Motor Coil Temperature Estimation Without Current Sensor
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Solution Overview
Problem
Conventional temperature estimation devices for motors require a current sensor to detect motor current, which is a limitation.
Innovation Solution
A temperature estimation device that estimates the coil temperature of a motor by processing circuitry, considering the influence of ambient temperature on energization, drive duty ratio, power consumption, and temperature variation, without using a current sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensor is used to detect motor current for temperature estimation, then temperature estimation accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the current sensor from the temperature estimation system. Instead of using a current sensor to detect motor current, the invention uses only voltage detection circuitry to acquire terminal voltage, and processes this voltage information through multiple calculation steps (including duty ratio estimation, power consumption estimation, and thermal model processing) to derive coil temperature without requiring current measurement hardware.
Solution Approach 2:
The patent introduces an intermediary processing mechanism that transforms voltage measurements into temperature estimates through intermediate calculations. The system uses the terminal voltage to estimate duty ratio, then uses the duty ratio to estimate power consumption, and finally combines power consumption with thermal models to estimate temperature. This intermediary processing chain replaces the direct current measurement approach.
2Reliability
If a current sensor is installed for temperature monitoring, then coil temperature control reliability is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent removes the current sensor component from the manufacturing requirements. By formulating a temperature estimation method that relies solely on voltage measurements and computational processing, the invention eliminates the need to source, install, and calibrate current sensors, thereby reducing manufacturing complexity and cost while maintaining temperature control reliability through sophisticated algorithmic processing.
3Measurement precision
If voltage and current are both measured for temperature estimation, then temperature estimation accuracy is improved, but the number of required sensors and system complexity increase
Solution Approach 1:
The patent extracts and removes the current sensor from the sensing system, achieving temperature estimation using only voltage measurements. The method processes the terminal voltage through duty ratio estimation and power consumption calculation to derive temperature information, eliminating the need for current sensing hardware while maintaining estimation capability.
Solution Approach 2:
The patent makes the voltage detection circuitry perform multiple functions: it not only monitors the terminal voltage for basic electrical characterization but also serves as the primary input for duty ratio estimation, power consumption calculation, and ultimately temperature estimation. This multi-functional use of a single sensing element replaces what would traditionally require separate voltage and current sensors.
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
Enables accurate estimation of coil temperature without a current sensor, improving motor control accuracy and eliminating the need for current sensor-based systems.
Implementation Method 1
When a voltage is applied to a direct-current motor, heat is generated by the resistance of a coil thereof and it raises the temperature of the coil
Data Source
AI summary
A temperature estimation device estimates a drive duty ratio by taking account of the influence of ambient temperature on the energization to a coil part, on the basis of a drive duty ratio and the ambient temperature, and estimates the power consumption of a motor when the coil part is energized with the estimated drive duty ratio, the power consumption of the motor, this power consumption being accompanied by the heat dissipation of the coil part, the power difference between both the power consumption values, the temperature time constant of the coil part, and a temperature variation during a period of the temperature time constant of the coil part, and estimates the temperature variation of the coil part from the ambient temperature on the basis of these estimated values and a last temperature variation of the coil part.