Why do we need an electric compressor?
- The compressor of the air conditioner in a fuel car uses the power of the engine to compress the refrigerant.
- EV cars do not have an engine, so they use electric energy from batteries. Converts to motor control current using an inverter. Start the motor and compress the refrigerant in the compression area.
- The inverter receives instructions from the vehicle and instructs the operation (rotation speed) of the compression area.
- In conventional DC motors, these are mechanical contacts such as “brushes” and “commutators”. The brushes wear out due to long-term rotation, reducing the lifespan of the motor.
- Electric compressors do not have the mechanical contacts mentioned in no 4 above. Adopts brushless motor.
- Brushless motors have a built-in magnetic element or optical encoder for rotor position detection. This position detector sends a signal to the drive circuit. The motor winding is a 3- phase star connection. Additionally, the rotor uses permanent magnets.
- However, in order to rotate the motor, the electronic circuit (inverter) of the drive circuit, which is composed of IGBTs , is used to electrically switch the current and rotate the motor.
- How to drive a brushless motor. (Here in after referred to as IGBTs) are connected to the motor windings, and six IGBTs make up an inverter. The upper and lower IGBTs alternately turn on and off in a fixed order to change the direction of the winding current.
- Explain the mechanism of rotation. In the IGBT switching sequence shown below, in step 1, Tr1 and Tr6 of the IGBT are in the ON state. At this time, the winding current flows from the U phase to the W phase, and the U phase is excited to the north pole and the W phase to the south pole. This causes the rotor to rotate 30°. By repeating this action 12 times, the rotor will rotate.