Metallized Polypropylene Class X2 Capacitors for Across-the-Line EMI Suppression

 

UF Capacitors X2 Safety Capacitors are metallized polypropylene film capacitors designed for across-the-line interference suppression and EMI filtering in AC mains applications.

Unlike general-purpose film capacitors, X2 capacitors are safety-rated components intended to be connected between the Line and Neutral (L-N) conductors of an AC power input. Their primary role is to suppress conducted electromagnetic interference, absorb switching noise and help electronic equipment meet EMC requirements while maintaining the required electrical safety performance.

UF supplies Class X2 capacitors in 275VAC, 305VAC and 310VAC versions, with capacitance values from approximately 0.001µF to 2.2µF. Standard products use metallized polypropylene film, radial leads and flame-retardant plastic cases sealed with epoxy resin.

 

What Is an X2 Safety Capacitor?

 

An X2 safety capacitor, also called an X2 interference suppression capacitor or across-the-line capacitor, is connected directly between the Line and Neutral conductors of the AC mains.

AC Line  ->  Fuse / Protection  ->  EMI Filter  ->  Rectifier / Power Supply

L  ---  X2 Capacitor  ---  N

The capacitor provides a low-impedance path for high-frequency differential-mode noise while allowing the 50/60Hz mains power to pass normally through the system.

 

• Suppressing conducted EMI on the AC power line
• Reducing differential-mode switching noise
• Filtering high-frequency interference generated by power electronics
• Supporting EMC compliance
• Reducing noise returned from equipment to the mains network
• Handling repetitive electrical transients within the X2 safety-class requirements

 

Because an X2 capacitor is permanently connected across the AC mains, it must meet specific safety standards. A normal polypropylene film capacitor should not be used as a substitute unless it has the required X2 safety approval.

 

UF X2 Safety Capacitor Key Specifications 

 

Parameter	UF X2 Safety Capacitor
Safety Class	Class X2
Dielectric	Metallized Polypropylene Film
Rated Voltage	275VAC / 305VAC / 310VAC
Capacitance Range	0.001µF-2.2µF
Standard Tolerance	±10%
Operating Temperature	-40°C to +110°C
Dissipation Factor	tgδ ≤ 0.0010 at 1kHz
Construction	Non-inductive metallized film
Case	Flame-retardant plastic case, epoxy sealed
Mounting	Radial through-hole
Packaging	Bulk / Ammo Tape available
Compliance	RoHS / REACH
Applications	AC-line EMI suppression, input filtering, interference suppression

 

Exact electrical characteristics, dimensions and approvals depend on the selected capacitance, voltage and part number. Always use the latest UF datasheet when approving a component for production.

 

275VAC, 305VAC and 310VAC X2 Capacitors

 

275VAC X2 Safety Capacitors

 

275VAC X2 capacitors are widely used in conventional AC mains interference-suppression circuits.

Current UF products include values such as:

 

• 0.033µF 275VAC
• 0.039µF 275VAC
• 0.068µF 275VAC
• 0.1µF 275VAC
• 0.15µF 275VAC
• 0.22µF 275VAC
• 0.33µF 275VAC
• 0.47µF 275VAC
• 0.82µF 275VAC
• 1.0µF 275VAC
• 1.5µF 275VAC
• 2.2µF 275VAC

 

305VAC X2 Safety Capacitors

 

305VAC X2 capacitors provide a higher AC voltage rating for applications where the circuit design, grid conditions or end-product requirements call for additional voltage margin. UF offers 305VAC versions across multiple capacitance values and lead pitches.

 

310VAC X2 Safety Capacitors

 

310VAC is another important voltage class in the UF X2 product family. Current UF listings include 310VAC products from small EMI-filter values such as 0.012µF, 0.015µF, 0.022µF and 0.047µF up to larger values including 0.47µF, 0.68µF, 0.82µF, 1.0µF, 1.5µF and 2.2µF.

The correct voltage rating should always be selected according to the actual mains voltage, applicable safety standard and circuit requirements rather than by capacitance alone.

 

Why Metallized Polypropylene Is Used for X2 Capacitors

 

Low Dielectric Loss

 

Low dissipation factor helps minimize internal heating during continuous AC operation.

 

Self-Healing Capability

 

The metallized film can self-heal after a localized dielectric breakdown. A very small area of metallization is cleared around the fault location, allowing the remaining capacitor structure to continue operating.

