Multi-Phase Drive System Rotor Overheating Protection
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Solution Overview
Problem
Permanent magnet machines (PMMs) with fixed rotor flux are prone to overheating during non-symmetrical short circuit failures, as they continue to generate electromagnetic flux until the rotor stops, posing a hazard and risk of destructive overheating.
Innovation Solution
A drive system for multi-phase electric machines with detectors on each conduction path that can convert non-symmetrical short circuit faults to symmetrical short circuit conditions, using selectable interconnection paths and a controller to connect all conduction paths, thereby converting negative sequence flux to positive sequence flux and preventing rotor overheating during continued rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a permanent magnet machine continues to generate electromagnetic flux during a short circuit, then the rotor can maintain rotation, but the rotor assembly experiences overheating and potential damage
Solution Approach 1:
The patent converts the harmful negative sequence flux into beneficial positive sequence flux by electrically interconnecting all conduction paths during a non-symmetrical short circuit fault. This transformation allows the rotor to continue rotating (benefit) while preventing the overheating that would otherwise occur from negative sequence effects (harm eliminated).
Solution Approach 2:
The patent changes the electrical configuration parameter by transitioning from individual phase conduction paths to an interconnected configuration where all conduction paths are electrically connected. This parameter change transforms the flux sequence characteristics, converting negative sequence flux to positive sequence flux and thereby preventing rotor overheating while maintaining rotation.
2Reliability
If detectors and interconnection paths are added to prevent rotor overheating, then rotor protection is improved, but device complexity increases
Solution Approach 1:
The controller is designed to perform multiple functions: normal operation control and fault detection with interconnection. By making the controller universal, the patent avoids adding separate dedicated protection devices, thereby improving rotor protection reliability while minimizing the increase in device complexity.
Solution Approach 2:
The selectable interconnection path acts as an intermediary element that is introduced only when needed during fault conditions. This mediator allows the system to maintain simple normal operation while providing complex protection functionality only when required, balancing reliability improvement with complexity management.
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
The solution effectively prevents destructive overheating of the rotor during non-symmetrical short circuit failures by converting negative sequence flux to positive sequence flux, allowing the rotor to continue rotating without overheating, as demonstrated in simulations and analyses of high-reactance PMM machines.
Implementation Method 1
A NSSCF may create negative sequence flux that may produce overheating of the rotor assembly... any negative sequence flux resulting from the fault and continued rotation of the rotor is converted to positive sequence flux
Data Source
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AI summary
A drive system for a multi-phase electric machine with a permanent magnet rotor, the drive system may comprise conduction paths for each phase. Detectors on each of the conduction paths may determine electrical condition of the conduction path. At least one selectable interconnection path may be present between all of the conduction paths. The at least one selectable interconnection path may be operable to connect all of the conduction paths together responsively to one or more of the detectors determining that the electrical condition of its respective electrical path is representative of a predetermined electrical fault condition so that heating of the rotor during continued rotation of the rotor is prevented.