How should the X/Y capacitors be configured for safety regulations in HMI (Human Machine Delivery) systems?

The configuration of HMI safety X/Y capacitors is crucial for equipment safety and EMC performance. X capacitors are connected between the power supply line (LN) and the ground line (FG) to filter differential-mode interference; their capacitance is typically 0.1μF to several μF. When selecting X capacitors, ensure their rated voltage is higher than the mains peak voltage and that they have safety certifications, such as X1 or X2. Y capacitors are connected between the power supply line and ground (FG) to filter common-mode interference. Their capacitance is smaller, typically between 1nF and 4.7nF, limited by safety standards for ground leakage current, such as stricter requirements for medical equipment. Y capacitors must be safety grade Y1 or Y2, with high withstand voltage and high reliability.

In configuration, a pair of Y capacitors is usually placed before and after the common-mode inductor to form a symmetrical structure, improving high-frequency common-mode rejection. After power is off, the charge stored in the X capacitors must be released through a discharge resistor to meet safety standards. On the PCB layout, the leads of the X/Y capacitors should be as short as possible and placed close to the common-mode inductor and filter terminals to reduce parasitic inductance and ensure high-frequency filtering performance. Eintech offers a full range of safety-certified X2 and Y2 capacitors, which can meet the dual requirements of safety and electromagnetic compatibility for HMI products, helping products pass rigorous certification tests.