The importance of applying safety capacitors in power electronic equipment (Part 1)
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The importance of applying safety capacitors in power electronic equipment (Part 1)

Posted Date: 2024-01-16

Safety capacitors reduce the effects of transient voltages and interference on electrical and electronic circuits, especially high-voltage applications, ensuring their safe operation. Safety capacitors are also used in everyday equipment such as telecommunications equipment such as modems, AC-DC power supplies, power distribution switches, and electric vehicles (EVs) and other automotive applications.

1. Advantages of safety capacitors

The main function of safety capacitors is to ensure safety. It protects the circuit from transient voltage spikes by transferring excess energy to ground based on circuit requirements. In addition, safety capacitors can filter electromagnetic interference (EMI). As more and more electronic devices enter the market, they can produce electromagnetic interference, causing equipment to malfunction, freeze, or fail. EMI filters resist interference and ensure a purer signal.

2. Types of safety capacitors

Safety capacitors are generally divided into two categories: Class X safety capacitors (Class-X) and Class Y safety capacitors (Class-Y), both of which can minimize EMI in different applications.

• Class X safety capacitors: Class X safety capacitors are also called "line-to-line capacitors" and are used between the conductors of input AC power. It provides wire-to-wire protection, and if it fails, a short circuit may occur, but there is no risk of electric shock. A fault usually results in a blown fuse or tripped circuit breaker.

• Class Y safety capacitors: Class Y safety capacitors are also called "line-to-ground capacitors" or "line bypass capacitors" and provide line-to-ground protection. If a ground fault occurs, there is a risk of electric shock. However, Y-class safety capacitors must meet strict specifications to minimize the chance of electric shock.

• X/Y class safety capacitor: A new safety capacitor formed by cleverly combining X1/Y2 class. This means that the capacitor can function as an X1 safety capacitor in line-to-line applications and as a Y2 safety capacitor in the line-to-ground portion of the circuit.


Figure 1. Schematic diagram of placement locations and related risks of Class X and Class Y safety capacitors.

Next week, we will continue to introduce you to how to choose appropriate safety capacitors and how Knowles Capacitors (KPD) can help you, so stay tuned!


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