Supporting All Your Safety Capacitor Needs

In high-voltage, high-reliability applications, safety is non-negotiable, which is why safety capacitors are essential. These passive components are engineered to mitigate the risks associated with transient voltages and electrical interference, helping protect both users and equipment from hazards, even in the event of component failure.

In Part 1 of our safety capacitor series, we introduced the role safety capacitors play in a circuit and in Part 2, we explored the distinctions between Class X and Class Y capacitors. Let’s briefly recap before diving into how we can help meet your needs with our safety capacitor offerings.

• Class X capacitors (also called across-the-line) are used between the wires carrying incoming AC current. These are designed to fail short, but without creating a shock hazard.
• Class Y capacitors (also called line-to-ground or line-bypass) are placed between the AC line and ground. If a ground failure occurs, there's a risk of electric shock, so these capacitors are built to fail open, minimizing that risk.

As shown in Table 1 below, these capacitors are further divided into subclasses based on factors like rated voltage and impulse voltage withstand capability.

*2x Y2 or Y4 rated may bridge double or reinforced insulation when used in series

Table 1. A high-level overview of the key specifications for a range of different safety-certified capacitor classes.

The Comprehensive Knowles Safety Capacitor Portfolio

At Knowles, we offer a broad range of safety-certified multilayer ceramic (MLC) and film capacitors designed to meet rigorous standards and support diverse applications from electric vehicle (EV) battery systems to industrial power supplies. Below is a breakdown of what we offer. 

Class X Safety Capacitors

Our Class X offerings range from 5.6 pF to 40 μF and are available in both MLCC and film formats.

Key options include:

• SYX/UYX family: These are both X1 and Y2 capacitors and are ideal for use in high-voltage EV battery systems
• MXT Class X2: Film capacitors that meet demanding 85/85 temperature-humidity-bias (THB) standards, making them ideal for use in harsh environments.

Class Y Safety Capacitors

Our Class Y safety capacitors, which are most commonly MLCCs, range from 5.pF to 1 μF and include the following options:

• SYX/UYX family
• SYS: Class X1/Y2 safety capacitors that have a humidity robustness grade III rating and 5kV impulse and a 1kVdc rating approved by TÜV and UL
• MYH series: Film capacitors that are AEC-Q200 qualified and meet a 2,000-hour THB life test. Ideal for use in many applications including motors, automated meter readers, uninterruptible power supplies (UPS), power supplies, charging systems, and appliances

Table 2 below provides a comparison of the characteristics of our Class Y safety capacitor offerings.

Table 2. A summary comparing many of our most popular Class X and Class Y capacitors.

A Real-World Example

Class X and Class Y capacitors often work in tandem within the same circuit. For example, Figure 1 shows a section of a schematic for an EMI filter board in and AC/DC power converter. In this example the input and output X capacitors are our MXT series film safety capacitors and the Y capacitors are SYS series MLCC safety capacitors.

Whether you’re designing electrical components for EVs, consumer appliances, or industrial systems, Knowles is sure to have a safety-certified capacitor that fits your needs, including our newly released extended range of enhanced safety capacitors.