EV Motor Rotor Positioning for Parked Battery Heating
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Solution Overview
Problem
Electric vehicle traction batteries experience performance degradation in cold temperatures, especially when parked, due to inefficient heating methods.
Innovation Solution
A system and method that utilize the electric machine's rotor to rotate the vehicle's wheel when parked, allowing the electric machine to be controlled to inject d-axis current for heating the traction battery by adjusting the rotor position to maximize current flow through monitored phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a battery heater is used to heat the battery in cold temperatures, then the battery temperature is improved, but the energy consumption and system complexity increase
Solution Approach 1:
The electric machine serves dual purposes: propulsion during vehicle operation and battery heating when parked. By injecting d-axis current into the stator windings, the electric machine generates heat internally through resistive heating (I²R losses), eliminating the need for a separate battery heater system. This self-service approach reduces energy consumption and system complexity while effectively heating the battery in cold temperatures.
2Productivity
If the rotor is rotated to preset positions to optimize current flow, then the heating efficiency is improved, but the control complexity increases
Solution Approach 1:
The controller pre-determines optimal rotor positions (preset positions) that correspond to specific stator phases. By rotating the rotor to these predetermined positions before injecting d-axis current, the system ensures maximum current flow through the desired phase windings, optimizing heating efficiency. This preliminary positioning action simplifies the control logic compared to real-time optimization algorithms.
3Temperature
If the vehicle wheel is rotated through the electric machine, then the battery heating is achieved, but the mechanical wear and potential safety issues increase
Solution Approach 1:
Instead of using a purely mechanical heating system or directly engaging the wheel rotation mechanism for heating, the invention substitutes by using electrical current injection (d-axis current) into the electric machine's stator windings. This electrical approach generates heat through resistive heating without requiring mechanical wheel rotation or engagement, thereby eliminating mechanical wear and potential safety issues associated with moving the vehicle or rotating wheels solely for heating purposes.
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
Effectively heats the traction battery in cold conditions by optimizing current flow through the battery, thereby improving battery performance and vehicle readiness.
Implementation Method 1
the electric machine to be controlled to inject d-axis current for heating the traction battery by adjusting the rotor position to maximize current flow through monitored phases
Data Source
AI summary
A vehicle includes an electric machine including a rotor. The vehicle further includes a traction battery configured to supply electric power to the electric machine. The vehicle further includes a wheel mechanically coupled to the electric machine. The vehicle further includes one or more controllers programmed to, responsive to detecting a battery temperature below a threshold and the vehicle being parked, rotate the rotor to a preset position such that the wheel rotates.