The **JR28-R-DLCT1** is a thermal overload relay commonly used in industrial motor control circuits. It is designed to protect AC motors from overheating caused by overloads or phase failures. ### Technical Specifications | Feature | Description | | :--- | :--- | | **Model Series** | JR28 (Compatible with LC1-D series contactors) | | **Protection Type** | Thermal Overload / Phase Failure Protection | | **Contact Configuration** | 1 NO (Normally Open) + 1 NC (Normally Closed) | | **Reset Method** | Manual or Automatic (Switchable) | | **Tripping Class** | 10A (Standard industrial trip speed) | | **Mounting** | Direct plug-in to contactor or independent via DIN rail | --- ### Key Electronic & Mechanical Components #### 1. Bimetallic Strips The core "sensing" element. These consist of two bonded metals with different expansion coefficients. As current flows through them, they heat up and bend. If the current is too high (overload), the bending triggers the trip mechanism. #### 2. Adjustment Dial A rotary dial on the front face allows the user to set the **Current Rating (Ir)**. You must set this to the Full Load Amps (FLA) of the motor to ensure accurate protection. #### 3. Auxiliary Contacts (95-96 / 97-98) * **95-96 (NC):** Usually wired in series with the contactor coil. It opens during a fault, cutting power to the motor. * **97-98 (NO):** Usually wired to an external indicator lamp or PLC input to signal a "Fault" status. #### 4. Test & Stop Buttons * **Test Button:** Simulates a trip to verify the internal mechanism and auxiliary contacts are functioning. * **Stop Button:** Manually opens the NC contact to stop the motor, but does not "trip" the relay. --- ### Wiring Diagram Concept ```mermaid graph LR A[Power Supply] --> B[LC1-D Contactor] B --> C[JR28 Overload Relay] C --> D[AC Motor] subgraph Control Circuit E[NC 95-96] -- Interlocks with --> B F[NO 97-98] -- Alerts --> G[Fault Light] end ``` --- ### Typical Applications * **Conveyor Systems:** Protecting against mechanical jams that cause motor stall. * **Pump Stations:** Preventing motor burnout if the pump runs dry or becomes clogged. * **HVAC Fans:** Ensuring consistent current draw and protecting against phase loss in three-phase systems.