Motor Controller Thermal Management via Duty Ratio Adjustment
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Solution Overview
Problem
Existing motor drive circuits fail to effectively detect and control the temperature of elements like choke coils and stator coils, leading to overheating issues, as they primarily focus on switching elements like FETs, resulting in unstable motor operation at high output.
Innovation Solution
A motor controller that includes a voltage generator, temperature detector, rotation speed detector, and voltage controller to compute and manage the temperature of various circuit elements by adjusting the duty ratio of the voltage based on detected temperatures, rotation speed, and load, with optional current detection and correction values for precise temperature computation and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature threshold value is set low to reliably protect switching elements, then the reliability of protection is improved, but the motor cannot stably rotate at high output
Solution Approach 1:
The patent segments the temperature monitoring function by introducing separate temperature detectors for different circuit locations (circuit board temperature detector and switching element temperature detector), allowing independent monitoring and control strategies for each component, thus resolving the conflict between protection reliability and motor output capability
Solution Approach 2:
The patent implements feedback control by continuously monitoring temperatures from multiple detectors and adjusting the duty ratio based on real-time temperature data, enabling dynamic balance between protection and performance rather than using a fixed low threshold
2Ease of manufacture
If the thermistor is mounted at a location away from switching elements, then the ease of manufacture is improved, but the temperature detection accuracy of switching elements deteriorates
Solution Approach 1:
The patent divides the temperature detection function into multiple independent detectors placed at different locations, allowing each detector to independently monitor its local temperature without requiring precise placement relative to other components, thus maintaining manufacturing ease while improving overall detection accuracy
Solution Approach 2:
The patent introduces a microcomputer as an intermediary that receives temperature data from multiple detectors and computes the switching element temperature based on combined information, enabling accurate temperature monitoring even when detectors are mounted at convenient locations rather than directly on switching elements
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
The motor controller effectively detects and suppresses overheating risks in all circuit elements, ensuring stable operation by adjusting the voltage duty ratio according to the computed temperatures, thereby maintaining reliable motor performance at high output.
Implementation Method 1
a thermistor, with a resistance value that varies according to temperature variation of a circuit board, is mounted on the circuit board to which the inverter circuit is mounted, and the temperature of the circuit board is detected from variations in the resistance value of the thermistor
Implementation Method 2
a voltage controller that controls the voltage generator so as to generate a voltage of a duty ratio based on a speed instruction value corresponding to operation of a switch for switching the rotation speed of the motor
Implementation Method 3
in cases in which a temperature of an element configuring the circuit, computed based on the temperature of the circuit detected by the temperature detector, the rotation speed of the motor detected by the rotation speed detector, and a load of the circuit, reaches a specific threshold value or above, controls the voltage generator so as to generate a voltage of a duty ratio that is lower than the duty ratio based on the speed instruction value
Data Source
AI summary
There is provided a motor controller including: a voltage generator that generates a voltage applied to a motor; a temperature detector that detects a temperature of a circuit; a rotation speed detector that detects a rotation speed of the motor; and a voltage controller that controls the voltage generator so as to generate a voltage of a duty ratio based on a speed instruction value, and that, in cases in which a temperature of an element configuring the circuit, computed based on the temperature of the circuit detected by the temperature detector, the rotation speed of the motor detected by the rotation speed detector, and a load of the circuit, reaches a predetermined threshold value or above, controls the voltage generator so as to generate a voltage of a duty ratio that is lower than the duty ratio based on the speed instruction value.