The part number **HFE28-140/24-2SHT1-R** refers to a high-power **Magnetic Latching Relay** typically manufactured by **Hongfa**. These relays are designed for high-current switching applications, common in smart meters, EV charging stations, and solar inverters. --- ### 1. Part Number Breakdown Based on standard Hongfa nomenclature, here is the technical breakdown of the code: | Segment | Meaning | Technical Specification | | :--- | :--- | :--- | | **HFE28** | Series Name | High-power magnetic latching relay series. | | **140** | Contact Rating | Maximum switching current is **140A**. | | **24** | Coil Voltage | Nominal operating voltage of **24VDC**. | | **2S** | Coil Type | **Double Coil** (Two-winding latching). | | **H** | Contact Form | **1 Form A** (Normally Open). | | **T** | Contact Material | Typically **AgSnO2** (Silver Tin Oxide) for high inrush loads. | | **1** | Version/Type | Specific design iteration or mounting style. | | **R** | Compliance | **RoHS** compliant. | --- ### 2. Key Technical Features * **Latching Mechanism:** Unlike standard relays, this is "bistable." It uses a permanent magnet to stay in the last position (Open or Closed) without needing continuous power to the coil. It only requires a brief pulse to switch states. * **High Power Handling:** Rated for **140A** at 250VAC, making it suitable for industrial and utility-grade power management. * **Low Power Consumption:** Because it only requires energy during the switching transition, it is highly energy-efficient for long-term monitoring systems. * **Dielectric Strength:** Usually features high isolation between the coil and contacts (often 4kV or higher) to protect control electronics from line surges. --- ### 3. Connection and Coil Operation Since this is a **2S (Double Coil)** model, the operation requires three pins for the coil (Common, Set, and Reset): | Action | Operation | | :--- | :--- | | **To Close (SET)** | Apply a 24V pulse to the "Set" coil. The contacts stay closed even after power is removed. | | **To Open (RESET)** | Apply a 24V pulse to the "Reset" coil. The contacts stay open even after power is removed. | --- ### 4. Typical Applications 1. **Smart Grid / Energy Meters:** Remotely disconnecting or reconnecting customer power. 2. **EV Chargers (EVSE):** Managing the high-current flow to the vehicle battery. 3. **Solar Inverters:** Grid-tie disconnection and safety switching. 4. **HVAC Systems:** Controlling heavy motor loads or heaters.