Intermediate Relay, Standard Components For Electrical Cabinets, Control Electrical Components

Intermediate relay, as the name suggests, is a relay that serves as an intermediate converter and bridge in a circuit. Its essence is an electromagnetic relay with slightly larger contact capacity and a larger number of contacts. Its core function is not to directly control high-power loads (such as motors), but to act as an intermediary for controlling the transmission, amplification, isolation, and distribution of signals. Main functions and functions 1. Signal amplification and conversion ·Function: Use a weak control signal (such as DC24V low current signal output from PLC, temperature controller, sensor) to control a larger capacity and higher voltage circuit (such as AC220V contactor coil). ·For example, the output point of a PLC can only drive a load of 0.5A, while the coil of an AC contactor requires a current of 1A. At this point, an intermediate relay can be used, with the PLC driving the intermediate relay first, and then the contacts of the intermediate relay driving the AC contactor. 2. Increase the number and capacity of contacts ·Function: When a control signal needs to control multiple circuits simultaneously, multiple sets of contacts (normally open, normally closed) of an intermediate relay can be used to achieve "one to many" control. ·For example, to press a start button, it is necessary to simultaneously turn on the indicator light, sound the alarm siren, and provide power to a device. Three sets of normally open contacts of an intermediate relay can be used to control these three circuits separately. 3. Contact type conversion ·Function: Convert the contact types provided by the control signal. For example, on-site sensors only provide a normally open signal, but your logic requires a normally closed signal, which can be converted through the normally closed contacts of the intermediate relay. 4. Circuit isolation ·Function: Isolate the control circuit from the main circuit or circuits of different voltage levels (such as strong and weak electricity) to improve the safety and anti-interference ability of the system. The control signal drives the relay through electromagnetic induction, and the two are completely isolated electrically. 5. Implement simple logic control ·Function: By cleverly connecting the coils and contacts of multiple intermediate relays, simple logic functions such as "AND", "OR", and "NOT" can be achieved, forming a basic logic control circuit. working principle The structure of the intermediate relay is identical to that of a regular electromagnetic relay, following the classic principle of electromagnetic induction: 1. Excitation: When a rated voltage is applied to both ends of the coil, a current is generated in the coil, which in turn generates a magnetic field. 2. Attraction: The generated magnetic field attracts the internal armature (armature) to move downward. 3. Action: The armature drives the moving contact to contact or separate from the stationary contact, thereby closing the normally open contact and disconnecting the normally closed contact. 4. Reset: When the coil is powered off, the magnetic field disappears, and the armature resets under the reaction force of the spring, restoring the contact to its original state. 4、 Main features and advantages ·Multiple contact numbers: There are usually multiple sets of normally open and normally closed contact combinations (such as 4 normally open and 4 normally closed, 2 normally open and 2 normally closed, etc.), which are very suitable for signal distribution. ·High sensitivity: The power required to drive the coil is very small, and it is easily driven by weak control signals. ·Compact in size and easy to install: It is usually installed using standard guide rails (such as TH35 guide rails), which can be densely installed and save control cabinet space. ·Fast action speed: both response and reset times are very short. ·High reliability: Due to its main use for controlling small current signals, its electrical lifespan (number of actions) is very long. Application scenarios Intermediate relay is one of the most fundamental and commonly used components in automation control systems and PLC systems 1. PLC output expansion: This is the most classic application. One output point of the PLC drives an intermediate relay, and multiple sets of contacts of this relay are used to control multiple execution components, greatly expanding the output capability of the PLC. 2. Electrical isolation: In industrial control, DC24V weak current is commonly used to control AC380V strong current. The intermediate relay can safely isolate these two circuits. 3. Complex logic control circuit: In traditional relay control circuits (such as machine tool circuits), complex functions such as interlocking, self-locking, and sequential starting can be achieved through the combination of multiple intermediate relays. 4. Instrumentation and DCS system: The output signals of process control systems (such as temperature controllers and pressure controllers) are controlled by intermediate relays to control on-site electric valves, pumps, and other equipment. 5. Household and commercial: Although different in size and form, the small relays on the control boards of air conditioners and refrigerators work similarly to intermediate relays, used to transmit weak electrical signals from the motherboard to high-power components such as compressors and fans. Intermediate relays are the "unsung heroes" in automation control systems. Although they do not directly drive the final equipment, they play an indispensable role in signal transmission, circuit isolation, and logic control. Proper use of intermediate relays can make control system design more flexible, safe, and reliable.