Electric Vehicle On-Board Main Traction Inverter
The main traction inverter of an electric vehicle is the core of the drive system. Its function, composition and technological evolution directly affect the vehicle's performance and efficiency. The following is an in-depth analysis from three aspects: working principle, core composition and future trends.
Working Principle: Dynamic Control of Electrical Energy Conversion
Energy Conversion Principle
A H-bridge circuit is constructed using IGBT/SiC power devices to convert 400-800V high-voltage DC power into three-phase sinusoidal AC power. The space vector pulse width modulation (SVPWM) technology is adopted to dynamically control the fundamental frequency (0-400Hz) and amplitude of the output voltage, achieving precise motor speed regulation.
Vector control algorithm
The FOC (Field Oriented Control) system decouples the d-q axis currents of the motor in real time, achieving independent closed-loop control of torque and magnetic field through Clarke/Park transformation. The dynamic response time is less than 5ms, and the efficiency can reach over 98%.
Energy feedback mechanism
When regenerative braking is engaged, it switches to rectification mode. Through the boost chopper circuit, the three-phase AC power generated by the motor is rectified into DC to recharge the battery, with a maximum recovery efficiency of up to 85%.
System Architecture and Core Components
Power Hardware Layer
SiC MOSFET module: withstand voltage 1200V / current 600A, switching frequency up to 50kHz, loss reduced by 70% compared to IGBT
DC bus capacitor: uses metallized polypropylene film capacitor, capacity 400μF@800V, ESR < 5mΩ
Current sensor: closed-loop Hall element, bandwidth DC-100kHz, accuracy ±0.5%
Control unit
Multi-core MCU (such as Infineon Aurix): 200 MHz main frequency, supporting ASIL-D functional safety
Real-time operating system (AUTOSAR architecture), control cycle < 50 μs
Fault diagnosis system: covering overvoltage (> 900 V), overcurrent (± 1500 A), junction temperature (> 175 °C) and other protections
Thermal management system
Double-sided cooling structure: Thermal resistance reduced by 40%
Liquid cooling plate design: Waterway pressure drop < 20 kPa @ 10 L/min, temperature difference control < 5℃
Nanofluid coolant: Thermal conductivity increased by 30%
Technological Evolution Direction
Application of Third-generation Semiconductors
By 2025, the penetration rate of SiC inverters will exceed 60%. Trench-gate SiC MOSFETs will reduce on-resistance to 2 mΩ·cm². Combined with silver sintering packaging technology, the module power density will exceed 50 kW/L.
The domain controller integrates the inverter, on-board charger (OBC), and DC/DC converter. It adopts copper pillar interconnection technology, reducing the system volume by 40% and the wiring harness by 70%.
Intelligent predictive control
Based on the digital twin model of the motor, deep learning algorithms are applied to predict load changes and adjust the switching sequence in advance, expanding the flat efficiency curve area by 15%.Wireless power transmission
The resonant wireless charging system is integrated with inverter topology to achieve high-frequency inversion at 85kHz, with a transmission efficiency of over 93%, supporting dynamic charging scenarios.
Functional safety upgrade
Compliant with ISO 21434 cybersecurity standards, equipped with a hardware encryption module (HSM), supports OTA remote refresh of control strategies, and has a fault prediction accuracy rate of over 95%.
Currently, the BMW iX M60 has achieved a co-shell design for the inverter and motor, reducing weight by 30%. The Tesla Model S Plaid uses a silicon carbide inverter, which has increased its range by 6%. In the future, as the 800V platform becomes more widespread, a GaN+SiC hybrid topology may become a new direction, with the switching frequency expected to exceed 200kHz, driving the drive system towards higher power density.
SMC, as a globally leading power semiconductor device manufacturer with nearly 30 years of history, can provide customers with the most advanced, efficient, and cost-effective third-generation silicon carbide MOSFETs and silicon carbide JBS diodes. In addition, SMC has unique experience in silicon-based power diode devices, and its best-selling high-power ultra-fast recovery diodes, high current Schottky diodes, and other products are highly praised by customers worldwide. SMC's power semiconductor devices can provide higher efficiency, better reliability, good delivery time, and competitive prices for your products. SMC's professional service team around the world allows you to experience the ultimate customer service experience and safeguard your product design.
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