Traction Motor Winding Reconfiguration to Limit Back-EMF
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Solution Overview
Problem
Existing electric vehicle traction systems face challenges in ensuring safety due to the risk of uncontrolled generator operations, which can lead to sudden braking, especially when the drive inverter is disconnected. This requires complex and costly active safety strategies to prevent energy recirculation between the inverter and electric machine.
Innovation Solution
The system employs a switching device to reconfigure the stator windings of the electric machine between low-speed and high-speed configurations. The high-speed configuration ensures that the induced voltages never exceed the battery voltage, eliminating the risk of uncontrolled generator operations without the need for active safety strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an active safety strategy (active short circuit) is implemented to prevent uncontrolled generator operations, then safety and reliability are improved, but device complexity and product costs increase significantly
Solution Approach 1:
The inverter is switched off in advance, before the electric machine enters the uncontrolled generator operation area. By proactively preventing the machine from reaching the hazardous operating condition rather than reacting to it, the need for complex active short circuit safety systems is eliminated while maintaining reliability
Solution Approach 2:
The harmful function of the active safety strategy (active short circuit) is extracted and replaced by a simpler control approach. Instead of implementing complex hardware-based short circuit protection, the solution removes the problem at its source by controlling the inverter shutdown timing
2Adaptability or versatility
If the inverter is disconnected to allow electric machine reconfiguration, then adaptability is improved, but the risk of uncontrolled generator operations increases
Solution Approach 1:
The inverter is switched off before the reconfiguration process begins, eliminating the risk of uncontrolled generator operations during the transition. This preliminary action ensures that the electric machine cannot enter hazardous operating conditions while the stator windings are being reconfigured
Solution Approach 2:
The control unit acts as an intermediary that coordinates the inverter shutdown and reconfiguration timing. It manages the transition process to ensure safety while enabling the adaptability benefits of reconfiguration
3Reliability
If robust components and redundant branches are implemented to withstand all conditions, then reliability is improved, but product complexity and costs increase
Solution Approach 1:
The need for robust components and redundant branches is extracted and eliminated by changing the control strategy. Instead of designing hardware to withstand extreme conditions, the solution prevents those conditions from occurring through proactive inverter shutdown
Solution Approach 2:
The control system serves itself by managing safety through intelligent control rather than relying on hardware redundancy. The system uses its own control capabilities to prevent hazardous conditions, eliminating the need for additional robust components
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 approach simplifies the system architecture, reduces costs, and enhances safety and reliability by eliminating the need for active safety systems, while maintaining high performance and a wide operating range.
Implementation Method 1
the voltages induced by the rotation of the rotor of the electric machine (back electromotive force—BEMF)
Data Source
AI summary
An electric or hybrid electric-endothermic traction system comprises an electric machine, an inverter, a battery, and a switching device configured to switch between a low-speed configuration, in which the stator windings assume a first electric configuration, and a high-speed configuration, in which the stator windings assume a second electric configuration, wherein the first electric configuration results in a voltage induced by the rotation of the rotor that, on reaching a pre-determined threshold value of the angular velocity of the rotor, exceeds a supply voltage of the battery, whereas the second electric configuration of the stator windings results in a voltage induced by the rotation of the rotor that is lower than the voltage of the battery for any angular velocity within a range of use of the machine. An emergency device is connected to the switching device, control unit and/or inverter.