Drive Axle Torque Derating Using Inverter and Motor Temperatures
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Solution Overview
Problem
Existing drive axle systems for electric vehicles lack effective temperature-based control mechanisms to manage torque output, leading to potential overheating and reduced performance due to inadequate derating strategies that consider inverter, stator, and rotor temperatures.
Innovation Solution
A method and system that determine torque commands based on the temperatures of the inverter, stator, and rotor, limiting peak and continuous torque by applying derating values when temperature thresholds are exceeded, with nonlinear derating as temperatures increase, to prevent overheating and maintain optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If torque output is increased to improve vehicle performance, then power and speed are improved, but temperature of inverter, stator, and rotor increases leading to overheating
Solution Approach 1:
The control system continuously monitors temperatures of the inverter, stator, and rotor, and uses this feedback to dynamically adjust torque commands. When temperature thresholds are exceeded, the system automatically reduces torque output to prevent overheating, creating a closed-loop control mechanism that balances performance with thermal management.
Solution Approach 2:
The torque command is made dynamic rather than static, adjusting in real-time based on temperature conditions. The system transitions between different torque levels (peak torque, continuous torque, derated torque) depending on the thermal state of critical components, allowing optimal performance when cool and protective reduction when hot.
2Temperature
If derating is applied to reduce temperature, then temperature is controlled, but torque output and vehicle performance are reduced
Solution Approach 1:
The system changes the torque parameter dynamically based on temperature conditions. Instead of applying a fixed derating, the torque command is adjusted as a variable parameter that responds to thermal conditions, allowing full torque when temperatures are acceptable and reduced torque only when necessary to manage heat.
Solution Approach 2:
The system applies derating only partially and only when necessary. Rather than continuously limiting torque, the system applies full peak torque when temperature thresholds are not exceeded and applies derating only when temperature limits are approached, using the minimum necessary action to control temperature.
3Temperature
If peak torque is limited to prevent overheating, then temperature control is improved, but vehicle acceleration and dynamic performance are worsened
Solution Approach 1:
The system allows periodic or temporary use of peak torque when temperature conditions permit, interspersed with derated operation when temperatures rise. This periodic alternation between full performance and thermal management modes maintains acceleration capability while preventing sustained overheating.
Data Source
AI summary
A drive axle system and a method of control. A control system determines a torque command based on an inverter temperature, a stator temperature of a stator of an electric motor, and a rotor temperature of a rotor of the electric motor. The electric motor is operated to provide torque based on the torque command.