Electrical Machine Fault Tolerance via Phase Current Injection
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Solution Overview
Problem
Existing fault-tolerant electrical machines in gas turbine engines, aircraft, or ships face challenges when an open-circuit fault occurs in the power supply, preventing the injection of current into coils with short-circuited turns due to a lack of power from the DC or AC busbar.
Innovation Solution
The electrical machine incorporates a stator with multiple phases and a rotor of permanent magnets, equipped with power electronics that detect short circuits in coils and allow un-faulted phases to supply current to faulted phases, even if the busbar is faulty, by storing or immediately providing current to prevent overheating and further damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current is injected into a coil with a short-circuited turn using the DC or AC busbar power supply, then the magnetic flux can oppose the permanent magnets and maintain operation, but if an open-circuit fault occurs in the busbar, then current supply to the faulted coil is prevented and the system fails
Solution Approach 1:
The patent combines multiple functional capabilities into the power electronics unit. The same power electronics that normally convert power from the busbar to control coil currents are also configured to directly generate compensation currents using stored energy from DC link capacitors when busbar faults occur. This merging of normal operation and fault compensation functions into a single integrated system resolves the contradiction by maintaining reliability without adding separate complex fault supply systems.
Solution Approach 2:
The power electronics unit serves itself during busbar faults by using its own internal DC link capacitors to generate the compensation current without external power supply. The system's existing power electronics infrastructure is utilized to provide fault tolerance, eliminating the need for separate emergency power supply systems and maintaining reliability while avoiding additional complexity.
2Reliability
If the power electronics supplies current to compensate for a short-circuited turn, then the electrical machine can continue operation, but if the busbar has an open-circuit fault, then the power electronics cannot receive power to supply the compensation current
Solution Approach 1:
The DC link capacitors in the power electronics are pre-charged during normal operation to store energy. When a busbar open-circuit fault occurs, this pre-stored energy is immediately available to generate compensation currents without requiring external power supply. This preliminary energy storage enables the system to maintain reliability during power supply failures without adding continuous power consumption.
3Productivity
If all phases are used for normal power generation, then maximum efficiency is achieved, but if one phase has a short-circuited turn, then that phase cannot be used without reducing overall system performance
Solution Approach 1:
The patent converts the harmful effect of a short-circuited turn into a beneficial compensation mechanism. By detecting the short-circuited turn and injecting a specifically designed compensation current through the same power electronics, the system transforms the fault condition into an opportunity to maintain electrical output. The compensation current creates a magnetic flux that counteracts the harmful effects of the short-circuited turn, allowing the phase to remain productive rather than becoming a liability.
Solution Approach 2:
The system changes the electrical parameters (current magnitude, frequency, and phase angle) of the compensation current based on the detected short-circuit conditions. By dynamically adjusting these parameters, the power electronics can optimize the compensation effect to maintain maximum electrical output despite the phase fault, resolving the contradiction between productivity and fault tolerance.
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 solution enables continued operation by allowing un-faulted phases to supply current to faulted phases, maintaining system stability and preventing damage from excessive current flow, even during busbar disturbances or open-circuit faults.
Implementation Method 1
The magnetic flux of the current injected into the coil, or phase, has to be of such a magnitude, frequency and phase that it opposes the magnetic flux from the permanent magnets of the rotor of the electrical machine
Data Source
AI summary
An electrical machine includes a stator including a plurality of electrical phases and a rotor having a plurality of magnets. Each electrical phase includes at least one coil and power electronics. There are means to detect an electrical short circuit in a faulted coil and means to supply an electrical current to the faulted coil when an electrical short circuit is detected in the faulted coil. The means to supply the electrical current to the faulted coil includes one or more un-faulted electrical phases of the electrical machine. The un-faulted electrical phases of the electrical machine are arranged to supply the electrical current to the electrical phase containing the faulted coil. The power electronics of the un-faulted electrical phases are arranged to supply the electrical current from the un-faulted electrical phase to the power electronics of the electrical phase having the faulted coil. This overcomes a problem of a fault in the DC or AC busbar of the electrical machine.