X-Capacitor Series Offers Improved EMI/RFI Protection

When designing power systems, a frequent major concern is how to handle electromagnetic interference (EMI) and radio frequency interference (RFI). To this end, one of the more fundamental components in AC systems is the X-capacitor.

 

Cornell Dubilier’s MXT series capacitors. Image used courtesy of Cornell Dubilier

 

Cornell Dubilier has released a family of X-capacitors designed to prevent interference and keep it from spreading.

 

What Is an X-capacitor?

X-capacitors are a fundamental component in electronic circuits, particularly in applications involving alternating current (AC).

These capacitors suppress electromagnetic interference and filter line disturbances in AC circuits. Their primary function is to bridge the active (line) and neutral conductors in an AC power supply, which helps reduce EMI entering and exiting the device. X-capacitors also play a crucial role in meeting regulatory standards for electromagnetic compatibility (EMC). 

 

An X-capacitor is used in “across-the-line” applications. Image by EEPower

 

X-capacitors are classified into two main categories: X1 and X2. X1 capacitors are designed for higher impulse voltage applications and are capable of withstanding voltages up to 4 kV. They are commonly used in industrial environments with more frequent transient voltages. On the other hand, X2 capacitors are rated for lower impulse voltages, typically up to 2.5 kV, and are used in more common consumer-grade appliances and electronics.

Constructed typically from materials like metalized polypropylene film, X-capacitors are known for their stability and safety features. These capacitors are designed to withstand high-voltage surges, ensuring consistent performance and reliability in various electrical environments. Due to their construction and material properties, X-capacitors exhibit self-healing characteristics. When a voltage spike occurs, only a small portion of the capacitor's dielectric is damaged, allowing it to continue functioning, albeit with a slightly reduced capacitance.

 

The MXT Series

The MXT series of capacitors are metalized polypropylene film capacitors designed to thrive in harsh environmental conditions like "across the line" class X2 applications and EMI/RFI suppression.

In terms of technical specifications, the MXT series offers a capacitance range of 0.1 µF to 40 µF, with a standard capacitance tolerance of ±10% and an optional ±20%. The capacitors are rated for 305 VAC and 630 VDC and are designed to operate within a temperature range of -40ºC to +110°C, with a voltage derating factor of 1.35% per degree Celsius above 85°C. 

 

Applications for the MXT series include inverters and utility meters. Image used courtesy of Cornell Dubilier

 

The life expectancy of these capacitors is noteworthy, with a rating of 100,000 hours at the rated voltage and a hotspot temperature below 85°C. They also demonstrate resilience in damp heat steady state conditions, maintaining a capacitance change rate of ≤±10% and showing a dissipation factor of .001 @ 1 kHz @ 20°C. 

Safety and compliance are key aspects of the MXT series, as the parts are encapsulated in a self-extinguishing resin within a plastic box meeting UL 94V-0 requirements. They meet several safety standards, including UL 60384-14, CSA-E60384-14, and IEC 60384-14:2013, ensuring their reliability and quality across various applications. 

 

A Crucial Component

X-capacitors offer a critical solution to contemporary challenges in electromagnetic interference suppression and circuit stability. Looking forward, integrating X-capacitors into more sophisticated power systems like renewable energy and smart grid technologies presents significant potential. Their ability to mitigate EMI effectively will be essential to ensuring system efficiency and reliability, increasingly central to modern energy infrastructure. Additionally, as electronic devices become more interconnected, X-capacitors' role in maintaining EMC standards becomes more critical. With the new family from Cornell Dubilier, the company hopes to provide the marketplace with a solution to such challenges.