Do you know about the small problems of Relays?

Oct. 21, 2019

  In life, we will use a small micro switch of 0.5a in addition to the tact switch with a current of only 50ma. But today is the T78 Relay, which is often used in automated control circuits. It is actually an "automatic switch" that uses small currents to control high current operation. Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit. Relay: An automatic switch that essentially controls a large current with a small current. It has functions and functions such as automatic adjustment circuit, safety protection circuit and conversion circuit.

  In the process of applying relays, the problems that arise are numerous. So as a Power Relay Manufacturer today, I mainly talk about a problem when using relays: Why are relays often disconnected? Here are the reasons why I sorted them out.

Power Relay

Power Relay

  1. The load current is greater than the rated switching current of the SSR, which will permanently short the relay. In this case, the SSR with a larger rated current should be used. This is a theoretical statement. In fact, the rated current of the selected relay is not suitable. Simply speaking, when the load is greater than the minimum applicable load, the current can destroy the oxide film on the contact surface, reduce the contact voltage drop, and improve the signal transmission quality; when the load is less than the minimum applicable load, the oxide film and other factors may affect the contact performance of the contact. Although the relay can operate, the signal obtained by the switching is unreliable. Regarding the second problem, the load resistance is 0 ohms, when the voltage is not 0, the theoretical current is infinite, the relay contacts will burn out; if the voltage is 0, there is no signal, this problem has no meaning; the load voltage (this is called the signal voltage more) Appropriate) Small or even close to 0, can be considered as a small signal, suitable for signal relay requirements. The relays used for motor protection on the second floor do not have this requirement. The third floor believes that the principle of use of relays is that the rated current can only be large or small. Under normal circumstances, this statement is correct; but for signal relays, in addition to not higher than the rated current, it can not be lower than the minimum applicable load.

  2. At the ambient temperature where the relay is located, if the heat is not good, the output semiconductor device may be damaged. In this case, a larger or more effective heat sink should be used. Otherwise it will affect the relay often disconnected

  3. The line voltage transient causes the SSR output part to pass through. In this case, use a higher rated SSR or provide an additional transient protection circuit.

  4. The line voltage used is higher than the rated voltage of the SSR.

  Today, I would like to share with you the problem of frequent breaks in the relay. I hope that everyone can consider it when purchasing relays. If you find these problems after you buy them, you will be wasted your time and resources.

  Next, let's introduce Power Relay, a device that can be converted in one or more electrical output circuits when input (or excitation) meets certain conditions. It can be used in a neutral point direct grounding system as a directional component for zero sequence current protection.

Ningbo Baocheng Electronics Co., Ltd.

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