The part number **47LAC-250W-R** typically refers to a high-power **Metal Clad Wirewound Resistor**. These components are designed for high-power dissipation and are commonly housed in an aluminum casing for heat sink mounting. Below is a detailed breakdown of its specifications and functions. --- ### 1. Specification Overview | Feature | Description | | :--- | :--- | | **Component Type** | High-Power Metal Clad Wirewound Resistor | | **Power Rating** | 250 Watts (when mounted on an appropriate heat sink) | | **Resistance Code** | "47L" or "47" usually denotes **47 Ohms** | | **Tolerance** | "R" typically signifies a **±10%** or specific precision rating (standard is J: 5% or K: 10%) | | **Construction** | Wirewound core inside an extruded aluminum housing | | **Cooling** | Conductive cooling (must be bolted to a metal chassis) | --- ### 2. Key Technical Features * **Heat Dissipation:** The aluminum gold-anodized or silver-finished housing is designed to transfer heat away from the resistive element. Without a heat sink, the power rating drops significantly (often to 20-30% of its rated capacity). * **Inductive Nature:** Because it is "wirewound" (a resistive wire wrapped around a ceramic core), it has inherent inductance. This makes it unsuitable for very high-frequency applications but excellent for power management. * **Durability:** These parts are highly resistant to vibration, moisture, and harsh environments due to the silicone or cement filling inside the aluminum shell. --- ### 3. Common Applications These resistors are used in heavy-duty electronic circuits where large amounts of energy need to be converted into heat: 1. **Dynamic Braking:** Used in motor controllers (VFDs) to dissipate energy generated when a motor slows down. 2. **Load Testing:** Used as a "dummy load" to test power supplies or amplifiers. 3. **Inrush Current Limiting:** Protecting circuits from high surges when power is first applied. 4. **Heating Elements:** Sometimes used as small heaters in controlled environments to prevent condensation in electronic enclosures. --- ### 4. Installation Requirements * **Thermal Paste:** It is highly recommended to apply thermal grease between the flat bottom of the resistor and the mounting surface to improve heat transfer. * **Wiring:** Due to the 250W rating, the lead wires or terminals must be of a sufficient gauge to handle the current without melting.