The
electric compressor’s activation relies on a multi-step process:
1. Pre-Charging
Before the compressor is fully operational, the vehicle’s high-voltage system undergoes a pre-charging phase. This step stabilizes the voltage and prevents current surges.
The electric compressor is equipped with a built-in pre-charging resistor module. The primary function of the pre-charging resistor is current limiting, controlled by the Battery Management System (BMS). It operates by connecting or disconnecting the pre-charging positive terminal of the high-voltage battery. Typically rated at 100Ω, the pre-charging resistor allows a small current to flow for specific purposes: detecting any short circuits in individual battery cells during pre-charging and gradually charging the capacitors in the motor controller and electric compressor controller when the vehicle is powered on. This gradual charging is necessary because the capacitors initially behave like a short circuit during the charging process.
Related Reading:
High Voltage Pre-charge Control Circuits in Electric Vehicles
2. Power Supply
Once pre-charging is complete, the high-voltage and low-voltage connectors simultaneously receive power.
3. Command Execution via CAN
The compressor's functionality is not automatically triggered by the power supply. Instead, the air conditioning controller sends specific instructions via the CAN network. These instructions dictate whether the compressor should activate, at what speed it should operate, and under what conditions it should shut down.
CAN communication offers numerous benefits in electric compressors:
- Precision: Real-time commands allow for fine-tuned operation, ensuring energy efficiency and system reliability.
- Diagnostics: Fault codes and performance data can be transmitted back to the controller for easy troubleshooting.
- Integration: CAN enables seamless interaction with other vehicle systems, such as battery management and climate control.
