Variable-Voltage Vehicle Alternator for Low-RPM 12V/48V Charging
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Solution Overview
Problem
High voltage alternators, such as 48 volt systems, do not provide sufficient battery charging at low engine speeds, while 12 volt systems offer good cut in speeds but are large and heavy, and existing dual alternator systems are not ideal for space-constrained vehicles.
Innovation Solution
A variable voltage charging system that allows a single alternator to operate in both 12 volt and 48 volt modes, switching between low and high voltage outputs based on engine speed to utilize the benefits of both systems, with a controller managing the alternator and switch to ensure efficient charging and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high voltage alternator (48V) is used, then the maximum charge output is improved and wire size is reduced, but the charging performance at low engine speeds deteriorates
Solution Approach 1:
The alternator system dynamically switches between 48V high voltage mode for maximum power output at high engine speeds and 12V low voltage mode for effective charging at low engine speeds. The controller monitors engine speed and automatically adjusts the operating voltage, enabling the single alternator to adapt its characteristics to match the charging requirements at different operational conditions.
2Adaptability or versatility
If a single pole breaker is inserted in the auxiliary battery system circuit, then the dual mode charging system is provided, but the device complexity increases with additional switching components
Solution Approach 1:
The single alternator is designed to perform multiple functions by operating in both 48V high voltage mode and 12V low voltage mode. The system uses a controller with engine speed sensing capability that automatically determines the appropriate operating mode, eliminating the need for separate alternators while providing dual-mode charging versatility.
3Speed
If a 12V alternator system is used, then the cut in speed is improved, but the weight and size of the system increase
Solution Approach 1:
A single alternator system is designed to operate in both 48V and 12V modes, combining the advantages of both systems. The 48V mode provides high power output with reduced weight and size, while the 12V mode delivers excellent low-speed cut-in performance. The controller automatically selects the appropriate mode based on engine speed, eliminating the need for separate heavy 12V alternator systems.
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 system provides efficient charging at low engine speeds and high engine speeds, reducing heat generation and wire size, while maintaining the high maximum charge output of higher voltage systems and the low cut in speed of 12 volt systems, thus enhancing the viability of high voltage systems.
Implementation Method 1
an alternator configured to generate electric power from a rotation output of an engine
Data Source
AI summary
A charging system for a vehicle includes an alternator configured to alternately output at least a low charge voltage to charge a low voltage storage device and a high charge voltage to charge a high voltage storage device, and a switch configured to switch between at least a first switch position connecting the alternator to the low voltage storage device and a second switch position connecting the alternator to the high voltage storage device. A controller is configured to control operation of the alternator and the switch between at least a low voltage mode and a high voltage mode based on at least one of an engine RPM and a temperature. In the low voltage mode the alternator outputs the low charge voltage and the switch is in the first switch position and in the high voltage mode the alternator outputs the high charge voltage and the switch is in the second switch position.