Rotor De-Excitation via Active Rectifier Resistance Control
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Solution Overview
Problem
Externally excited synchronous machines face issues with high electrical currents or voltages induced by rotor windings, which can damage structural components, and existing de-excitation methods often require additional components for energy dissipation.
Innovation Solution
Employing an active rectifier with field effect transistors on the rotor to convert stored energy into thermal energy by controlling the transistors to form an ohmic resistance, utilizing existing components for de-excitation without additional structural elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional components are added for energy dissipation during de-excitation, then de-excitation reliability is improved, but device complexity increases
Solution Approach 1:
The rectifier circuit is designed to perform dual functions: rectification during normal operation and energy dissipation during de-excitation. By making the existing rectifier multi-functional, no additional components are required, thus improving reliability without increasing device complexity
Solution Approach 2:
The rectifier circuit serves itself by utilizing its existing structure to dissipate energy during de-excitation. The circuit uses its own components (diodes, capacitors, resistors) to convert stored electromagnetic energy into thermal energy, eliminating the need for separate protection circuits
2Ease of manufacture
If the rectifier is used for both rectification and energy dissipation, then manufacturing cost is reduced, but the rectifier's operational reliability may worsen
Solution Approach 1:
The control system activates the rectifier's energy dissipation function in advance during de-excitation sequences, preventing voltage spikes and current surges before they can damage the rectifier components. This proactive protection maintains rectifier reliability while enabling dual-function operation
Solution Approach 2:
The control system monitors the rectifier's operational state and dynamically adjusts its behavior based on feedback signals. When voltage or current thresholds are approached during de-excitation, the control system modulates the rectifier's operation to prevent overload, thus maintaining reliability while using the same components for both functions
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
Efficient and cost-effective de-excitation of rotor windings by converting stored energy into thermal energy, minimizing component damage and manufacturing effort.
Implementation Method 1
an energy stored in the rotor windings brings about an electrical current flow through the at least one field effect transistor forming the ohmic resistance, so that at least part of this energy is converted into thermal energy
Implementation Method 2
windings consisting of a conductor wire and, if appropriate, permanent magnets are provided on the part of the stator and the rotor, wherein electromagnetic interactions between the magnetic fields generated by the windings and, if appropriate, the permanent magnets bring about the generation of a drive or braking torque
Data Source
AI summary
A method for de-exciting rotor windings of a rotor of an electric machine for a motor vehicle, wherein the electric machine includes a stator and the rotor rotatably mounted with respect to the stator, wherein an active rectifier including at least one field effect transistor controllable by way of a control voltage is provided, wherein the active rectifier electrically connects a voltage source present on a part of the rotor to the rotor windings, wherein the at least one field effect transistor is brought into an operating state that de-excites the rotor windings by way of the control voltage, in which the at least one field effect transistor forms an ohmic resistance, and wherein an energy stored in the rotor windings brings about an electrical current flow through the at least one field effect transistor, and at least part of this energy is converted into thermal energy.