Types of Solid State Relay (SSRs)

ElectronElectronics & ElectricalDigital Electronics

Depending on the applications and switching methods, the solid state relays (SSRs) are of following types −

  • Instant ON Solid State Relay

  • Zero Switching Solid State Relay

  • Peak Switching Solid State Relay

  • Analog Switching Solid State Relay

Instant ON SSRs

The instant ON SSR instantly switches on the load circuit when a sufficient input voltage is applied. It turns off when the input voltage is removed and the load current crosses the next zero. The instant ON SSRs are designed to control the inductive loads. The practical applications are in switching of contactors, magnetic valves, starters etc.

Zero Switching SSRs

A zero switching SSR switches on when an input voltage is applied and the load ac voltage crosses the next zero voltage. It switches off when the input voltage is removed and the load ac voltage reaches zero volts. A zero crossing circuit is used to achieve the operation of zero switching relay. The zero crossing circuit detects the zero cross of voltage and activates the TRIAC. The zero switching relays are mainly designed for controlling of resistive loads. Some applications are temperature control of heating elements, soldering irons, ovens etc.

Peak Switching SSRs

The peak switching SSR switches on when the output ac voltage reaches its next peak after applying the required control input voltage. It turns off after the removal of the input control voltage and the output ac current crosses its zero. A peak control circuit is used to detect the peak of output ac voltage and fires the TRIAC when the output ac voltage hits its peak.

These are used in control of switching of transformers, large motors and high inductive loads etc.

Analog Switching SSRs

The switching of analog switching SSRs depend on the amplitude of input voltage. The starting output voltage of analog switching SSRs being proportional to the input control voltage. It switches off when the control input voltage is removed and the output ac current crosses its zero. The analog switching SSRs are equipped with a synchronizing circuit that controls the amount of output voltage as a function of the control input voltage.

The analog switching SSRs are mainly designed for closed loop applications like temperature control.

raja
Published on 05-Jul-2021 09:55:57
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