Film Capacitors: Polyester, Polypropylene & Safety
Film capacitors for signal, power and AC applications
Film capacitors use a plastic-film dielectric and appear here as polyester/Mylar (MKT/MPE), polypropylene (MKP/CBB), selected polystyrene and PPS parts, plus application-specific AC motor and safety-rated listings. The chosen capacitance, voltage, tolerance and construction depend on the exact model and variant. A general-purpose DC film capacitor is not automatically suitable for connection across an AC mains line or operation in a motor.
Understand the formats in this collection
- Polyester film: Mylar, MKT and metallized polyester listings include small pF/nF values, radial and axial parts, and multi-value kits. Match dielectric, lead pitch and body size.
- Polypropylene film: MKP, CBB21/CBB22 and CBB81 listings include metallized and pulse/absorption designs, with option-specific voltage and capacitance. Do not infer pulse energy or snubber fitness from a CBB label alone.
- Audio crossover parts: radial and axial film capacitors are offered in several capacitance and voltage combinations. Select by crossover schematic, capacitor type, operating voltage and physical fit; “HiFi” in a title is not a performance specification.
- AC motor-run and fan capacitors: CBB61 listings present µF options and 450 VAC claims. Confirm the exact motor-run duty, AC rating, terminal style, dimensions and application before replacing a motor capacitor; a generic film part is not an equivalent starter or run capacitor.
- Safety capacitors: some X2 and Y2 listings, including 275 VAC X2 descriptions, appear here. X1/X2 across-the-line and Y1/Y2 line-to-earth positions have different safety requirements. Use only parts with verified class, approvals and applicable ratings for the intended location.
- Other dielectrics: polystyrene axial and small PPS SMD listings are distinct from the usual polyester and polypropylene radial parts.
How to select a film capacitor
- Define circuit location: signal coupling, filter, crossover, DC-link, snubber, motor AC or mains interference suppression.
- Choose capacitance in pF, nF or µF and verify tolerance; codes such as 103, 104 and 474 indicate nominal capacitance, not the entire electrical rating.
- Identify the exact dielectric, metallized or film-and-foil construction, and required operating temperature.
- Read voltage labeling carefully: a DC working-voltage marking does not establish an AC mains safety rating. AC voltage, surge, pulse and ripple limits are separate specifications.
- Measure lead pitch, body width, height and terminal arrangement. A matching capacitance may not fit the PCB or enclosure.
- For AC mains, motor or high-energy circuits, verify the manufacturer's datasheet, safety approvals and operating conditions for the actual part.
- Confirm the variant and pack quantity, particularly in mixed-voltage and assortment listings.
Electrical boundaries that matter
Polyester and polypropylene are not automatically interchangeable in high-current, high-frequency or high-pulse designs. “Non-inductive,” “low ESR” and “high ripple” claims apply only to identified parts and test conditions. A 1200 V IGBT absorption listing cannot establish a collection-wide snubber rating. A component described as 275 VAC X2 needs actual X2 markings and supporting approval evidence; this collection does not certify all members for direct mains use. Names such as WIMA, EPCOS or NISSEI in marketplace titles do not independently prove authorized origin.
Buying checklist
- Capacitance, tolerance and dielectric
- DC or AC voltage rating as applicable
- Safety class and verified approvals for mains use
- Pulse, dv/dt, ripple and temperature requirements
- Lead pitch, body dimensions and mounting orientation
- Motor duty or crossover topology where relevant
- Exact part number and quantity
Frequently asked questions
Can a 630 V DC film capacitor replace a 275 VAC X2 capacitor?
No. A DC rating is not a substitute for a verified across-the-line X2 safety class.
Are X2 and Y2 capacitors interchangeable?
No. They are intended for different mains circuit locations and require their own approved safety class.
Is every CBB61 capacitor a direct motor replacement?
No. Confirm the motor's required capacitance, rated AC voltage, duty, terminal style, dimensions and applicable safety requirements.
Does equal µF make polyester and polypropylene interchangeable?
No. Check loss, temperature, pulse and ripple demands as well as voltage and size.
