Induction Motor Torque Estimation Without Torque Sensors
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Solution Overview
Problem
Existing methods for estimating induction motor torque are either costly due to the need for torque sensors or require additional hardware and sensors, making them impractical for widespread industrial use.
Innovation Solution
A method that calculates the induction motor torque using the ratio of output power to motor rotational speed, based on motor name plate information and measured operational parameters, without the need for sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque sensors are used to measure torque directly, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical torque sensor system with an electrical measurement system. Instead of using mechanical sensors to directly measure torque, the method calculates torque indirectly by measuring electrical parameters (input power, current, voltage) and computing torque from these measurements combined with motor characteristics, thereby eliminating the need for complex mechanical sensing equipment
Solution Approach 2:
The patent introduces electrical parameters as intermediary variables to bridge the gap between measurable quantities and the desired torque value. By measuring input power, current, and voltage, and using these as intermediaries in the calculation process, the system derives torque without requiring direct mechanical measurement, thus simplifying the overall system
2Measurement precision
If additional hardware and sensors are used for indirect torque estimation, then torque estimation is achieved, but device complexity and cost increase
Solution Approach 1:
The patent makes the motor's existing electrical measurement system perform multiple functions. The same electrical sensors and measurements used for basic motor control and monitoring are also utilized for torque estimation, eliminating the need for separate dedicated hardware and achieving torque estimation through multi-functional use of existing components
Solution Approach 2:
The motor system estimates its own torque using its own operational electrical parameters. By utilizing the motor's inherent electrical characteristics and measured parameters (input power, current, voltage), the system performs self-diagnosis and self-measurement without requiring external sensing equipment, thereby reducing hardware complexity
3Measurement precision
If torque sensors are used, then torque measurement accuracy is improved, but ease of operation and maintenance worsen
Solution Approach 1:
The patent replaces the mechanical torque sensor system with an electrical measurement system. Instead of using mechanical sensors to directly measure torque, the method calculates torque indirectly by measuring electrical parameters (input power, current, voltage) and computing torque from these measurements combined with motor characteristics, thereby eliminating the need for complex mechanical sensing equipment
Data Source
AI summary
Some embodiments relate to a method of estimating induction motor torque. The method can include calculation of the ratio of output power (P01) to motor rotational speed (N1). The calculation includes determining, using motor name plate information (NPI), rated motor information; measuring motor operational parameters, the parameters including rotational speed (N1), root mean squared, RMS, current (I1), input power (Pi1) and supply frequency (f1); calculating rated motor power losses; calculating total motor operational power losses (Ploss1) from a combination of individual motor operational power losses; determining output power (Po1) from the measured input power (Pi1) and the total motor operational power loss (Ploss1). The induction motor torque (T1) is calculated using the ratio of output power (P01) to motor rotational speed (N1).