The part number **HFE28-140/12-2SHT2-R** refers to a high-voltage power relay, typically manufactured by **Hongfa**. These relays are specifically designed for New Energy Vehicles (EVs) and high-voltage DC switching applications. ### 1. Part Number Breakdown The nomenclature can be decoded as follows: | Code Segment | Meaning | Description | | :--- | :--- | :--- | | **HFE28** | Series Name | High-voltage DC Relay series (Magnetic Blow-out) | | **140** | Current Rating | Rated continuous carry current of **140 Amperes** | | **12** | Coil Voltage | Control circuit operates at **12V DC** | | **2S** | Contact Form | Dual contact set / Specific mounting orientation | | **HT2** | Housing Type | High-temperature resistant plastic or specialized sealing | | **R** | Feature/RoHS | Internal resistor/diode for suppression or RoHS compliance | --- ### 2. Key Technical Specifications Based on the standard HFE28 series parameters: * **Load Voltage:** Rated for up to **1000V DC** switching. * **Contact Resistance:** Typically $\le 1m\Omega$ (initial). * **Insulation Resistance:** $1000M\Omega$ (at 1000V DC). * **Dielectric Strength:** Usually 3000V AC or higher between coil and contacts. * **Life Expectancy:** * *Mechanical:* $2 \times 10^5$ operations. * *Electrical:* $1 \times 10^3$ operations (at max rated voltage/current). --- ### 3. Core Features and Technology The HFE28 series utilizes several advanced electronic design principles to handle high-power DC: #### A. Magnetic Blow-out Switching high-voltage DC is difficult because DC does not have a "zero-crossing" like AC. When the contacts open, an arc forms. This relay uses **permanent magnets** to "blow" the arc away from the contacts, stretching it until it extinguishes. #### B. Ceramic/Epoxy Sealing The contact chamber is often filled with inert gas (like Nitrogen or Hydrogen) and hermetically sealed. This prevents oxidation of the contacts and allows for a smaller gap to quench arcs effectively. #### C. Polarized Contacts Because of the magnetic blow-out feature, these relays are often **polarity-sensitive**. You must connect the positive (+) and negative (-) terminals of the high-voltage load to the correct pins as indicated on the housing. --- ### 4. Common Applications * **Electric Vehicles (EVs):** Main relay for the Battery Management System (BMS). * **Charging Stations:** DC fast-charging disconnects. * **Solar Inverters:** High-voltage DC side switching for PV arrays. * **Energy Storage Systems (ESS):** Battery rack protection. ---