The **CMT4-4-R** is a specific model of a **Common Mode Choke** (Toroidal Inductor) manufactured by Coiltronics (a brand of Eaton). These components are primarily used for EMI (Electromagnetic Interference) filtering and noise suppression in power electronics. --- ### 1. Key Technical Specifications The CMT4-4-R is designed for high-frequency applications and high-current power lines. | Parameter | Specification | |:---|:---| | **Inductance (Typical)** | 1.0 mH | | **Rated Current** | 10.0 Amps | | **DCR (Direct Current Resistance)** | 11.0 mΩ (Max) | | **Mounting Type** | Through-Hole (Vertical) | | **Operating Temperature** | -40°C to +125°C | | **Core Material** | Ferrite | --- ### 2. Physical Construction The "CMT" series features a specific physical architecture: * **Toroidal Core:** The inductor uses a doughnut-shaped ferrite core which is highly efficient at containing magnetic flux, reducing cross-talk with nearby components. * **Winding Style:** It features two separate windings on the same core. In a common-mode configuration, these windings are wound such that they cancel out noise that is "common" to both lines (Phase and Neutral). * **Base Header:** The "4-4" designation often refers to the specific physical size and lead spacing, typically mounted on a plastic header for stability on a PCB. --- ### 3. Electrical Functionality The primary role of the CMT4-4-R is to act as a **Low Pass Filter**: 1. **Common Mode Suppression:** It provides high impedance to noise signals traveling in the same direction on both lines (e.g., noise from a switching power supply). 2. **Differential Mode Transparency:** It allows the desired power current (which flows in opposite directions) to pass through with minimal attenuation. 3. **Low DCR:** With a resistance of only 11.0 mΩ, it minimizes power loss and heat generation even at the full 10A load. --- ### 4. Typical Applications * **Switch Mode Power Supplies (SMPS):** Used at the input stage to meet FCC/CE EMI requirements. * **Industrial Electronics:** Filtering noise in motor controllers and heavy machinery. * **Uninterruptible Power Supplies (UPS):** Ensuring clean output power. * **Telecommunications:** Protecting sensitive data lines from AC power line interference. --- ### 5. Part Number Breakdown * **CMT:** Common Mode Toroid. * **4:** Size/Frame code (Refers to the physical dimensions of the core and header). * **4:** Specific winding/electrical characteristic variant. * **-R:** RoHS Compliant (Lead-free).