Dual Star Winding Circuit for Fast Short-Circuit Detection
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Solution Overview
Problem
In electric machines, particularly those with a permanently excited rotor, short circuits between tooth windings can induce large electrical currents, leading to thermal destruction and damage, especially in critical applications like aircraft, due to the inability to accurately detect and respond to such faults in a timely manner.
Innovation Solution
An electrical system with two star circuits and a measuring device connected between them allows for improved detection of short circuits by measuring electrical variables, enhancing signal-to-noise ratio and reducing latency, enabling faster countermeasures such as stopping the machine or activating cooling, and includes an inverter unit for modulating signals to optimize detection at low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single star circuit is used with conventional measurement, then the construction is simpler, but the measurement precision is insufficient due to interference from magnetic saturation and external components
Solution Approach 1:
The electrical system is segmented into two independent star circuits (first star circuit and second star circuit) that are electrically isolated from each other. Each star circuit has its own measuring device, allowing independent measurement of electrical variables. This segmentation eliminates mutual interference and magnetic saturation effects that would occur in a single integrated circuit, thereby improving measurement precision for short circuit detection.
Solution Approach 2:
The second star circuit acts as an intermediary reference system for measuring the electrical variables in the first star circuit. By measuring voltage and current in the second star circuit and comparing it with the first star circuit, the system can detect short circuits more accurately while filtering out common-mode interference from magnetic saturation and external components.
2Measurement precision
If complex analysis and filtering of measured electrical variable are applied, then measurement accuracy may improve, but the latency increases and construction becomes more complex
Solution Approach 1:
The measuring devices in both star circuits continuously monitor electrical variables (voltage and current) in real-time during normal operation. This preliminary continuous measurement allows the system to detect short circuits immediately when they occur, without requiring complex post-processing analysis or filtering that would introduce latency. The comparison between the two star circuits provides immediate detection capability.
3Measurement precision
If conventional single star circuit measurement is used, then the construction is simpler, but the signal-to-noise ratio is low making short circuit detection difficult
Solution Approach 1:
The measurement system is divided into two separate star circuits, each with its own measuring device. This segmentation creates two independent measurement channels that can be compared to enhance the signal-to-noise ratio. The first star circuit measures the actual electrical variables, while the second star circuit provides a reference measurement, allowing differentiation between actual short circuit signals and background noise from magnetic saturation.
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 enables precise detection of short circuits, reducing consequential damage by allowing quicker initiation of countermeasures and simplifying the construction, while maintaining high measurement accuracy and efficiency across various operating conditions.
Implementation Method 1
a measuring device that is electrically connected between the first star circuit and the second star circuit, for measuring an electrical variable
Implementation Method 2
the inverter unit is configured to modulate a temporally varying signal onto the AC voltage as a carrier signal
Implementation Method 3
Applying the three-phase AC voltage to the strands, and thus to the tooth windings, causes magnetic fields to build up. The magnetic fields move the rotor relative to the stator.
Data Source
AI summary
An electrical system (1A-1C) for an electric machine (2) comprises: at least three connections (A1-A3) for electrical connection to in each case one phase of an at least three-phase AC voltage; a first star circuit (10A-10C) with three strands (100A-100C) via each of which one of the at least three connections (A1-A3) is electrically connected to a common star point (101) of the first star circuit (10A-10C) and which each have at least (11A-11C) with three strands (110A-110C) via each of which one of the at least three connections (A1-A3) is electrically connected to a common star point (111) of the second star circuit (11A-11C) and which each have at least two tooth windings (Z) which are connected in series; and a measuring device (12), which is electrically connected between the first star circuit (10A-10C) and the second star circuit (11A-11C), for measuring an electrical variable.