The **ESD-R-57** belongs to a series of **Round Ferrite Cores** manufactured by KEMET (TOKIN). These components are designed specifically for electromagnetic interference (EMI) suppression. ### 1. Technical Specifications The ESD-R-57 is a larger-sized ferrite core typically used for cables and wiring. | Feature | Specification (Typical) | | :--- | :--- | | **Material** | Manganese-Zinc (Mn-Zn) or Nickel-Zinc (Ni-Zn) | | **Outer Diameter (A)** | 57.0 mm | | **Inner Diameter (B)** | 35.5 mm | | **Thickness/Height (C)** | 15.0 mm | | **Frequency Range** | High frequency (HF) to Very High Frequency (VHF) | | **Operating Temp** | -25°C to +85°C | --- ### 2. Core Functionality The ESD-R-57 acts as a passive low-pass filter. It works by: * **Impedance Induction:** Increasing the impedance of the conductor at high frequencies without affecting low-frequency signals or DC power. * **Energy Dissipation:** Converting high-frequency noise energy (EMI/RFI) into a small amount of heat through magnetic hysteresis and eddy currents. * **Common Mode Suppression:** When a cable (containing both live/neutral or signal/ground) is passed through the core, it effectively cancels out common-mode noise. --- ### 3. Key Characteristics * **Shape:** Toroidal (Ring) core. * **Coating:** These cores are often bare (gray) or coated with an epoxy/resin to provide insulation and protect the ferrite from chipping. * **Installation:** Unlike "Split Cores" (snap-on), the ESD-R series are solid rings. The cable must be threaded through the center during the assembly process. --- ### 4. Typical Applications The ESD-R-57 is commonly used in industrial and consumer electronics where large diameter cables are present: 1. **Power Supplies:** Suppressing noise on AC input lines. 2. **Motor Drives:** Reducing EMI generated by variable frequency drives (VFDs). 3. **Medical Equipment:** Ensuring sensitive diagnostic tools are not affected by external radiation. 4. **Office Automation:** Used in large-scale copiers and servers. --- ### 5. Selection Guide To maximize the effectiveness of the ESD-R-57: * **Turns:** Passing the wire through the hole multiple times (2-3 turns) increases the impedance significantly. * **Placement:** Position the core as close to the noise source or the entrance of the equipment as possible.