Relay contact wear reduction for electric vehicle supply equipment

A method for a turn on sequence of two relay switches, wherein in a state where both relays are turned off,

• determining, by a first detection circuit of a primary circuit, a period and phase of a supply voltage,
• turning on a first relay switch or a second relay switch of the two relay switches is turned on,
• determining, by a first and second detection circuit enclosed in a primary and secondary circuit, respectively, a period and phase of a supply voltage,
• calculating, the relay turn on delay time ton, based on the time period Tv of the supply voltage (3) and the relay close time tclose according to ton=Tv−tclose, and
• commanding the turn on of the yet turned off first relay switch or second relay switch, via a control unit based on a turn on delay time ton such that the yet turned off relay is turned on at or in close proximity to the zero crossing time of the supply voltage, wherein the turn on order of the two relays switches is reversed for each power switching cycle.