Rotating Electric Machine Performance from Stray Magnetic Field
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Solution Overview
Problem
Existing methods for determining the operational performance of rotating electric machines, such as asynchronous machines, are inaccurate due to reliance on linear interpolation or extrapolation from synchronous and slip frequencies, resulting in errors between 5% and 10% or higher, especially when external sensors are not used.
Innovation Solution
A sensor apparatus detects the leakage magnetic field to calculate slip and synchronous frequencies, which are then used with an enhanced equivalent circuit diagram and machine-specific parameters to determine operational performance, including torque, power, and efficiency, without the need for costly external sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If linear interpolation or extrapolation from synchronous and slip frequencies is used to determine operational performance, then the method is simple and cost-effective, but the measurement precision deteriorates with errors between 5% and 10% or higher
Solution Approach 1:
The patent replaces the mechanical/mathematical linear interpolation method with a magnetic field-based detection system. A sensor detects the leakage magnetic field generated by the machine, and signal processing extracts synchronous and slip frequencies directly from this magnetic field information, substituting the inaccurate linear calculation approach with a physics-based measurement approach that captures the actual magnetic field characteristics of the machine.
Solution Approach 2:
The patent introduces the leakage magnetic field as an intermediary carrier that conveys information about the machine's operational state. The magnetic field serves as a mediator between the machine's internal operations (rotor speed, torque) and the external measurement system, allowing indirect but accurate measurement of operational parameters without direct contact with moving parts or complex sensor installations.
2Measurement precision
If external sensors are used to directly measure operational variables, then the measurement precision improves, but the device complexity and cost increase
Solution Approach 1:
The patent extracts the essential measurement information (synchronous and slip frequencies) from the leakage magnetic field that is already present outside the machine. Instead of installing sensors inside the machine or using complex multi-sensor arrays, the system extracts the needed frequency information from the naturally occurring magnetic field, simplifying the measurement apparatus while maintaining accuracy.
Solution Approach 2:
The sensor apparatus is designed to detect the leakage magnetic field which contains multiple pieces of information (synchronous frequency, slip frequency, and their relationship) that can be used to determine various operational parameters. This single magnetic field detection approach serves multiple measurement functions simultaneously, reducing overall system complexity compared to using separate sensors for each parameter.
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 approach significantly improves the accuracy of determining operational performance by directly calculating slip and synchronous frequencies from the leakage magnetic field, using an enhanced equivalent circuit diagram with machine-specific parameters, reducing errors and eliminating the need for costly sensors.
Implementation Method 1
the sensor apparatus is designed to detect a leakage magnetic field outside the machine
Data Source
AI summary
The invention relates to an arrangement for determining the operational performance of a rotating electric machine (2) connected to an operating voltage, wherein: the arrangement (3) comprises a sensor apparatus (4) and a computing device (5, 6, 8, 9); the sensor apparatus (4) is designed to capture a stray magnetic field outside the machine (2) and to calculate from the captured stray magnetic field a slip frequency (f2) and a synchronous frequency (f1); an enhanced equivalent circuit diagram comprising predetermined, machine-specific parameters (R1, X1 Rfe, Xh, R′2, X′2, Rzus) is stored on the computing device (5, 6, 8, 9) and the computing device (5, 6, 8, 9) is configured to determine, on the basis of the calculated slip frequency (f2) and synchronous frequency (f1), a slip (s) and then to determine the operational performance of the machine (2) by means of the enhanced equivalent circuit diagram.