 

High Insulation Resistance

 

High insulation resistance helps maintain stable electrical characteristics in mains-connected applications.

 

Good AC Performance

 

Polypropylene film performs well under repetitive AC voltage and high-frequency interference conditions.

 

Long-Term Stability

 

Stable capacitance and low dielectric loss make metallized polypropylene a common dielectric technology for X2 safety capacitors.

 

Typical Applications of X2 Safety Capacitors

 

Switching Power Supplies

 

X2 capacitors are installed in the input EMI filter of AC/DC switch-mode power supplies to suppress differential-mode switching noise. Typical equipment includes industrial power supplies, computer power supplies, LED drivers, telecom power supplies and server power systems.

 

Home Appliances

 

Class X2 capacitors are commonly used in washing machines, refrigerators, air conditioners, microwave ovens, coffee machines, vacuum cleaners and kitchen appliances. They help control electrical interference generated by motors, switching power supplies and electronic control circuits.

 

Solar Inverters

 

Solar and photovoltaic inverters contain high-frequency switching stages that generate conducted EMI. X2 capacitors can be used in the AC-side EMI filter to reduce interference returned to the grid. For outdoor or high-humidity applications, designers should also consider UF's THB / Heavy Duty X2 Safety Capacitor versions.

 

UPS Systems

 

UPS equipment is normally connected to the AC mains for long operating periods. X2 safety capacitors are commonly used in input filters to suppress conducted interference generated by rectifier and inverter switching stages.

 

Motor Drives and Frequency Converters

 

Variable-frequency drives and industrial inverters generate significant high-frequency electrical noise. X2 capacitors are used in mains input EMI filters to help reduce differential-mode conducted interference.

 

EV Chargers and Wallboxes

 

AC EV charging equipment contains power-conversion and switching circuits that require EMI filtering. X2 capacitors can be used across the AC line in the input interference-suppression network, subject to the required safety approval and environmental qualification.

 

Smart Meters and Industrial Electronics

 

Smart meters, industrial controllers and other long-life mains-connected electronics commonly use X2 capacitors for AC input interference suppression.

 

X2 vs X1 vs Y Safety Capacitors

 

Capacitor Class	Typical Connection	Primary Function
X2	Line to Neutral	Across-the-line EMI suppression
X1	Line to Neutral	Across-the-line suppression with higher impulse requirements
Y1 / Y2	Line or Neutral to Earth	Line-to-ground common-mode EMI suppression

 

The key distinction is the installation position. X capacitors are connected across the AC line. Y capacitors are connected between Line/Neutral and protective earth or chassis.

Because a Y capacitor failure can create a potential electric-shock hazard, Y-class capacitors are subject to different safety requirements.

Do not replace an X2 capacitor with a normal film capacitor or substitute X and Y safety classes without reviewing the circuit and applicable safety standard.

 

X2 Safety Capacitor Lead Pitch and Case Size

 

Selecting an X2 capacitor is not only an electrical decision. UF provides multiple case sizes and lead pitches, including commonly used configurations such as 10mm, 15mm, 22.5mm and 27.5mm.

Before replacing an existing X2 capacitor, check:

 

• Capacitance
• Rated AC voltage
• Safety class
• Applicable approvals
• Capacitance tolerance
• Lead pitch
• Case length
• Case width
• Case height
• Lead diameter
• PCB clearance

A capacitor with the same capacitance and voltage may still be unsuitable if its mechanical footprint or safety approval differs from the original component.

X2 Safety Standards and Approvals

Safety certification is one of the most important differences between an X2 capacitor and a general-purpose film capacitor. UF's X2 capacitor specification references approval systems including:

 

• UL / cUL
• VDE
• ENEC
• KTL
• CQC
• IEC-CB

Applicable standards include IEC / EN 60384-14 and corresponding regional safety standards. The approved capacitance and voltage range can vary between certification bodies, so designers should verify the certificate associated with the exact UF part number before final production approval.

Standard X2 vs Heavy Duty / THB X2 Capacitors

Standard X2 capacitors are suitable for many indoor and controlled-environment EMI-filter applications.

For equipment exposed to:

 

• High humidity
• Condensation
• Outdoor installation
• Temperature cycling
• Long energized operating periods

a THB-rated X2 capacitor may be more appropriate.

