-40°C minimum)
• Suitable for designs already qualified to the MPF series specifications
• Adequate inventory availability supports production schedules

KEMET C870CF35400AA0J (Substitute Part):

• Select when ROHS3 compliance is a regulatory or design requirement
• Higher voltage rating (470V AC versus 370V AC) provides additional safety margin in motor run and PFC applications
• Tighter tolerance (±5% versus ±10%) supports applications requiring closer capacitance control
• Extended upper operating temperature limit (85°C versus 70°C) accommodates higher ambient or component temperature environments
• Stud mount configuration may require mechanical redesign compared to holder/bracket mounting of the original part
• Adequate inventory availability supports production schedules

Both parts are active production items with equivalent capacitance, dielectric material, and radial can package configuration. Selection between them depends on compliance requirements, thermal operating conditions, and mechanical mounting constraints specific to the application.

Frequently Asked Questions (FAQ)

Q: Can the KEMET C870CF35400AA0J directly replace the Cornell Dubilier 21FD3740 in existing designs?

A: Electrical substitution is valid based on matching capacitance (40 µF), dielectric material (polypropylene metallized), and voltage rating (470V exceeds 370V requirement). However, mechanical mounting differences exist: the KEMET part uses stud mount configuration while the original uses chassis mount with holder/bracket. Physical board layout and mechanical fixture modifications may be required.

Q: What is the significance of the voltage rating difference (370V versus 470V)?

A: The KEMET substitute has a higher voltage rating, which provides additional safety margin and derating capability in the application. Both parts are suitable for 370V AC operation; the higher rating does not affect functional performance in this application.

Q: Does the tolerance difference (±10% versus ±5%) affect substitution validity?

A: The KEMET substitute has tighter tolerance (±5%), which is more stringent than the original specification (±10%). Tighter tolerance is functionally compatible and may improve circuit performance in applications sensitive to capacitance variation. No design changes are required.

Q: What are the implications of the RoHS compliance difference?

A: The Cornell Dubilier 21FD3740 is RoHS non-compliant, while the KEMET C870CF35400AA0J is ROHS3 compliant. Selection depends on regulatory requirements for the end application and geographic market. ROHS3 compliance is required for products sold in the European Union and other regulated markets.

Q: Are there temperature range considerations for substitution?

A: The Cornell Dubilier part operates from -40°C to 70°C, while the KEMET substitute operates from -25°C to 85°C. The KEMET part has a higher minimum operating temperature (-25°C versus -40°C) but extends the maximum operating temperature. Applications requiring operation below -25°C must use the original Cornell Dubilier part.

Q: How do the lead spacing and physical dimensions affect substitution?

A: The Cornell Dubilier 21FD3740 has 0.813" (20.64mm) lead spacing with 1.875" (47.63mm) diameter and 4.000" (101.60mm) height. The KEMET C870CF35400AA0J has 0.528" (13.40mm) lead spacing with 1.772" (45.00mm) diameter and 3.937" (100.00mm) height. These dimensional differences require mechanical redesign of mounting fixtures and board layout.

Q: What is the application compatibility between these parts?

A: Both parts are specified for motor run and power factor correction (PFC) applications. The polypropylene metallized dielectric construction and radial can package are standard for these applications. Electrical performance is equivalent for the specified use cases.