How Do the Three Core Components: Motor, Controller and Reducer Work?
An electric drive system is not a single component, but a collaboration of three key modules:
Traction Motor – Converts electrical energy into mechanical energy. Permanent magnet synchronous motors (PMSM) are the mainstream choice, featuring high efficiency, compact size and superior power density, and are widely deployed in passenger vehicles. The motor can reach speeds of 15,000–20,000 rpm.
Motor Control Unit (MCU / Inverter) – Converts direct current from the traction battery into three-phase alternating current required by the motor. It adjusts voltage and frequency in real time according to accelerator pedal signals to regulate motor speed and torque. Its core power devices are IGBT modules or silicon carbide MOSFETs (used in high-end models).
Reducer – Reduces the motor's high rotational speed while amplifying torque, and transmits power to the wheels to propel the vehicle. It is the equivalent of the transmission in gasoline vehicles, yet with a simpler structure and higher efficiency.
For example: When you press the accelerator pedal, the MCU receives the signal and converts the battery's DC power into three-phase AC within milliseconds. The motor spins up to 15,000 rpm; the reducer then drops the speed to around 1,000 rpm before power reaches the wheels. The whole process is several times faster than the throttle-to-wheel response of internal combustion engine vehicles.
Workflow and Energy Regeneration: How Does the EV Move and Save Power?
The workflow of an electric drive system works like an efficient "command chain":
The Vehicle Control Unit (VCU) interprets the driver's intention for acceleration or braking, calculates the required torque and sends out commands.
The MCU controls the inverter to receive VCU commands, converts direct current into alternating current and drives the motor to rotate.
Closed-loop energy flow: The motor drives the wheels through the transmission mechanism.
During deceleration, the motor works in reverse to generate electricity, recovering kinetic energy into the battery and improving energy utilisation.
The core of this process lies in energy regeneration. When you lift off the accelerator or hit the brake, the motor switches to generator mode, converting the vehicle's kinetic energy back into electricity and storing it in the battery. Industry data shows energy regeneration can extend driving range by 15%~25% under urban driving cycles. As cited in the Weibo account of Huazhong Advanced Vocational and Technical School, this is the so‑called "closed-loop energy flow".