Relay is a kind of electrical control equipment commonly used in industrial production and our lives. In layman's terms, it is a controllable switch. When the set conditions are met, the controlled circuit can be closed or opened. [1]
1. The structure of the relay
Although the operating principle and structure of the relay are different, they are all composed of the following three parts:
1. Sensing mechanism (accepting input signal): Sensing mechanism (input part) that can reflect certain input variables (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.), input loop.
2. Comparison mechanism (providing comparison value): between the input part and output part of the relay, there is also an intermediate mechanism (drive part) for coupling and isolating the input, function processing and driving the output part.
3. Actuator (output switch signal): the actuator (output part) that can achieve "on" and "off" control of the controlled circuit, and output loop.
Relay, generally refers to electromagnetic relay, that is, the kind of mechanical action. The essence of the role of the relay is to use a loop (usually a small current) to control the on and off of another loop (usually a large current), and in this control process, the two loops are generally isolated. Its basic principle is to use The electromagnetic effect is used to control the mechanical contacts to achieve the purpose of on and off, energizing the coil with the iron core-the coil current generates a magnetic field-the magnetic field attracts the armature to switch on and off the contacts. The whole process is "small current-magnetic-mechanical-large current". A process
Second, the form of relay contacts
1. Moving-on type (H type): The two contacts are disconnected when the coil is not energized, and the two contacts are closed when the coil is energized. It is represented by the pinyin prefix "H" of the ligature.
2. When the movable-break (D-type) coil is not energized, the two contacts are closed, and the two contacts are disconnected after energization. It is indicated by the pinyin prefix "D" of hyphenation.
3. Conversion type (Z type) This is a contact group type. This kind of contact group has three contacts in total, that is, the middle is a moving contact, and the upper and the lower are a static contact. When the coil is not energized, the movable contact and one of the static contacts are disconnected and the other is closed. After the coil is energized, the movable contact moves to make the original open to be closed, and the original closed to the open state to reach the converted state. Purpose. Such a contact group is called a changeover contact. It is indicated by the pinyin prefix "z" of the word "zhuan".
