What are the Precautions for Relay Selection?

May. 14, 2020

In order to use the relay correctly, please understand the characteristics of the selected relay, confirm whether it is consistent with the relay's use conditions and environmental conditions, and be sure to master the coil usage method, contact method, and environmental conditions when the relay is actually used. Power Relay Manufacturer summarized the matters and points of attention that should be considered in the selection of relays.

GP Relay

GP Relay

1. Choose the correct model

To use the relay well, it is very important to select the correct type. First of all, we must have a thorough understanding of the nature, characteristics and use requirements of the controlled object, and carefully consider it. The principles, uses, technical parameters, structural characteristics, specifications and models of the selected relays must be mastered and analyzed. On this basis, the relay should be correctly selected according to the actual situation and specific conditions of the project.

2. Understanding of the contact point

When the relay coil is not energized, the static and dynamic contacts are called "normally open contacts", otherwise, they are called "normally closed contacts". A moving contact is normally closed at the same time with a static contact and normally open to another static contact, and they are called "switching contacts". In the same relay, there can be one or several pairs of normally open contacts or normally closed contacts (both can also have both), and can also have a set or array of conversion contacts.

3. Method to eliminate contact sparks

Because the current of the relay contact is small, there will be no arc between the contacts, but there will be "spark discharge". This is due to the presence of inductance in the contact circuit, then overvoltage will appear on the inductance when it is disconnected. It is added to the contact gap together, so that the contact gap just separated by a distance breaks down and discharges. Due to the energy limitation, only spark discharge will occur. The alternating conversion of the energy between the capacitor and the inductance between the contacts makes the spark discharge appear and disappear, which becomes a high-frequency signal, and the spark discharge will also cause damage to the contacts. And it will reduce the service life, so you must try to eliminate it. There are two practical spark suppression circuits. One. The basic working principle is to make the energy in the inductor pass through rc instead of the contact; Second. When disconnected, the diode v is consumed on the load r.l. Just choose one in the application. However, it should be noted that the rc parameter should be selected appropriately, and the parameter is mainly determined by experiment. Usually the capacitance c can be selected according to the load current 1a / 1 microfarad. When using diodes, the positive and negative polarities should be connected correctly.

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