Separately Excited Generator Holding Current Control
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Solution Overview
Problem
In motor vehicles, starter generators experience delays in reaching nominal current intensity due to high rotor winding inductance, which slows down engine starting and causes unwanted voltage dips during switchover from standby to operational modes.
Innovation Solution
Maintaining a holding current intensity greater than zero in the rotor winding during idling and using pulse-width modulated voltage signals with reduced pulse duty factors to rapidly reach nominal current intensity, allowing for quicker engine starting and reduced switchover times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pulse-width modulated voltage signal with 100% pulse duty factor is used to activate the exciting coil, then nominal current intensity is achieved, but it takes considerable time (e.g., 300 ms) due to high rotor winding inductance
Solution Approach 1:
The patent applies preliminary action by maintaining a holding current (greater than zero but less than nominal current) in the rotor winding during idling phases before regenerative or motive operation is required. This preliminary current presence allows the exciting coil to reach nominal current intensity much faster when operation is needed, reducing the time delay from 300 ms to a significantly shorter duration while avoiding complete current shutdown during standby
Solution Approach 2:
The patent uses periodic action through pulse-width modulated voltage signals with reduced pulse duty factors during idling phases to maintain a holding current in the rotor winding. This periodic excitation keeps the magnetic field partially active, enabling rapid transition to full power operation when needed, thus resolving the time delay issue without continuous full-power consumption
2Use of energy by moving object
If exciting current is completely switched off during standby to save energy, then energy consumption is reduced, but switching back to operational mode causes voltage dips and delays engine starting
Solution Approach 1:
The patent maintains a holding current in the rotor winding during standby phases instead of completely switching off the exciting current. This preliminary current maintenance ensures that when the generator needs to be activated, the transition is smooth and rapid, preventing voltage dips in the vehicle electrical system and ensuring reliable engine starting without the harmful effects of complete current shutdown
Solution Approach 2:
The patent applies partial action by maintaining a holding current that is greater than zero but less than the full nominal current during standby. This partial current maintenance strikes a balance between energy conservation and system readiness, providing enough magnetic field strength to enable rapid switchover to full power operation while consuming less energy than continuous full-power operation
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 approach shortens engine starting time and reduces voltage dips by allowing the electric machine to reach nominal current intensity more quickly and maintain power delivery with reduced thermal loading, preventing rotor winding overload.
Implementation Method 1
the exciting current through the rotor winding of an electric machine in a motor vehicle
Implementation Method 2
the exciting current may be set using a pulse-width modulated voltage signal, where in the case of continuous activation (thus, a pulse duty factor or pulse duty factor of the voltage signal of 100% or 1), an exciting current having a nominal current intensity flows
Data Source
AI summary
A method for operating a separately excited electric machine, in particular, a generator of a motor vehicle, where an exciting current flows through a rotor winding of the electric machine at a nominal current intensity during a normal operation and at a holding current intensity in an idling operation; the holding current intensity being greater than zero and less than the nominal current intensity.