The **JR28-R-4LCT1** (often part of the Chint or generic industrial electrical series) is a **Thermal Overload Relay** designed primarily to protect AC motors from overheating, phase failure, and prolonged overcurrent conditions. --- ### ## Technical Specifications The following table outlines the typical electrical characteristics for this component: | Parameter | Specification | | :--- | :--- | | **Model Type** | Thermal Overload Relay | | **Setting Range** | Typically 0.1A to 93A (Specific to sub-model) | | **Poles** | 3 Phase | | **Auxiliary Contacts** | 1 NO (Normally Open) + 1 NC (Normally Closed) | | **Rated Voltage (Ue)** | Up to 690V AC | | **Tripping Class** | 10A (Standard) | | **Compatibility** | Often paired with CJX2 Series Contactors | --- ### ### Key Internal Components 1. **Bimetallic Strips:** The core sensing element. These consist of two metals with different expansion rates bonded together. When current flows through them, they heat up and bend. 2. **Trip Mechanism:** A mechanical linkage triggered by the bending of the bimetallic strips. Once the threshold is reached, it forces the auxiliary contacts to switch states. 3. **Current Adjustment Dial:** A potentiometer-style knob on the front face used to set the "Full Load Amps" (FLA) of the motor. 4. **Differential Mechanism:** Specialized internal levers that allow the relay to trip faster if one phase is lost (Phase Failure Protection). --- ### ### Operational Features * **Manual/Auto Reset:** A switch allows the user to choose whether the relay resets automatically after cooling down or requires a manual button press. * **Test/Stop Button:** Allows for manual testing of the trip mechanism to ensure the control circuit (NC contact) opens correctly. * **Temperature Compensation:** Designed to maintain consistent trip points despite variations in ambient room temperature (usually within -5°C to +40°C). ### ### Wiring Diagram Logic ```mermaid graph LR A[L1/L2/L3 Power] --> B[Contactor] B --> C[JR28 Thermal Relay] C --> D[3-Phase Motor] C -.-> E[Control Circuit - NC Contact] E -.-> F[Contactor Coil Cut-off] ``` ---