Zero-crossing and random turn-on describe when an AC solid state relay begins conducting after receiving an input signal. The correct choice depends on the load and the required control method.
A zero-crossing SSR waits until the AC waveform is close to its zero-voltage point before turning on. This can reduce switching interference and current transients in suitable resistive-load applications.
A random turn-on SSR can begin conducting shortly after the control signal is applied rather than waiting for the next zero crossing. It is considered when immediate switching or phase-related control is required.
Resistive heaters, motors, transformers and capacitive loads behave differently during switching. The load's inrush current and control method must be reviewed together with the SSR output rating.
Confirm input voltage, pulse timing and switching frequency. Phase-control systems require compatible devices and control logic; a standard zero-crossing relay is not a substitute.
Switching mode does not remove the need for current margin, heat dissipation, overcurrent protection and overvoltage protection.
Browse XURUI solid state relays and provide the load and control parameters before selecting a switching mode.
