< br >
Time relay is a very important component in the electrical control system of time relay. Generally divided into power delay and power delay two types. From the principle of action there are electronic, mechanical and so on. Electronic is the use of capacitive charge and discharge and then with the principle of electronic components to achieve delay action. There are many types of mechanical types, such as air bags and springs. Horological escapement; There are also the use of small cover pole synchronous motor to drive the CAM, and now there will be more new time relays. The purpose of the time relay is to cooperate with the process requirements and execute the delay instruction. When the input physical quantity reaches the specified value, its electrical output circuit is switched on or blocked an automatic electrical appliance. Widely used in production process automation devices, power system protection devices, all kinds of remote, remote control and communication devices, is one of the most basic electrical components in modern automatic control systems. The relay generally consists of two parts: input sensing mechanism and output actuator. The former is used to reflect the change in the input amount, and the latter completes the contact turn-off action (for contact relays) or the on-off of semiconductor components (for contactless relays). Relays have jumping input-output characteristics. When the relay receives an input signal X, it does not operate until it reaches the operating value Xd, and the output jumps from zero to Ymax. The input signal continues to increase, and the output signal remains unchanged at Ymax. After the relay operation, if the input signal is reduced, the relay will only operate when the input is reduced to Xf, return to the starting position, and the output signal jumps back to zero. This property is called the relay property. Here, the input value that makes the relay start to operate (action value), the input maximum value that makes the relay return to the original state (return value), the rated voltage and current of the contact (rated value of the contact), and the time that the relay changes from one state to another state (operation time) are the main technical parameters of the relay. They not only represent the performance of the working process of the relay, but also the basis for selecting the relay. Relays come in a variety of categories. Such as electrical relay (its input can be current, voltage, frequency, power, etc.), non-electrical relay (its input can be temperature, pressure, speed, etc.); Protection relay, control relay; Contact relay, non-contact relay; Open (no protective measures for the main component), closed (with protective housing), sealed (no gas exchange inside and outside the housing) relays and so on. Commonly used relays classified according to the working principle are electromagnetic relays, polarized relays, reed relays, thermal relays and time relays. After the 20th century, relays have been greatly developed, and there have been magnetic contactless relays, semiconductor contactless relays, ASIC electronic time relays, solid-state relays, printed circuit board mounted (double in-line) relays, and protective relays with microprocessors and intelligent relays. Time relay is a kind of control electrical apparatus which realizes delay control by electromagnetic principle or mechanical principle. There are many kinds of it, there are air damping, electric and electronic type. Air damping type time relay is often used in AC circuit, which uses the principle of air throttling through small holes to obtain delay action
When the relay is working, the electromagnet is energized, and the armature is drawn down to make D and E contact, and the working circuit is closed. When the electromagnet loses its magnetism, the spring pulls the armature up and cuts off the working circuit. Therefore, a relay is a switch that uses an electromagnet to control the working circuit.
Advantages of using relays to control circuits: using low voltage to control high voltage; Remote control; Automatic control.