Motor Control System Abnormal Rotation Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Motor control systems face challenges in reducing system costs while effectively detecting abnormal rotation states and calculating rotation numbers of motors, especially in one-shunt resistor type brushless/sensorless three-phase motors, which require precise current detection without increasing the number of parts.
Innovation Solution
A motor control system incorporating a microcontroller, inverter, current detection circuit, and shunt resistor, where at least one low-side transistor is turned on to detect a combined detection current through a shunt resistor, allowing judgment of abnormal rotation and calculation of rotation number based on the current waveform, reducing the need for multiple shunt resistors and parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a one-shunt resistor type motor is used to reduce system cost, then the number of parts is reduced and system cost is cut down, but the ability to detect abnormal rotation before starting is compromised
Solution Approach 1:
The system performs preliminary detection of abnormal rotation before the motor starts by turning on all low-side transistors simultaneously and detecting the combined current. This preliminary action allows the system to identify issues before normal operation begins, ensuring reliability without requiring three separate shunt resistors.
Solution Approach 2:
The single shunt resistor serves multiple functions: it detects combined current for abnormal rotation detection before starting, and continues to function for current measurement during normal operation. This multi-functionality eliminates the need for separate detection components while maintaining reliability.
2Reliability
If three-shunt resistor type motor is used to enable individual current detection, then abnormal rotation detection capability is improved, but the number of parts increases and system cost rises
Solution Approach 1:
The patent merges the detection function of three separate shunt resistors into a single shunt resistor by combining the current paths. When all low-side transistors are turned on simultaneously, the combined current flows through the single shunt resistor, allowing abnormal rotation detection without requiring three separate components.
Solution Approach 2:
The single shunt resistor is designed to handle multiple detection scenarios: it measures individual phase currents during normal operation and measures the combined current of all phases during preliminary abnormal rotation detection, making it a universal detection component that replaces multiple specialized components.
3Device complexity
If combined current detection through shunt resistor is implemented, then system cost is reduced and complexity is lowered, but measurement precision for individual phase currents is lost
Solution Approach 1:
The detection process is segmented into two distinct modes: individual phase current detection during normal operation (when only one low-side transistor is on at a time) and combined current detection during abnormal rotation screening (when all low-side transistors are on simultaneously). This segmentation allows the system to use the single shunt resistor for both purposes without compromising individual phase measurement accuracy during normal operation.
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 enables precise detection of motor states and abnormal rotations with reduced system complexity and cost, allowing for effective motor control and abnormal rotation identification.
Implementation Method 1
In a shunt resistor, one end is connected to a plurality of low potential side terminals of the low side transistors, and the other end is connected to a ground potential. The current detection circuit detects currents flowing through the shunt resistor.
Data Source
AI summary
According to an embodiment, a motor control system includes an inverter, a PWM generation circuit, a shunt resistor, and a current detection circuit. Before the starting of the motor, at least one of all the low side transistors is turned on for a first period and detection of a first detection current flowing through the shunt resistor is performed. When the first detection current is detected, it is judged that the motor is rotating abnormally, and the rotation number of the motor is calculated based on the waveform of the first detection current. When the first detection current is not detected, it is judged that the motor is being stopped.