Inductive Rotor Energization With Free-Wheeling Fault Discharge
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Solution Overview
Problem
Inductive energization devices in electrical machines lack a free-wheeling operation capability, which is essential for safely reducing stored energy during malfunctions, due to the permanent connection between the secondary side and the rotor winding.
Innovation Solution
A power transmission device with a free-wheeling circuit that includes an electronic switching device and an electromechanical switching device to temporarily establish a conductive connection between the rotor winding and the primary side, allowing energy stored in the rotor to be rapidly and reliably injected back into the primary side during malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If an inductive energization device is used, then wear is reduced and structural space is minimized, but the capability for free-wheeling operation is lost
Solution Approach 1:
The patent applies the dynamics principle by making the connection between secondary side and rotor winding switchable rather than permanent. The free-wheeling circuit includes switching devices that can dynamically change the electrical connection state: during normal operation, the inductive connection provides wear-free power transmission, while during malfunction, the switching devices activate to create a conductive path for energy dissipation. This dynamic adaptability resolves the contradiction between maintaining wear resistance and enabling free-wheeling capability.
Solution Approach 2:
The patent introduces a free-wheeling circuit as an intermediary component between the secondary side and the rotor winding. This intermediary circuit includes switching devices and conductive paths that are not permanently connected but can be activated when needed. The intermediary enables the system to transition from pure inductive coupling to a temporary conductive connection, allowing energy to be diverted from the rotor winding without requiring permanent conductive contacts, thus maintaining wear resistance while enabling malfunction handling.
2Adaptability or versatility
If a permanent conductive connection is made between secondary side and rotor winding, then free-wheeling operation is enabled, but wear increases and structural space increases
Solution Approach 1:
The patent makes the conductive connection dynamic rather than permanent by using switching devices (such as contactors or semiconductor switches) that can open or close the circuit as needed. During normal operation, the switching devices remain open, maintaining the inductive connection without wear. When malfunction occurs, the switching devices close to create the conductive path for free-wheeling operation. This dynamic approach enables free-wheeling capability while avoiding continuous wear from permanent conductive contacts.
Solution Approach 2:
The patent implements periodic action by activating the free-wheeling circuit only during specific malfunction conditions rather than continuously. The switching devices are controlled to close temporarily when energy dissipation is needed, then open again when normal operation resumes. This periodic activation of the conductive connection provides the necessary free-wheeling capability while minimizing wear by limiting the duration of conductive contact to only when absolutely necessary.
3Reliability
If switching devices are added to enable free-wheeling operation, then malfunction handling is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the free-wheeling circuit to serve multiple functions: it can dissipate energy during malfunction, provide a controlled shutdown path, and potentially assist in regenerative braking or energy recovery scenarios. The same switching devices and circuit topology can handle various malfunction types (overcurrent, overvoltage, mechanical faults) without requiring separate dedicated circuits for each scenario. This multi-functionality improves reliability across different failure modes while limiting the increase in device complexity by using a single versatile circuit architecture.
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
Enables a free-wheeling operation in inductive power transmission systems, ensuring rapid and secure energy dissipation during malfunctions without the need for permanent conductive contacts, thus maintaining low wear and compact design.
Implementation Method 1
a primary coil which is connected to the inverter for the excitation of a primary-side magnetic field by the AC current, and wherein the secondary side comprises a secondary coil which is permeable by the primary-side magnetic field, and induces an AC current herein
Implementation Method 2
a rectifier, which is connected to the secondary coil, for electrically connecting to the rotor winding and for the rectification of the AC current which is induced by the magnetic field in the secondary coil
Data Source
AI summary
The disclosure relates to a power transmission device, including an inductive energization device for energizing a rotor winding of a rotor of the electrical machine and a free-wheeling circuit for reducing energy stored in the rotor winding during a malfunction. The energization device has a stationary primary side and a rotating secondary side. The primary side includes an inverter for connecting to a power supply device and supplying an AC current and a primary coil for the excitation of a magnetic field. The secondary side includes a secondary coil permeable by the magnetic field and a rectifier for electrically connecting to the rotor winding and rectifying the AC current induced by the magnetic field in the secondary coil. The free-wheeling circuit is configured to isolate the secondary side from the rotor winding during a malfunction and establish a conductive electrical connection between the rotor winding and the primary side.