Charging station requirements:
IEC standard 61851-1 specifies the technical requirements for charging. There are currently four charging modes:
Mode 1: charge slowly on the household socket with protective contact (max. 16 a /230 v = 3.68 kW).
Mode 2: one to three-phase charging through reliable coding signal on the plug side.
Mode 3: electric vehicles with pilot and control contacts are charged through a specific charging connector system.
Mode 4: charger for fast DC charging through external control.
In modes 1 to 3, the power supply voltage can be supplied to the charger (OBC) integrated in the vehicle, which is converted into DC voltage and current according to the demand of regulating the battery. In mode 4, the vehicle provides DC voltage to regulate the current by feeding it back to the external power supply.
The common point of all charging systems is that the charging circuit is controlled by the charging circuit. Control must be switched and monitored. Therefore, basic relays are used in charging equipment. IEC 61851-1 stipulates that the use of charging station relays must comply with en 61810-1 finder relay standard. The largest relay has the advantage of disconnection (electrical network isolation). This is required by the standard. For semiconductors, it cannot represent this situation. When the charging process begins, the relay turns on voltage. Then, the semiconductor takes over to increase the load. Therefore, finder relay only needs to switch low load, and it can carry large current, which has a beneficial impact on the service life of the relay. In addition, the relay has the following advantages: when a fault occurs, the load unit can disconnect the power supply. The low power consumption and high current carrying capacity of the basic relay magnet system play a major role in the circuit board of the charging unit. The three-phase connected charging station (maximum 22 kW) can carry up to 32 A of current per wire. For these plug-ins, compact relays can be used.
Because heat dissipation requirements are really important in charging facilities, the following measures should be taken, and the circuit board should be reinforced with the following materials:
1. Copper wire is used to cool relay contacts.
2. Reducing the excitation voltage through pulse width modulation can significantly reduce the thermal output of the relay coil. The detector relay should be placed on the foot.
3. Air is installed between relay and housing.
4. PCB may circulate.
When used in mode 4, a special relay is required, which is included in the relay that can switch between high DC voltage and high current. In order to meet these requirements, several measures must be taken:
1. Contacts with special geometry and materials,
2. The contact chamber is full of gas, which can better extinguish the spark.
3. The blowing magnet has been successfully applied here.