Electric Vehicle Torque Redistribution for Thermal Protection
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Solution Overview
Problem
Electric vehicles equipped with synchronous motors and inverters experience drivability issues and thermal problems when the inverter enters a locked state, leading to increased temperature and reduced torque, causing the vehicle to stop mid-slope on inclines.
Innovation Solution
The integration of a control unit with a torque varying device that adjusts the output torque from the synchronous motor while maintaining total drive force by increasing the output torque from an induction motor when the vehicle is stopped, thereby preventing drivability deterioration and thermal protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the phase angle of the current is changed to avoid a specific switching element being in the ON state, then the temperature increase of the switching element is restrained, but the angle of rotation of the synchronous motor changes irrespective of the operation of the accelerator pedal, causing the electric vehicle to swing in the fore-and-aft direction and deteriorating drivability
Solution Approach 1:
The system dynamically switches between two control strategies based on the operating state: normally operating the synchronous motor with standard phase angle control for smooth drivability, and detecting locked state conditions to switch to induction motor operation with adjusted phase angles for thermal protection, thus adapting to different operational requirements
Solution Approach 2:
The induction motor serves as an intermediary solution when the synchronous motor enters a locked state. By switching to the induction motor with adjusted current phase angles, the system achieves thermal protection of the inverter while maintaining vehicle propulsion capability
2Temperature
If the current of the switching element is lowered when the inverter is brought into the locked state, then the temperature increase is reduced, but the output torque from the motor is lowered, causing the vehicle to slip down on a sloping road and deteriorating drivability
Solution Approach 1:
The system creates a functional copy by switching from the synchronous motor to the induction motor when the synchronous motor's inverter is in a locked state. The induction motor replicates the torque-producing function while allowing different current control strategies that prevent inverter overheating
Solution Approach 2:
The system changes the operating parameters by switching motor types and adjusting current phase angles. When the synchronous motor cannot operate safely due to locked state, the induction motor operates with optimized phase angles to maintain torque while protecting the inverter from thermal damage
3Productivity
If the synchronous motor is used to drive the vehicle, then the vehicle can operate normally, but the inverter may enter a locked state causing increased temperature and reduced torque
Solution Approach 1:
The system implements dynamic monitoring and switching capability, continuously detecting locked state conditions in the synchronous motor's inverter and dynamically switching to the induction motor when thermal protection is needed, thus maintaining both productivity and reliability
Solution Approach 2:
The system prepares a backup propulsion solution by having the induction motor ready to operate when the synchronous motor's inverter enters a locked state. This preemptive arrangement ensures continuous vehicle operation while protecting the inverter from thermal damage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively maintains drivability and prevents thermal damage to motor components by redistributing torque from the synchronous motor to the induction motor, ensuring smooth operation and reducing overheating risks.
Implementation Method 1
a synchronous motor for driving a vehicle
Implementation Method 2
an induction motor for driving the vehicle
Data Source
AI summary
An electric vehicle includes: a synchronous motor; an induction motor; and a control unit configured to adjust a torque from the synchronous motor and a torque from the induction motor, wherein the control unit includes a torque varying device configured to reduce an output torque from the synchronous motor while maintaining a total drive force of the electric vehicle, and increasing an output torque from the induction motor in the case where the electric vehicle is stopped in a state in which a torque is output from the synchronous motor. Accordingly, there is provided an electric vehicle capable of restraining deterioration of drivability and performing thermal protection of a motor and a control unit.