As a kind of relay, the principle of intermediate relay is the same as that of AC contactor. It is composed of fixed iron core, moving iron core, spring, moving contact, static contact, coil, wiring terminal and shell.

線圈通電，動鐵芯在電磁力作用下動作吸合，帶動動觸點動作，使常閉觸點分開，常開觸點閉合；線圈斷電，動鐵芯在彈簧的作用下帶動動觸點復位。

When the coil is energized, the moving iron core acts to pull in under the action of electromagnetic force, and the moving contact acts to separate the normally closed contact and close the normally open contact; When the coil is powered off, the moving iron core returns with the moving contact under the action of the spring.

一、代替小型接觸器

1、 Replace small contactors

中間繼電器的觸點具有一定的帶負荷能力，當負載容量比較小時，可以用來替代小型接觸器使用，比如電動卷閘門和一些小家電的控制。

The contact of intermediate relay has certain load capacity. When the load capacity is relatively small, it can be used to replace small contactors, such as the control of electric rolling gate and some small household appliances.

優點：不僅可以起到控制的目的，而且可以節省空間，使電器的控制部分做得比較精致。

Advantages: it can not only achieve the purpose of control, but also save space and make the control part of electrical appliances more exquisite.

二、增加接點數量

2、 Increase the number of contacts

這是中間繼電器常見的用法，例如，在電路控制系統中一個接觸器的接點需要控制多個接觸器或其他元件時而是在線路中增加一個中間繼電器。

This is a common use of intermediate relay. For example, when the contact of a contactor needs to control multiple contactors or other components in the circuit control system, an intermediate relay is added to the circuit.

三、增加接點容量

3、 Increase contact capacity

中間繼電器的接點容量雖然不是很大，但也具有一定的帶負載能力，同時其驅動所需要的電流又很小，(www.dgjs123.com電工技術之家)因此，可以用中間繼電器來擴大接點容量。比如一般不能直接用感應開關、三極管的輸出去控制負載比較大的電器元件。而是在控制線路中使用中間繼電器，通過中間繼電器來控制其他負載，達到擴大控制容量的目的。

Although the contact capacity of the intermediate relay is not very large, it also has a certain load capacity, and the current required for its driving is very small (www.dgjs123.com Electrotechnical home). Therefore, the intermediate relay can be used to expand the contact capacity. For example, the output of induction switch and triode can not be directly used to control electrical components with large load. Instead, the intermediate relay is used in the control circuit to control other loads through the intermediate relay, so as to expand the control capacity.

四、轉換接點類型

4、 Conversion contact type

在工業控制線路中，常常會出現這樣的情況，控制要求需要使用接觸器的常閉接點才能達到控制目的，但是接觸器本身所帶的常閉接點已經用完，無法完成控制任務。這時可以將一個中間繼電器與原來的接觸器線圈并聯，用中間繼電器的常閉接點去控制相應的元件，轉換一下接點類型，達到所需要的控制目的。

In the industrial control circuit, such a situation often occurs. The control requires the use of the normally closed contact of the contactor to achieve the control purpose, but the normally closed contact of the contactor itself has been used up and can not complete the control task. At this time, an intermediate relay can be connected in parallel with the original contactor coil, the normally closed contact of the intermediate relay can be used to control the corresponding components, and the contact type can be changed to achieve the required control purpose.

五、用作開關

5、 Used as a switch

在一些控制線路中，一些電器元件的通斷常常使用中間繼電器，用其接點的開閉來控制，例如如彩電或顯示器中常見的自動消磁電路，三極管控制中間繼電器的通斷，從而達到控制消磁線圈通斷的作用。

In some control circuits, the on-off of some electrical components is often controlled by the opening and closing of their contacts, such as the common automatic degaussing circuit in color TV or display, and the triode controls the on-off of the intermediate relay, so as to control the on-off of degaussing coil.