The electric vehicle AC compressor transfers heat from the closed space to the outside, or brings heat from the outside into the closed space. There will be no heat generation in the process, but only heat transfer.
The compressor air conditioner on the electric vehicle is logically managed by the vehicle controller VCU, and its specific implementation forms are various. Here, only one typical form is used to illustrate its detailed working process.
Electrical Work Process
From an electrical point of view, the compressor air conditioner is mainly composed of the following parts: air conditioner controller, compressor and thermodynamic system, compressor motor and its controller, communication module, temperature and pressure sensor. As shown below.
Divide the electricity of the car air conditioner into two parts, the high-voltage part and the low-voltage part. As shown in the figure below, DC+ and DC- are high-voltage power supplies that are directly connected to the compressor motor controller. The “air conditioner relay” in the figure is the power switch of the air conditioner controller.
Compressor logic
The low-voltage part of the air conditioner is controlled by the VCU, and the VCU controls the on-off of the entire air conditioner by controlling the 12V power circuit “air conditioner relay”; transmits command information to the air conditioner controller through the CAN bus, and sets the target value of the working temperature; the air conditioner controller feeds back the air conditioner work to the VCU Status information, including on-off information of the power circuit switch, compressor pressure, compressor inlet and outlet temperature.
The high-voltage power supply of the electric air conditioning compressor comes from the on-board DC/DC converter. The air-conditioning controller controls the on-off of the contactor on the power circuit through the contactor trigger port, and then controls the working state of the compressor motor.
The compressor is integrated with the motor and motor controller that provide power for it, and the space is relatively small. Electromagnetic interference in the space is often the cause of the misoperation of the controlled motor.
Compressor motors generally use permanent magnet synchronous motors or permanent magnet DC brushless motors. There is no other reason, small size, simple control. The motor speed can be adjusted in a wide range according to the needs.
Turn the ignition switch of the electric vehicle to the “ON” position, and if the “A/C” switch of the air conditioner is turned on at this time, the air conditioner can start to work.
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Adjustment of cooling and heating capacity
The air conditioner controller closes the high-voltage circuit contactor, and the compressor enters the working state. Passengers adjust the temperature inside the car by adjusting the air volume and temperature setting buttons. The larger the air volume, the more heat will be brought into the car from the condenser, and the greater the power of the compressor will be required. The greater the difference between the set temperature and the current temperature, the greater the power of the compressor is required.
The air conditioner controller achieves the purpose of controlling the cooling and heating capacity by controlling the motor speed of the electric compressor. The motor speed is high, the corresponding operating speed of the compressor is increased, the refrigerant flow rate is increased, and the cooling capacity is increased.
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