What is the difference between Zero Current and Zero Voltage Switching

Zero Voltage Switching (ZVS) switches when the voltage is zero and is different to Zero Current Switching (ZCS) which switches when the voltage and current are both zero; referred to as the “zero-crossing” in a sinewave. ZVS is easier to implement into relay-based devices and whilst it works well for capacitive loads (switch mode power supplies). Zero voltage switching is not suitable for inductive loads including transformers and motors. Closing a relay contact when the voltage is zero is important for switching power supplies (switch mode power supplies: SMPS) of the type found in modern IT, computer and server loads.