Electric Axle Inverter Control for Uniform Phase Heating at Standstill
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Solution Overview
Problem
Existing electric vehicle systems face uneven thermal loading of individual phases in electric machines, leading to impaired functionality and reduced lifespan due to asymmetrical heating during heat generation.
Innovation Solution
A method and apparatus for controlling an electric machine in a partially electrified vehicle to uniformly thermally load the phases by adjusting phase currents using a converter device with semiconductor-based power switches, ensuring symmetrical thermal loading and efficient heat generation without additional heating sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If phase currents are fed into the electric machine to generate heat, then heat is generated for vehicle components, but the individual phases are not uniformly heated leading to asymmetrical thermal load
Solution Approach 1:
The control method applies different current magnitudes to different phases based on their individual thermal states. The controller determines which phases require heating and applies current preferentially to those phases, creating non-uniform current distribution that results in uniform thermal loading across all phases. This local quality adjustment resolves the asymmetrical heating problem while maintaining reliability.
Solution Approach 2:
The system dynamically changes the current parameters (magnitude and distribution) across different phases based on real-time thermal conditions. By monitoring thermal states and adjusting current parameters accordingly, the system achieves uniform thermal loading while preventing asymmetrical thermal stress that would compromise reliability.
2Temperature
If additional heating sources are added to the vehicle system, then heat requirement can be met, but device complexity increases
Solution Approach 1:
The electric machine serves dual functions: propulsion during vehicle operation and heat generation during standstill. By utilizing the existing motor windings and inverter for heating purposes, the system meets heat requirements without adding separate heating sources. This multi-functionality approach reduces device complexity while ensuring temperature requirements are satisfied.
Solution Approach 2:
The electric machine provides its own heating capability by converting electrical energy to thermal energy through controlled current application. The system uses its existing components (motor windings, inverter, controller) to generate heat, eliminating the need for external heating sources and reducing overall system complexity.
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
Uniform thermal loading of electric machine phases enhances functionality and extends service life while optimizing energy use, allowing heat generation for vehicle components like the battery without overheating or unnecessary energy consumption.
Implementation Method 1
When the two power switches are alternately opened and closed with a predetermined duty cycle, such as according to a pulse width modulation, the desired phase voltage, particularly sinusoidal phase voltage, appears at the phase
Implementation Method 2
During operation of the electric machine, copper losses can occur on the machine side and switching losses can occur on the inverter side
Implementation Method 3
conduction losses can occur on the inverter side
Implementation Method 4
These phase voltages generate a rotating stator magnetic field which interacts with the magnetic field of the rotor and accordingly drives the rotor in rotational motion
Data Source
AI summary
A method for controlling an electric machine of an electric axle drive system in an at least partially electrified vehicle. The electric axle drive system has a converter device, particularly an inverter unit, upstream of the electric machine for voltage conversion. The method detects a standstill of the vehicle; receives a heat requirement signal of the vehicle which is at a standstill, which heat requirement signal indicates a heat requirement of at least one vehicle component of the vehicle; actuates the converter device, particularly the inverter unit to energize the electric machine such that a difference between a predefined reference value and an actual value of a total thermal load lies below a predefined threshold, and a thermal load difference between the individual phases of the electric axle drive system is minimized.