Dual-Motor Propulsion Coupling for Galvanically Isolated Charging
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Solution Overview
Problem
Existing electric propulsion systems for vehicles face challenges in balancing cost, component weight, and dimensions while maintaining efficient and safe galvanic isolation during charging and propulsion, especially when using conductive electric road systems without protective earth connections.
Innovation Solution
An electric propulsion system with dual electrical machines and an electrically isolated coupling assembly, allowing for galvanic isolation and flexible operational modes, including traction, charging, and power transfer between machines and external power sources, using bidirectional converters and a switch assembly for efficient power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolation is provided between external electrical supply network and onboard batteries, then safety is improved, but device complexity increases
Solution Approach 1:
The electrical machine serves multiple functions: it acts as a motor during propulsion and as a generator during regenerative braking, while also enabling galvanic isolation during charging operations. This multi-functionality reduces the need for separate isolation devices, thereby maintaining safety without proportionally increasing device complexity.
Solution Approach 2:
The electrical machine functions as an intermediary component between the external electrical supply network and the onboard battery pack assembly. During charging, the machine provides galvanic isolation while still allowing power transfer, thus achieving safety requirements without adding dedicated isolation hardware that would increase complexity.
2Reliability
If two separate multi-phase bridge inverters are used for galvanic isolated charging, then galvanic isolation is achieved, but device complexity and cost increase
Solution Approach 1:
A single multi-phase bridge inverter is designed to handle multiple operational modes including propulsion, regenerative braking, and charging with galvanic isolation. This eliminates the need for two separate inverters while maintaining the galvanic isolation capability, thereby reducing device complexity and cost.
Solution Approach 2:
The patent combines the functions of propulsion inverter and charging inverter into a single multi-phase bridge inverter system. By merging these functions, the system achieves galvanic isolated charging without requiring duplicate inverter hardware, thus reducing overall device complexity.
3Adaptability or versatility
If dual electrical machines are used for flexible operational modes, then adaptability is improved, but weight and dimensions increase
Solution Approach 1:
Each electrical machine is designed to perform multiple functions including motor operation for propulsion, generator operation for regenerative braking, and isolation function during charging. This multi-functionality allows the system to achieve operational flexibility with machines that are not oversized for single purposes, thereby controlling weight and dimensions.
4Adaptability or versatility
If switch assembly is used for connecting electrical machines to energy storage system or external power source, then adaptability is improved, but device complexity increases
Solution Approach 1:
The switch assembly is integrated with the multi-phase bridge inverter system to provide operational mode switching between propulsion, regenerative braking, and charging modes. By combining the switching function with the existing inverter structure, the system achieves adaptability without proportionally increasing device 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
Enables safe and efficient power transfer and charging from both static and conductive electric power sources, supporting multi-axle drive and torque-vectoring, while maintaining isolation and optimizing system efficiency and safety.
Implementation Method 1
a first bidirectional DC/AC converter disposed in a first electrical connection extending from the first electrical machine; a second bidirectional DC/AC converter disposed in a second electrical connection extending from the second electrical machine
Data Source
Figure 1
Figure 2
Figure 3a
AI summary
The invention relates to an electric propulsion system (100) for a vehicle (1), said system comprising a first electrical machine (12) and a second electrical machine (14) for providing propulsion to said vehicle, characterized in that said system further comprises an electrically isolated coupling assembly (20) configured to provide electrical isolation between said first and said second electrical machines; a first bidirectional DC/AC converter (68) disposed in a first electrical connection (82) extending from the first electrical machine; a second bidirectional DC/AC converter (69) disposed in a second electrical connection (84) extending from the second electrical machine; a switch assembly (30) connected via at least one of the bidirectional DC/AC converters to at least one of the first and second electrical machines and further connected to an onboard energy storage system (40); and wherein said switch assembly is configured to connect at least one of the first electrical machine and the second electrical machine to either the onboard energy storage system (40) or to an externally supplied power source (50, 90), thereby said switch assembly being configured to set the electric propulsion system in a number of operational modes.