## ESD-R-31C: Round Ferrite Core for EMI Suppression The **ESD-R-31C** is a high-performance, manganese-zinc (MnZn) ferrite core manufactured by **KEMET**. It is designed for electromagnetic interference (EMI) suppression in electronic circuits, specifically targeting noise in the lower frequency ranges. --- ### 1. Technical Specifications The following table outlines the physical and magnetic properties of the ESD-R-31C: | Parameter | Specification | | :--- | :--- | | **Material Type** | Manganese-Zinc (MnZn) | | **Outer Diameter (OD)** | 31.0 mm | | **Inner Diameter (ID)** | 19.0 mm | | **Thickness (HT)** | 13.0 mm | | **Operating Temperature** | -25°C to +85°C | | **Primary Function** | Low-frequency noise absorption | | **Coating** | Bare (Uncoated) | --- ### 2. Key Features and Mechanisms The ESD-R-31C operates as a passive component that suppresses unwanted high-frequency noise while allowing desired signals to pass. * **Noise Conversion:** It works by converting high-frequency electromagnetic interference into a small amount of heat through magnetic hysteresis and eddy currents. * **MnZn Material Advantage:** Unlike Nickel-Zinc (NiZn) cores which are better for high frequencies (MHz range), MnZn cores like the ESD-R-31C are optimized for **AM band and lower frequency ranges** (typically up to 10 MHz). * **Ease of Use:** As a "toroidal" or round core, it can be easily integrated by looping wires through the center. Increasing the number of turns increases the impedance exponentially. --- ### 3. Common Applications These cores are ubiquitous in both consumer and industrial electronics to ensure compliance with EMC (Electromagnetic Compatibility) standards. * **Power Supplies:** Suppressing noise on AC input lines or DC output cables. * **Industrial Equipment:** Protecting sensitive control signals from motor drive interference. * **Audio/Video:** Preventing "hum" or signal degradation caused by electromagnetic fields. * **Computing:** Used on data cables to prevent the cable from acting as an antenna for internal high-speed clock noise. --- ### 4. Selection Guide: Impedance vs. Frequency When using the ESD-R-31C, it is important to understand its performance curve. ```text Impedance (Ω) ^ | /---/ | / | _____/ | / +---------------------------> Frequency (MHz) 1MHz 10MHz 100MHz ``` *Note: Impedance increases as the frequency rises, peaking in the low MHz range before stabilizing.* ---