The **MF-RX030/72** is a specialized electronic component known as a **Resettable Fuse** or a **Polymeric Positive Temperature Coefficient (PPTC)** device. It is manufactured by Bourns and is primarily used for overcurrent protection. --- ## 1. Technical Specifications The part number "MF-RX030/72" reveals specific electrical characteristics: | Parameter | Value | Description | | :--- | :--- | :--- | | **Hold Current ($I_{hold}$)** | 0.30 A | The maximum current the device will pass without tripping. | | **Trip Current ($I_{trip}$)** | 0.60 A | The minimum current at which the device will switch to high resistance. | | **Max 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 handle. | | **Resistance ($R_{min}$ / $R1_{max}$)** | 0.88 - 2.10 $\Omega$ | The resistance range of the device in its initial state. | | **Mounting Type** | Through-Hole | Radial leaded package for PCB mounting. | --- ## 2. How It Works Unlike a traditional one-time fuse that blows and must be replaced, the MF-RX030/72 "resets" itself after the fault is cleared and the temperature drops. 1. **Normal State:** The conductive polymer allows current to flow with very low resistance. 2. **Fault State:** If the current exceeds the trip point, internal $I^2R$ heating causes the polymer to expand and turn non-conductive (high resistance). 3. **Reset State:** Once power is removed and the device cools down, the polymer contracts, and the conductive paths are restored. --- ## 3. Physical Characteristics and Packaging * **Package Style:** Radial Leaded (resembles a ceramic disc capacitor). * **Material:** Cured, flame-retardant epoxy polymer meeting UL 94V-0 requirements. * **Lead Material:** Tin-plated copper. ### Applications * **Security Systems:** Protecting sensors and control panels. * **Industrial Controls:** Protecting small motors or internal circuitry. * **Power Supplies:** Short-circuit protection for low-voltage power rails. * **Telecom:** Protection against power surges on communication lines. --- ## 4. Part Number Breakdown ```text MF - RX 030 / 72 | | | | | | | +---- Maximum Voltage Rating (72 Volts) | | +---------- Hold Current (0.30 Amps) | +------------- Series Name (Radial Leaded RX series) +------------------ Multifuse® Product Category ```