Instantaneous Angular Speed Identification via Stator Signals
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Solution Overview
Problem
Existing methods for monitoring the condition of electromechanical systems, such as Motor Current Signature Analysis (MCSA), struggle with accurately determining instantaneous angular speed in non-stationary operating conditions, particularly in applications like grinding and pulping, where traditional sensors like tachometers or encoders are costly, difficult to install, and unreliable.
Innovation Solution
A method that estimates discrete instantaneous angular speed using a simplified mathematical model based on stator currents and voltages, dependent on a single parameter - the average rotor time constant, allowing for robustness against parameter variations and eliminating the need for detailed machine knowledge or training periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensors like tachometers or encoders are used to measure shaft speed, then accurate angular speed measurement can be achieved, but the system becomes more costly, difficult to install, and less reliable
Solution Approach 1:
The patent replaces mechanical sensors (tachometers or encoders mounted on the shaft) with an electrical measurement system that uses stator currents and voltages to estimate rotor speed. This substitution eliminates the need for physical contact with the rotating shaft, reducing installation complexity and improving reliability while maintaining measurement accuracy through electrical signal analysis
Solution Approach 2:
The patent introduces an intermediate estimation process that uses easily measurable electrical quantities (stator currents and voltages) as mediators to infer the difficult-to-measure mechanical quantity (rotor speed). This intermediary approach avoids direct mechanical measurement while achieving the same information goal
2Device complexity
If Motor Current Signature Analysis is performed with traditional assumptions of constant operating speed, then analysis is simpler, but it fails to accurately capture instantaneous angular speed in non-stationary conditions
Solution Approach 1:
The patent transitions from static analysis assumptions (constant speed) to dynamic analysis that captures instantaneous angular speed variations. By using a mathematical model that incorporates time-varying electrical signals and computes derivative relationships, the system adapts to non-stationary operating conditions while maintaining computational tractability through efficient numerical methods
3Measurement precision
If advanced speed estimation methods using multiple parameters or training periods are used, then accuracy may improve, but the computational complexity increases and implementation becomes more difficult
Solution Approach 1:
The patent extracts and isolates the single most critical parameter (rotor time constant) from the complex set of motor parameters, eliminating the need for detailed machine knowledge or multiple parameter identification. This extraction simplifies the implementation while maintaining accuracy by focusing computational effort on the dominant time constant rather than attempting to precisely determine all motor parameters
Solution Approach 2:
The patent changes the approach from using multiple time-varying parameters to using a single average rotor time constant. This parameter simplification reduces computational complexity while maintaining estimation accuracy by averaging out the effects of parameter variations over the measurement period
Data Source
AI summary
A method for identifying the discrete instantaneous angular speed of electromechanical systems in which electrical rotating machinery is used and in which at least one electrical signal is measured during an operation of the electromechanical system. The method includes measuring analog stator current signals and analog stator voltage signals for at least one phase A, B, C, converting the measurements into a digital discrete form, transmitting the digital discrete signals to a computer device wherein data analysis is performed in a processor unit on the basis of a simplified mathematical model of the dynamics of the motor or generator. During the data analysis an average rotor time constant is calculated, an average supply frequency value is identified, an average angular speed is obtained, and an instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals is determined. The discrete instantaneous angular speed is identified by combining the average supply frequency value, the instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals, the average rotor time constant, and a number of pole pairs of the electric motor, given by the user. The result of combining the data is stored in a memory of the processor unit.