THB means: Temperature + Humidity + Bias

In a THB test, the capacitor is exposed to elevated temperature and humidity while electrical voltage is applied.

UF also provides Heavy Duty X2 Safety Capacitors / THB Series for applications such as power meters, solar inverters and other equipment requiring additional environmental reliability.

The standard X2 and THB X2 series should therefore be selected according to the actual operating environment rather than assuming the higher THB level is necessary for every design.

 

How to Choose an X2 Safety Capacitor

 

1. Confirm the Safety Class

 

Verify that the capacitor is connected across Line and Neutral and that the circuit requires Class X2.

 

2. Select the Rated AC Voltage

 

Choose among 275VAC, 305VAC and 310VAC according to the circuit voltage and applicable safety requirements.

 

3. Select the Capacitance

 

Capacitance should be determined from the EMI-filter design. Common values include 0.01µF, 0.022µF, 0.047µF, 0.068µF, 0.1µF, 0.15µF, 0.22µF, 0.33µF, 0.47µF, 0.68µF, 1.0µF, 1.5µF and 2.2µF.

 

4. Verify Safety Approvals

 

Confirm that the exact capacitance and voltage combination has the certification required by your market.

 

5. Check Temperature and Environment

 

For standard indoor equipment, a conventional X2 product may be sufficient. For humid, condensing or outdoor applications, evaluate a THB-rated X2 capacitor.

 

6. Match the PCB Footprint

 

Verify lead pitch, case dimensions and available board space.

 

7. Check the Exact Part Datasheet

 

Do not approve a production replacement based only on X2 + capacitance + voltage. Mechanical dimensions, safety approvals and environmental requirements must also match.

 

FAQ

 

 

What is an X2 safety capacitor?

 

An X2 safety capacitor is an interference-suppression capacitor designed for connection across the Line and Neutral conductors of an AC mains input. It is commonly used to reduce differential-mode conducted EMI.

 

What is the difference between an X2 capacitor and a normal film capacitor?

 

An X2 capacitor is specifically designed and safety-approved for across-the-line mains applications. A general-purpose film capacitor may use a similar polypropylene dielectric but does not automatically have the required X2 safety qualification.

 

What voltage ratings are available for UF X2 capacitors?

 

UF currently supplies X2 safety capacitors in 275VAC, 305VAC and 310VAC versions, depending on capacitance and part number.

 

What capacitance range does UF offer?

 

The current UF X2 specification covers approximately 0.001µF to 2.2µF.

 

What is a 0.1µF X2 capacitor used for?

 

A 0.1µF X2 capacitor is a common value in AC mains EMI filters. The exact value should be selected according to the interference-suppression network and EMC requirements.

 

Can I replace a 275VAC X2 capacitor with a 305VAC or 310VAC X2 capacitor?

 

A higher rated AC voltage may be acceptable electrically, but the replacement must also meet the required safety approvals, capacitance, dimensions, lead pitch and circuit requirements.

 

What is the difference between X2 and Y2 capacitors?

 

X2 capacitors are normally connected across Line and Neutral. Y2 capacitors are connected from Line or Neutral to earth/chassis and are designed around different safety requirements because their failure can affect electric-shock protection.

 

What does MKP mean on an X2 capacitor?

 

MKP refers to metallized polypropylene film construction. It combines polypropylene dielectric with a thin metallized electrode and provides low loss and self-healing characteristics.

 

What is a THB X2 capacitor?

 

A THB X2 capacitor is an X2 safety capacitor additionally evaluated under combined Temperature, Humidity and electrical Bias. It is particularly relevant to humid, outdoor or long-life applications.

 

Are UF X2 safety capacitors safety certified?

 

UF's X2 specification lists multiple approval systems including UL/cUL, VDE, ENEC, KTL, CQC and IEC-CB. The exact approval must be checked against the selected capacitance and voltage configuration.

 

Need Help Selecting an X2 Safety Capacitor?

 

UF Capacitors supplies 275VAC, 305VAC and 310VAC metallized polypropylene X2 safety capacitors for AC mains interference suppression and EMI filtering.

To recommend the correct X2 capacitor, send us:

 

• Required capacitance
• AC mains voltage
• Required safety approvals
• Lead pitch
• Maximum case dimensions
• Operating temperature
• Humidity / THB requirement
• Annual quantity

UF engineering can then recommend an existing X2 part number or evaluate the appropriate standard or THB-rated X2 capacitor for your application.