• Home
  • Industrial Controls, Meters
  • What is the working principle of solid state relays?

    * Question

    What is the working principle of solid state relays?


    The solid state relay is a kind of four-terminal device with two terminals as the input terminals and the other two terminals as the output terminals. The isolation device is used to realize the electrical isolation of the input and output.Solid state relays can be classified into AC type and DC type according to the type of load power supply.According to the switch type, it can be divided into normally open type and normally closed type.When the VIN is removed and the load current is lower than the triac holding current (AC commutation), the SSR turns off.

    The Z-type SSR internally includes a zero-crossing detection circuit. When the input signal VIN is applied, the SSR can be turned on only when the load supply voltage reaches the zero-crossing zone, and may cause the maximum delay of the power supply for half a cycle.When an inductive load is applied, the triac is turned on before the input signal is turned off, and the current lags the power supply voltage by 90O (when pure sense).At time t1, the input control signal is cancelled, and the triac is turned off (t2) when it is less than the sustain current. The thyristor will withstand a reverse voltage with a high voltage rise rate dv/dt.The unidirectional thyristor (enhanced SSR) is limited to the quiescent voltage rise rate (typically 200V/s) due to its unipolar operation. Therefore, the enhanced solid state relay HS series is replaced by the common SSR.

    Increased the dv/dt indicator by 520 times.In high-power applications, enhanced SSR, whether inductive or resistive, withstand voltage, current surge and product reliability, exceeds ordinary solid state relays and meets the basic specifications of imported products. It is an alternative to ordinary solid state relays.Updated product.


    DISQUS: 0