The **JR28-R-DMCM1** refers to a specific series of **Thermal Overload Relays** designed for use in industrial motor control systems. These components act as protective devices to prevent electric motors from burning out due to overcurrent or phase failure. --- ### 1. Key Technical Specifications The following table outlines the general technical characteristics associated with the JR28 series: | Parameter | Description | | :--- | :--- | | **Component Type** | Thermal Overload Relay | | **Compatibility** | Typically used with CJX2 Series AC Contactors | | **Protection Type** | Overload and Phase Failure protection | | **Tripping Class** | Class 10A (Standard industrial protection) | | **Mounting** | Plug-in (Directly to contactor) or Independent mounting | | **Auxiliary Contacts** | 1 NO (Normally Open) + 1 NC (Normally Closed) | --- ### 2. Functional Components The "electronic" and mechanical operation of this part involves several critical internal and external elements: #### A. Bimetallic Strips The core "sensing" element. When the current exceeds the set value, the internal bimetallic strips heat up and bend at different rates. This mechanical deformation eventually triggers the trip mechanism. #### B. Adjustment Dial Located on the front face, this allows the user to set the **Full Load Amps (FLA)** of the motor. The relay will only trip if the current stays above this specific threshold for a predetermined time. #### C. Reset Mechanism (Manual/Auto) The "R" in the model often signifies the reset capability: * **Manual Mode:** Requires a technician to press the reset button after a fault. * **Auto Mode:** The device resets itself once the bimetallic strips cool down. #### D. Auxiliary Contacts (95-96 / 97-98) * **95-96 (NC):** Usually wired in series with the contactor coil to cut power when an overload occurs. * **97-98 (NO):** Used for signaling or alarms to notify a PLC or operator of a trip. --- ### 3. Wiring and Application In a typical setup, the JR28-R is plugged directly into the bottom of an **AC Contactor**. ```mermaid graph LR Power[L1, L2, L3] --> Contactor[CJX2 Contactor] Contactor --> Relay[JR28 Thermal Relay] Relay --> Motor[Electric Motor] ``` --- ### 4. Comparison: Thermal vs. Magnetic Unlike a circuit breaker which protects against **Short Circuits** (instantaneous high current), the JR28 is designed for **Overload** (sustained moderate overcurrent). It mimics the thermal profile of the motor to ensure protection without nuisance tripping during startup.