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Electrical Symbols and Contact Forms of Relays

The relay is composed of two parts, that is, coil and contact group. Thus, the graphic symbol of the relay in the circuit diagram also includes two parts, that is, a long box represents the coil, and a set of contact symbols represent a combination of contacts. When the circuit with few contacts is relatively simple, the contact group is often drawn directly on the side of the coil frame. This drawing method is called centralized representation. If the relay has two coils, and then usually two long boxes side by side are drawn. At the same time, the relay symbol J is marked in the long box or long box side.

There are two ways to represent the contacts of relay. One is to draw the contacts of relay directly on the side of the long box, which is more intuitive. Another is to draw each contact into its own control circuit according to the needs of circuit connection. Usually, the contact of the same relay and the coil are marked with the same text symbol, and the contact is grouped with a number to show the difference.

There are three basic forms of relay contacts. First one, the two contacts are disconnected when the moving-closing type (normally open or H-type) coil is not energized, and the two contacts are closed after energized. It is represented by the pinyin prefix H of the combined character. Second one, the dynamic break type (normally closed or D-type) coil is not energized when the two contacts are closed, and the two contacts are disconnected after the power. It is represented by the alphabetic word D. Last one, the conversion Z-type, which is the contact group type. The contact group has a total of three contacts, that is, the middle of a moving contact, a static contact above and below in each position. When the coil is not energized, the moving contact and one of the static contacts are disconnected and the other is closed. After the coil is energized, the moving contact will move, so that the original open shifted into closed, and the original closed shifted into open station in order to achieve the purpose of conversion. The group of such contacts is called transition contacts, which is represented by the pinyin Z of the world turn.

Post time: Aug-08-2022