An AC-output solid state relay and a DC-output solid state relay are designed for different load circuits. They should not be treated as interchangeable simply because their current ratings are similar.
The output type is determined by the load being switched. An AC load requires an SSR designed for the applicable AC voltage and frequency. A DC load requires a DC-output device with the correct voltage range and polarity requirements.
AC SSRs commonly use bidirectional semiconductor switching structures suitable for alternating current. DC SSRs use devices intended to control current in one direction. Their turn-off behavior and leakage characteristics differ.
The input control signal may be DC or AC depending on the model. A DC-control, AC-output SSR is common, but the letters used in model codes should always be verified against the product datasheet.
Solid state relays have off-state leakage current and on-state voltage drop. These values affect small loads, indicator lamps, sensitive inputs and heat generation.
Motors, transformers, solenoids and capacitive power supplies can draw high starting current. Resistive heaters behave differently. Select current margin and protection according to the actual load.
For AC loads, determine whether zero-crossing or random turn-on operation is required. For DC loads, confirm polarity, switching speed and any inductive-energy suppression needed.
See the XURUI solid state relay range and provide the control signal, load voltage, current and load type for model matching.
