Starter-Generator Voltage Regulation to Reduce Shock-Loading
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Solution Overview
Problem
Starter-generators in aircraft and vehicles face issues with generator shock-loading and battery shock-charging during engine start, leading to high-stress conditions for components such as batteries, contactors, and mechanical drive systems due to initial high charging currents and abrupt torque transitions.
Innovation Solution
A system and method involving a resistive voltage divider and transistor switches are used to regulate the generator output voltage by creating an error signal and filtering it to control generator field excitation, thereby reducing the initial charging current and torque load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the generator is connected to the DC power bus without charging circuitry to float-charge batteries, then the system complexity is reduced, but the initial charging current becomes excessively high causing thermal shock and battery damage
Solution Approach 1:
The patent applies preliminary action by implementing a controlled charging sequence where the generator is initially decoupled from the battery using a transfer switch. The battery is charged through a controlled path with current limiting circuitry before the generator is directly connected to the power bus, preventing thermal shock while maintaining system simplicity
Solution Approach 2:
The patent introduces intermediary components including a transfer switch and controlled charging circuitry that mediates between the generator and battery. This intermediary structure manages the charging current flow to prevent excessive initial current while maintaining overall system simplicity
2Productivity
If the line contactor closes with the battery drawing large initial recharging current, then the battery is recharged, but contact arcing occurs during contact bounce reducing contactor life
Solution Approach 1:
The patent applies preliminary action by pre-charging the battery through a controlled path before closing the line contactor. This ensures the battery voltage is接近 to the generator voltage, minimizing voltage differential and reducing arcing when the contactor closes
Solution Approach 2:
The patent implements beforehand cushioning by using a transfer switch to manage the connection timing and a controlled charging circuit to limit current during the transition period. This cushioning approach protects the contactor from high-stress arcing conditions
3Power
If the starter-generator transitions rapidly from supplying torque to drawing high torque at start-termination, then the generator meets power demand, but the abrupt load change causes mechanical stress on the accessory drive train
Solution Approach 1:
The patent applies dynamics by implementing a controlled transition sequence where the generator load is gradually increased rather than abruptly applied. The transfer switch and control circuitry manage the torque transition dynamically, reducing mechanical stress on the drive train while meeting power demands
Solution Approach 2:
The patent applies preliminary action by pre-synchronizing the generator voltage and frequency with the power bus before full load connection. This preliminary synchronization allows for a smoother torque transition and reduces mechanical shock to the drive train 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
This solution effectively mitigates the stress on battery life, contactor life, and mechanical drive components by regulating the voltage and reducing the high initial charging current and torque transitions, enhancing the reliability and longevity of these components.
Implementation Method 1
A resistive voltage divider has at least one input series resistor, a subtractor input, at least two secondary resistors, and a ground. The input series resistor is disposed between the voltage reference input and the subtractor input. The secondary resistors are disposed between the subtractor input and the ground.
Implementation Method 2
The system contains a voltage reference input positioned to be compared to an initial generator output voltage of an engine generator control unit by a subtractor circuit.
Implementation Method 3
At least two transistor switches connected between the secondary resistors and the ground.
Data Source
AI summary
The system contains a voltage reference input positioned to be compared to an initial generator output voltage of an engine generator control unit by a subtractor circuit. A resistive voltage divider has at least one input series resistor, a subtractor input, at least two secondary resistors, and a ground. The input series resistor is disposed between the voltage reference input and the subtractor input. The secondary resistors are disposed between the subtractor input and the ground. At least two transistor switches connected between the secondary resistors and the ground. The reduced generator output voltages are from the input series resistor and the secondary resistors.