Virtual Motor Temperature Sensing From Power and Shaft Speed
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Solution Overview
Problem
Existing methods for determining the temperature of an electric motor without using a temperature sensor or measuring device inside the motor are inefficient and unreliable, necessitating a more effective monitoring system to prevent overheating.
Innovation Solution
A system utilizing a 'virtual' sensor based on a thermal model that simulates the motor's thermal behavior, incorporating electrical input power and shaft speed measurements, with a differential equation system to calculate the motor temperature, allowing for numerical or analog solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is installed in the motor winding to directly measure temperature, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent creates a virtual copy of the temperature sensor by using a thermal model that replicates the temperature measurement function through mathematical calculations based on electrical parameters, eliminating the need for physical sensor installation in the motor winding
Solution Approach 2:
The patent replaces the mechanical/physical temperature sensor system with an electrical calculation system that uses measured electrical parameters (current, voltage, frequency) and thermal models to determine temperature, substituting direct physical measurement with indirect electrical measurement
2Measurement precision
If thermal models with multiple parameters are used to improve temperature estimation accuracy, then measurement precision improves, but device complexity and computational requirements increase
Solution Approach 1:
The patent dynamically adjusts thermal model parameters based on operating conditions (frequency, current, voltage) to maintain accuracy across different motor operating states, using parameter adaptation rather than fixed complex models
Solution Approach 2:
The patent implements a dynamic thermal model that continuously adapts to changing operating conditions by updating parameters in real-time based on measured electrical quantities, rather than using static complex models
3Measurement precision
If high-frequency voltage signals are applied to determine winding resistance for temperature calculation, then measurement precision improves, but power loss and stress on the motor increase
Solution Approach 1:
The patent uses periodic measurement cycles where high-frequency signals are applied only at specific intervals rather than continuously, reducing overall power loss while maintaining measurement accuracy when needed
Solution Approach 2:
The patent applies high-frequency signals only partially (at selected measurement points) rather than continuously, providing sufficient measurement data without excessive energy input that would cause unnecessary power loss and motor stress
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 provides a reliable and efficient method for monitoring motor temperature, preventing overheating by accurately calculating the temperature increase using thermal power loss and a reference temperature, thus ensuring effective engine protection.
Implementation Method 1
a thermal model (MOD) which represents the thermal behavior of the motor
Implementation Method 2
calculating the motor temperature from the input power, a reference temperature TRef, the determined shaft speed n and the thermal model
Data Source
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AI summary
The present invention relates to a system (1) for monitoring the temperature of a motor (M) with an electromechanically driven motor shaft, comprising a sensor (10) based on a thermal model (MOD) describing the thermal behavior of the motor (M), a measuring means for determining the electrical input power (P) of the motor (M), and a measuring means for detecting the shaft speed n of the motor shaft, wherein an evaluation device is further provided which is configured to determine the current motor temperature of the motor (M) from the input power (P), a reference temperature TRef, the determined shaft speed n, and the thermal model (MOD).