Redundant Electric Machine Windings with Current Limiting
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Solution Overview
Problem
Existing electric machines with permanent magnet windings lack redundancy and effective current limiting mechanisms, leading to potential thermal damage and loss of functionality during short circuit conditions, as prior art methods do not provide sufficient magnetic and electrical isolation or redundancy.
Innovation Solution
The electric machine incorporates a stator assembly with windings disposed around teeth, where each phase includes pairs of coils wrapped in opposite directions to induce mutual inductance, providing both magnetic and electrical isolation, and a method where coils in the same phase are arranged to flow current in the same direction during faults, increasing total impedance and limiting short circuit currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If magnetic material is used to stop flux circulation above a certain temperature, then the operating temperature of the windings is limited and overheating is prevented, but the machine stops working until it cools down
Solution Approach 1:
The winding system is segmented into multiple independent parallel paths. When thermal protection is activated in one path due to overheating, only that specific path stops working while other paths continue to operate. This maintains partial power output during fault conditions, resolving the contradiction between temperature control and productivity.
Solution Approach 2:
The system changes operational parameters by switching from a single-phase full-power mode to a reduced-phase partial-power mode when faults occur. This parameter change allows the machine to continue operating at reduced capacity rather than completely shutting down, balancing temperature protection with productivity maintenance.
2Object-affected harmful factors
If leakage flux and leak impedance are used to limit maximum current, then the inductance is increased and current is limited, but winding redundancy is not provided
Solution Approach 1:
The winding is segmented into multiple independent parallel paths with current limiting means in each path. This segmentation provides both current limitation (through the leak impedance in each path) and redundancy (since failed paths do not affect other paths). The contradiction is resolved by applying segmentation to enable both functions simultaneously.
Solution Approach 2:
The patent merges two separate functions (current limitation and redundancy provision) into a single integrated winding architecture. By combining multiple parallel paths with current limiting means in each path, the system achieves both maximum current limitation and winding redundancy, resolving the contradiction between these two features.
3Reliability
If coils are arranged to induce mutual inductance, then magnetic and electrical isolation is provided between phases, but device complexity increases
Solution Approach 1:
The winding system is segmented into independently controllable phases with magnetic and electrical isolation between them. Each phase can be independently protected and controlled through current limiting means. This segmentation provides the isolation needed for reliability while the modular nature of the segmentation keeps the complexity manageable through standardization.
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 configuration allows the machine to operate at reduced capacity during and after short circuit conditions, preventing thermal damage and maintaining electrical output by ensuring magnetic and electrical isolation of phases, thus enhancing redundancy and reliability.
Implementation Method 1
each phase includes at least one pair of coils wrapped in opposite directions around adjacent teeth to induce mutual inductance between the coils
Implementation Method 2
A total impedance of the phase may be sufficiently high such that a short circuit current in the phase of the windings is limited to a current magnitude below that at which thermal damage is caused to the electric machine
Implementation Method 3
The coils of different phases may be magnetically and electrically isolated to provide winding redundancy
Data Source
AI summary
An electric machine comprises a rotor assembly and a stator assembly adjacent the rotor assembly. The stator assembly includes windings disposed around a plurality of teeth, with each phase of the winding including at least one pair of coils wrapped in opposite directions around adjacent teeth to induce mutual inductance between the coils when electrical current flows through the phase of the winding. The coils of different phases are be arranged to cancel magnetic coupling between the different phases. The winding arrangement provides a way to accomplish multiple, redundant, magnetically and electrically isolated windings with current limiting means in a single stator of an electric machine. The winding arrangements inherently provide an increase in mutual inductance and, therefore, an increase in impedance over that possible with prior art winding arrangements to limit the maximum short circuit current in the windings.