The HVDC relays function within charging devices by switching the DC power according to the generally accepted protocols like : Chademo, CSS, etc.
Especially in the fast DC chargers these relays are used. Reason is the fact that the fast chargers are charging the vehicles directly with a DC voltage. DC voltages of 450VDC and 1000 VDC applications are available.
Roughly, DC charging stations currently could be devided in three main power levels: ≤ 50 kW for city use, 150 kW for highways, and 350 kW for cars, trucks and buses. DC fast chargers usually include smaller subunits (12,5 KW, 20 KW, 25 KW) and then stack them up to create a higher power DC charging system. The ≤ 50kW power level category for city use shows the biggest growth according to market studies.