As the supporting infrastructure of electric vehicles, charging piles are indispensable to provide charging services for electric vehicles. At present, there are four main global charging piles: national standard, European standard, American standard and Japanese standard. Today's article will give you the basic knowledge and working principle of the national standard new energy charging pile for science popularization. Let's learn it together!

Classification and composition of charging posts

Charging piles are divided into AC charging piles and DC charging piles. The former is also called "slow charging", and the latter is also called "fast charging".  

（1） Principle and structure of AC charging pile

AC charging pile is a power supply device that is fixedly installed outside the electric vehicle and connected with the power grid to provide AC power for the electric vehicle on-board charger (i.e. the charger fixedly installed on the electric vehicle). The AC charging pile only provides power output and has no charging function. It needs to connect the on-board charger to charge the electric vehicle. It is equivalent to acting as a control power supply. AC charging is divided into single-phase AC and three-phase AC according to the number of AC charging phases; AC charging power includes 2KW, 3.3KW, 7KW, 11KW, 22KW, etc. The most commonly used is the household single-phase 220V 7KW charging pile.

The 7KW AC charging pile is mainly composed of pile body, LED indicator board, LCD display, card reader, auxiliary power supply, main control module, relay module, wiring bank, single-phase circuit breaker (air switch), surge protective device (lightning protector), intelligent ammeter, AC contactor, access control switch, emergency stop switch, charging gun, charging harness, etc. (At present, the single-phase 220V 7KW charging gun is equipped with five contact terminals with seven holes, and the three-phase 380V 22KW charging gun is equipped with seven full contact terminals.)

（2） Principle and structure of DC charging post

The DC charging pile is a power supply device that is fixed outside the electric vehicle and connected to the AC power grid, and can provide DC power for the power battery of the off board electric vehicle. The input voltage of the DC charging pile is three-phase four wire AC 380 V ± 15%, the frequency is 50Hz, and the output is adjustable DC through internal control rectification, New energy vehicle charging pile Directly charge the power battery of electric vehicles. Common power is 30KW, 60KW, 90KW, 120KW.

60KW charging pile generally consists of LED indicator board, LCD display screen, card reader, rectifier (two 30KW), wireless network module, switching power supply, main control board, anti reflection board, electronic lock, fuse, ammeter, (A+) air switch, leakage circuit breaker, lightning protector, single-phase air switch, shunt, cooling fan, etc.

(1) Charging post

The pile structure of charging pile is usually made of steel, aluminum alloy and other materials, with strong durability and stability.

(2) Charging module

Charging module is the core part of charging pile, including charger, controller, power supply and other components. The charger is the main component of the charging pile, which is responsible for converting the electric energy into the electric energy required by the electric vehicle. The controller is responsible for controlling the working state of the charger and various parameters during the charging process to ensure the safety and stability of the charging process. The power supply provides power for the charging module.

(3) Display screen

The display screen of the charging pile is usually used to display the status, charging progress, charging cost and other information of the charging pile. The types and sizes of display screens are different. Some charging posts in Liuzhou are also equipped with touch screens, which are convenient for users to use, realize human-computer interaction, and meet the personalized needs of different types of users.

(4) Accounting management module

The accounting management module calculates the current consumption amount, collects fees and prints bills according to the current real-time electricity price and consumed electricity and other data. To complete the accounting management task, the controller and embedded printer need to work together. The charging pile adopts the trapezoidal electricity price policy. The controller calculates the consumption amount and completes the charging. The printer communicates with the controller, and the controller sends the consumption information to the printer to print the bill details of this charging.

(5) Connecting cable

The connecting cable is the bridge between the charging pile and the electric vehicle, which is responsible for transmitting electric energy and data. The quality and length of the connecting cable directly affect the charging efficiency and safety. Some high-end charging piles are also equipped with an automatic wire winder, which is convenient for users.

(6) Safety protection device

The safety protection devices of charging piles include leakage protection, overcurrent protection, overvoltage protection, etc. These devices can effectively protect the safety of charging piles and electric vehicles.

Schematic diagram of AC contactor circuit

The design and manufacturing quality of the above six major parts directly affect the service life and safety of the charging pile. Therefore, attention should be paid to these aspects when purchasing the charging pile.

Operating principle of charging post

The AC power is input from the three-phase power grid, converted into DC power through the bridge uncontrolled rectifier circuit, filtered by the LCR circuit and sent to the high-frequency DC-DC power converter. The power converter outputs the required DC voltage through the direct to direct conversion, and charges the electric vehicle battery after the output filtering. Four modes of charging can be selected, namely, fixed power, fixed time, fixed amount and automatic (until full).

Charging structure diagram of electric vehicle

To sum up, the working principle of the charging pile can be summarized as combining the power supply, converter and output device, so as to change the voltage from low to high, convert the high voltage into a state that can provide power supply, and finally realize charging the electric vehicle.