How to Maintain Solid State Relay?

Solid state relay, short for SSR, is a non-contact switch composed of microelectronic circuits, discrete electronic devices, and power electronic power devices. The isolation device is used to realize the isolation between the control terminal and the load terminal.

The input end of the solid state relay uses a tiny control signal to directly drive a large current load. So, how to maintain a solid state relay? In this article, will introduce something about this topic.

  1. The controlled load will generate a large surge current at the moment of switching on. Since the heat is too late to dissipate, it is likely to damage the thyristor inside the SSR. Therefore, the user should analyze the surge characteristics of the controlled load when selecting the relay, and then Select relay. Generally, the above principles are followed when selecting. When low voltage requires small signal distortion, DC solid-state relays that use field effect transistors as output devices can be used. For AC resistive loads and most inductive loads, zero-crossing relays can be used. Extend the life of loads and relays, and also reduce their own radio frequency interference.
  2. When the relay is used, the internal output thyristor of the SSR solid state relay will be permanently damaged due to overcurrent and load short circuit. Consider adding a fast fuse and an air switch to the control loop to protect it (the product output protection should be selected for the selection of the relay, built-in varistor absorbing loop and RC buffer can absorb surge voltage and improve dv/dt tolerance); RC absorbing loop and varistor (MOV) can also be connected in parallel at the relay output to achieve output protection. The selection principle is to use 500V-600V varistor for 220V, and 800V-900V varistor for 380V.
  3. When the input voltage is too high or the input current exceeds its specified rated parameters during use, it can be considered to connect a voltage divider resistor in series at the input end or connect a shunt resistor in parallel at the input port so that the input signal does not exceed its rated parameter value.
  4. In specific use, the control signal and load power supply should be stable, and the fluctuation should not be greater than 10%, otherwise, measures should be taken to stabilize the voltage.