EV Drive Assembly With Star-Delta Switching for Lower Electric Loss
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Solution Overview
Problem
Electric vehicles face limitations in extending their driving range without intermediate charging.
Innovation Solution
A drive assembly for electric vehicles that includes a battery unit with cell-level control units capable of transforming DC to AC current, allowing adjustable voltage and frequency, enabling operation in delta or star configurations to optimize phase current and voltage, thereby reducing electric losses and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the battery unit provides constant voltage only, then the system is simple, but the driving range is limited
Solution Approach 1:
The battery unit is segmented into multiple independently controllable battery cell groups, each with its own cell-level control unit. This allows different groups to be configured in different connections (series/parallel) to provide variable voltage and current, extending driving range without requiring a larger battery capacity.
Solution Approach 2:
The system dynamically reconfigures the battery cell groups between different connection modes (series for high voltage, parallel for high current) based on driving conditions. The switching means enables real-time changes in electrical configuration, allowing the battery unit to adapt its output characteristics to optimize driving range under varying load conditions.
2Loss of energy
If the three phase strands operate in delta configuration, then the power output is high, but the electric losses are increased
Solution Approach 1:
The switching means enables dynamic switching between delta and star configurations of the three phase strands. The system can operate in delta configuration when high power is needed and switch to star configuration when lower power with reduced losses is sufficient, optimizing the trade-off between power output and energy efficiency.
Solution Approach 2:
Changing the connection configuration from delta to star alters the electrical parameters (phase voltage and phase current relationships). In star configuration, the phase current is reduced by a factor of 1/√3 compared to delta configuration for the same power output, directly reducing I²R losses in the windings.
3Loss of energy
If the phase current is reduced in star configuration, then the electric losses are reduced, but the phase voltage must be increased
Solution Approach 1:
The system dynamically adjusts the battery cell group configuration to match the voltage requirements of different operating modes. When operating in star configuration with higher phase voltage, the switching means reconfigures battery cells in series to provide the necessary voltage, preventing excessive voltage stress on individual components.
Solution Approach 2:
The system changes electrical parameters by reconfiguring both the battery unit and the three-phase strands simultaneously. When switching to star configuration, the battery cells are reconfigured in series to increase output voltage, matching the higher phase voltage requirement and maintaining appropriate voltage stress levels across all 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
The drive assembly achieves increased driving range by reducing electric losses through adjustable AC current and voltage configurations, enhancing operational efficiency and extending the vehicle's range without additional charging.
Implementation Method 1
each of the cell-level control units comprises a cell-level inverter unit being configured to transform a direct current being provided by the associated battery cell or the associated group of battery cells into an alternating current (AC) of adjustable voltage
Implementation Method 2
the drive assembly comprises a switching means being electrically connected to the electric drive machine and being configured for selectively switching the three phase strands in a delta configuration or in a star configuration
Implementation Method 3
an electric drive machine with three phase strands
Data Source
AI summary
The disclosure relates to a drive assembly for an electric vehicle and to operation of a drive assembly. The drive assembly can comprise an electric drive machine with three phase strands. The drive assembly can comprise a switching means being configured for selectively switching the three phase strands in a delta configuration or in a star configuration. The drive assembly can also comprise a battery unit, wherein the battery unit comprises a plurality of battery cells and a plurality of cell-level control units. Each of the cell-level control units can be electrically connected to an associated battery cell out of the plurality of battery cells, or to an associated group of battery cells out of the plurality of battery cells, and each of the cell-level control units can comprise a cell-level inverter unit.