The **JR28-R-DMDP215** is a specific model of an **Overload Thermal Relay**, typically associated with the Chint or generic industrial electrical component series. These devices are designed to protect electric motors from overheating, phase failure, and sustained overcurrent conditions. --- ### 1. Key Technical Specifications The following table highlights the electronic and physical characteristics of the JR28 series: | Parameter | Specification | | :--- | :--- | | **Component Type** | Thermal Overload Relay | | **Current Setting Range** | Typically 0.1A to 93A (specific to model suffix) | | **Trip Class** | 10A (Standard) | | **Auxiliary Contacts** | 1 NO (Normally Open) + 1 NC (Normally Closed) | | **Mounting** | Direct plug-in to Contactor or Independent DIN Rail | | **Standard Compliance** | IEC/EN 60947-4-1, GB/T 14048.4 | --- ### 2. Functional Components The "electronic" logic of this device is primarily electromechanical, relying on thermal expansion. * **Bimetallic Strips:** The core sensing element. These expand at different rates when heated by current. If the current exceeds the set limit, the strips bend sufficiently to trigger the trip mechanism. * **Adjustment Dial:** A rotary potentiometer-style dial on the front face that allows the user to set the precise "Full Load Amps" (FLA) of the motor. * **Test/Stop Buttons:** * *Red Button:* Manual trip test or emergency stop. * *Blue Button:* Reset functionality (can be toggled between Manual and Auto reset). * **Differential Protection Mechanism:** Detects phase imbalance. If one phase loses current, the internal mechanism shifts to trip the relay faster to prevent motor burnout. --- ### 3. Wiring and Integration In a typical motor control circuit, the JR28 is wired in series with the main contactor. ```mermaid graph TD A[Power Supply] --> B[Contactor] B --> C[JR28 Overload Relay] C --> D[AC Motor] C -.-> E[Control Circuit/Alarm] ``` #### Contact Functions: 1. **NC (95-96):** Wired in series with the contactor coil. When a fault occurs, this opens, cutting power to the coil and stopping the motor. 2. **NO (97-98):** Used for signaling. When the relay trips, this closes to activate a fault light or send a signal to a PLC. --- ### 4. Common Use Cases * **Industrial Pumps:** Protecting against dry-running or impeller blockage. * **Conveyor Systems:** Protection against mechanical jams causing current spikes. * **HVAC Fans:** Ensuring motor longevity by preventing overheating during voltage fluctuations.