The **MF-RX030/72** is a specific model of a **Resettable PTC (Positive Temperature Coefficient) Fuse**, manufactured by Bourns. These components are commonly referred to as **Multifuse®** or Polyfuses. Unlike standard fuses that blow and must be replaced, these devices "trip" by increasing their resistance significantly during an overcurrent or overtemperature event and reset once the fault is removed and the power is cycled. --- ### 1. Key Technical Specifications Below are the critical electrical parameters for the MF-RX030/72: | Parameter | Specification | Description | | :--- | :--- | :--- | | **Hold Current ($I_{hold}$)** | 0.30 A | The maximum current the device can carry without tripping. | | **Trip Current ($I_{trip}$)** | 0.60 A | The minimum current at which the device will switch to high resistance. | | **Rated Voltage ($V_{max}$)** | 72 V | The maximum voltage the device can withstand without damage. | | **Max Current ($I_{max}$)** | 40 A | The maximum fault current the device can safely interrupt. | | **Power Dissipation** | 0.66 W | Typical power dissipated when in the tripped state. | | **Resistance ($R_{min}$ / $R1_{max}$)** | 0.88 $\Omega$ / 2.10 $\Omega$ | Resistance range of the device at $23^\circ C$. | --- ### 2. Breakdown of the Part Number The part number follows a specific nomenclature used by Bourns: * **MF-RX**: Series prefix (Radial Leaded, Through-hole). * **030**: Represents the Hold Current (0.30 Amps). * **/**: Separator. * **72**: Indicates the maximum rated voltage (72 Volts). --- ### 3. Functional Features * **Radial Leaded Design:** These are through-hole components, making them ideal for PCB mounting where mechanical stability is needed. * **Self-Resettable:** Once the overcurrent condition is cleared and the temperature drops, the polymer returns to a conductive state. * **Safety Agency Recognition:** Usually UL, CSA, and TUV approved for safety standards. * **High Voltage Rating:** The "72" version is specifically designed for higher voltage applications compared to standard 30V or 60V models. --- ### 4. Common Applications * **Industrial Controls:** Protecting sensors and actuators. * **Power Supplies:** Secondary protection for transformers and DC power lines. * **Security Systems:** Overload protection for alarm panels and sensors. * **IEEE 802.3 Ethernet:** Used in Power over Ethernet (PoE) equipment. ---