|General Purpose, 10A, 25A (AD-SSR2 / AD-SSR8 Series)|
Solid State Relays: Operational Overview
Solid state relays (SSR) are similar to electromechanical relays, in that both use a control circuit and a separate circuit for switching the load. When voltage is applied to the input of the SSR, the relay switch is energized by a light emitting diode. The light from the diode is beamed into a light sensitive semiconductor which, in the case of zero voltage crossover control relays, conditions the control circuit to turn on the output of the solid state relay switch at the next zero voltage crossover.
In the case of non-zero voltage crossover relays, the output of the solid state switch is turned on at the precise voltage occurring at the time. Removal of the input power disables the control circuit and the solid state relay switch is turned off when the load current passes through the zero point of its cycle.
Solid state relays have additional advantages which electromechanical relays do not, such as:
- Long life, Shock and vibration resistance, No generation of RFI, EMI
- No contact bounce, Arcless switching, No acoustic noise
- Zero crossing, IC compatibility