Electric Machine Loss Torque Measurement via Axial Torque Jump
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Solution Overview
Problem
Existing methods for determining the loss torque of an electric machine require measuring electrical parameters, which can be inaccurate and complex, involving torque flanges and strain gauges.
Innovation Solution
A method and system using piezoelectric elements to measure axial torque on a freely rotating rotor, where the electric machine is operated to reach a predefined speed, then abruptly switched to idle, identifying a jump in the torque signal to determine the loss torque without measuring electrical parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrical parameters are measured to determine loss torque, then measurement can be performed, but measurement accuracy is poor and device complexity increases
Solution Approach 1:
The patent replaces electrical parameter measurement with mechanical torque measurement using a torque sensor. Instead of measuring electrical quantities (current, voltage, power) and calculating loss torque through complex electrical models, the invention directly measures the mechanical torque at the shaft using a torque sensor, substituting an electrical measurement system with a mechanical one that provides more accurate and direct results.
Solution Approach 2:
The patent extracts the loss torque measurement from the complex electrical parameter measurement process. By using a torque sensor to directly measure the torque at the shaft, the invention separates the loss torque determination from the electrical parameter measurements, eliminating the need for complex electrical models and calculations while improving measurement accuracy.
2Measurement precision
If torque flanges and strain gauges are used to measure torque, then torque measurement is possible, but the rotor's moment of inertia is distorted
Solution Approach 1:
The patent introduces a torque sensor as an intermediary device that measures torque without being rigidly coupled to the rotor. The torque sensor is mounted on the shaft but allows the rotor to rotate freely, acting as a mediator that transfers torque information for measurement while not affecting the rotor's dynamic characteristics or moment of inertia.
Solution Approach 2:
The patent segments the measurement system from the rotor structure. Instead of integrating torque measurement components (torque flanges, strain gauges) into the rotor itself, the invention uses a separate torque sensor mounted on the shaft, dividing the system into independent measurement and rotation components that do not interfere with each other.
3Measurement precision
If load machines and speed ramps are used for measurement, then torque measurement can be performed, but the measurement process becomes more complex and time-consuming
Solution Approach 1:
The patent enables the system to measure loss torque during normal operation without requiring external load machines or complex test procedures. The torque sensor continuously monitors the torque at the shaft, and the control unit calculates loss torque in real-time based on the measured torque and rotor speed, allowing the system to self-diagnose and measure performance under actual operating conditions.
Solution Approach 2:
The patent implements continuous periodic measurement of torque and speed parameters during normal operation. Instead of requiring periodic shutdowns for complex measurement procedures with load machines, the system continuously monitors torque and speed, calculating loss torque in real-time through periodic data sampling and processing.
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 allows for accurate and simplified determination of loss torque without distorting the rotor's moment of inertia, eliminating the need for load machines and speed ramps, and providing precise measurement through piezoelectric elements.
Implementation Method 1
the measuring device has at least two, in particular at least three or four, piezoelectric elements, each with a preferred direction, which are arranged at different positions around an axis of rotation of the shaft
Data Source
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AI summary
The invention relates to a method for determining a loss torque of an electrical machine comprising a rotor, wherein the electrical machine is mounted on a measuring device in such a way that an axial torque on the machine can be measured, and wherein the rotor is freely rotatable, the method comprising the following working steps: operating the machine for a first time in such a way that the rotor reaches a predefined rotational speed; operating the machine for a second time to let it idle when the predefined rotational speed has been reached, wherein a signal from the measuring device, which signal represents the axial torque on the machine, is monitored; identifying a jump in the signal; and determining the value of the jump, wherein the value indicates the loss torque of the electrical machine.