How to Choose the Suitable Motor for the Electrification Conversion of Wuling Rongguang Mini Bus?(336V, 2-in-1 PMSM, Liquid-Cooled, 9000RPM, 220N·m)
Electrifying the Wuling Rongguang mini bus requires a carefully selected electric motor system that balances performance, efficiency, durability, and compatibility. Given the target specifications—336V voltage platform, 2-in-1 motor-controller integration, Permanent Magnet Synchronous Motor (PMSM), liquid cooling, maximum speed of 9000RPM, and peak torque of 220N·m—choosing the right motor is crucial to achieving reliable and efficient operation. Here’s a comprehensive guide to making the optimal choice.
- Match Voltage and Power Requirements
The motor must operate on a 336V DC nominal voltage, aligning closely with the 385V platform of the reference 120kW powertrain. Since the operating range is 290V–480V, a 336V system ensures compatibility and stable performance. Confirm that the motor and integrated controller can handle voltage fluctuations without compromising efficiency or safety.
- Select the Right Motor Type: PMSM for High Efficiency
Permanent Magnet Synchronous Motors (PMSM) are ideal for mini buses due to their high efficiency (≥92%), excellent power density, and smooth torque delivery. PMSM motors offer superior control across a wide speed range, making them suitable for urban driving with frequent stops and starts. Ensure the motor uses neodymium magnets for strong magnetic fields and long-term performance.
- Performance: Speed and Torque Matching
The target motor should reach a maximum speed of 9000RPM, lower than the 15,000RPM in the reference, indicating a more conservative, durable design suited for city driving. The peak torque of 220N·m must be sustained for at least 10–30 seconds to handle acceleration and hill climbing. Verify that the motor delivers sufficient rated torque (e.g., ≥100N·m) for continuous operation without overheating.
- Integrated 2-in-1 Design: Motor + Controller
A 2-in-1 integrated motor and controller setup reduces space, weight, and wiring complexity—critical for compact vehicles like the Rongguang mini bus. Ensure the controller supports vector control (FOC) for precise torque and speed regulation. The integrated unit should include protections for overcurrent, overvoltage, and thermal shutdown, with a peak current rating of at least 400A.
- Liquid Cooling for Thermal Management
Given the liquid-cooled requirement, the motor must have a jacket or internal cooling channels for circulating coolant. This is essential for sustained high-load operation, especially in hot climates or hilly terrain. Proper thermal management prevents demagnetization of permanent magnets and extends motor life. Confirm compatibility with common EV coolants and integration into the vehicle’s cooling loop.
- Design Life: 25 Years or 100,000 km
Although the reference powertrain is rated for 20 years/300,000 km, the target design life here is 25 years or 100,000 km, emphasizing longevity over high mileage. This suggests a focus on reliability and low maintenance. Choose a motor with H-class insulation (withstands 180°C), sealed bearings, and corrosion-resistant materials. The IP67 protection rating ensures dust and water resistance, critical for real-world conditions.
- Efficiency and Energy Savings
High system efficiency (≥92%) reduces energy consumption and extends battery range. Look for motors with low copper and iron losses, optimized windings, and regenerative braking support. The motor should efficiently convert electrical energy into mechanical power across a wide operating range, especially at low to medium speeds common in urban driving.
- Mechanical Integration and Mounting
Ensure the motor’s mounting dimensions, flange type, and shaft output match the existing transmission or reduction gearbox. If using a separate gearbox, confirm the center distance (e.g., 180mm) and reduction ratio (e.g., ~10:1) to achieve desired wheel speed and torque. A mechanical differential is recommended for balanced traction.
- Sensors and Control Feedback
The motor must include a resolver or high-resolution encoder for precise rotor position feedback, essential for FOC. A PT1000 temperature sensor should monitor internal winding temperature in real time, enabling the BMS and controller to adjust output and prevent overheating.
- Safety and Compliance
The motor system must comply with automotive safety standards (e.g., ISO 6469, IEC 60529). Features like insulation monitoring, emergency power cutoff, and high-voltage interlock (HVIL) are essential. The controller should support CAN communication (CAN 2.0B) for integration with the vehicle’s BMS, dashboard, and charging system.
Conclusion
Choosing the right motor for the Wuling Rongguang mini bus conversion means selecting a 336V, liquid-cooled, 2-in-1 PMSM motor that delivers 220N·m of torque and 9000RPM max speed, with high efficiency, robust thermal management, and a design life of 25 years. By prioritizing integration, reliability, and safety, and referencing proven designs like the 120kW 3-in-1 powertrain, you can achieve a durable, efficient, and high-performing electric mini bus suitable for long-term urban transportation needs.
