Three-Phase Brushless Motor State Identification via Phase Decoupling
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Solution Overview
Problem
Existing methods for determining the state of three-phase brushless motors often produce inaccurate results due to external influences like noise, leading to issues such as slow startup and overheating, which can cause significant motor damage.
Innovation Solution
A method involving decoupling the motor from the power source and using comparators to determine the voltage states of the phases relative to a common voltage, with repeated determinations if initial results are abnormal, and determining rotation direction based on phase voltage polarities and timing relative to a rising or falling third phase voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional techniques are used to determine motor state, then the determination process is simple, but the accuracy is low due to noise and external influences
Solution Approach 1:
The system performs preliminary actions by decoupling the motor from the power source before taking measurements. This preparatory step eliminates external electrical interference and ensures that subsequent voltage measurements reflect only the motor's back-EMF characteristics, thereby improving measurement accuracy without adding complex measurement equipment
Solution Approach 2:
The system implements feedback through repeated determination cycles. When the initial state determination shows identical voltage states across phases (indicating potential noise interference), the system automatically repeats the measurement process. This feedback mechanism filters out noise by requiring consistent results across multiple trials, significantly improving identification accuracy while maintaining a relatively simple procedural framework
2Reliability
If accurate motor state identification is implemented, then motor damage is prevented, but the determination process becomes more complex
Solution Approach 1:
The system decouples the motor from the power source before measurement, creating a controlled environment that eliminates power supply noise and external electrical interference. This preliminary isolation ensures that subsequent voltage measurements accurately reflect the motor's true state, improving reliability without requiring complex shielding or filtering hardware
Solution Approach 2:
The system uses feedback through repeated determination cycles to filter out noise and external influences. When measurements show identical voltage states across phases (a sign of noise interference), the system automatically repeats the measurement process until consistent results are obtained. This feedback mechanism significantly improves motor operation reliability by ensuring accurate state identification while adding minimal system complexity
3Measurement precision
If repeated determination is performed when voltage states are identical, then noise is filtered out, but the determination time increases
Solution Approach 1:
The system implements conditional feedback by repeating determinations only when voltage states are identical across phases, which indicates potential noise interference. This selective repetition approach filters out noise effectively while avoiding unnecessary time consumption in cases where the motor state is clearly identifiable, thus achieving a balance between measurement precision and time efficiency
Solution Approach 2:
The system applies partial action by performing repeated measurements only when necessary (i.e., when voltage states are identical and noise interference is suspected). Rather than continuously repeating measurements in all cases, the system selectively applies the repetition strategy only when the initial measurement shows ambiguous results, thereby maintaining high accuracy while minimizing time loss
Data Source
AI summary
A method for determining the state of a brushless motor having first, second and third phases, in some embodiments, comprises: decoupling said motor from a power source; determining whether said motor is rotating or non-rotating; if the motor is rotating, determining a first phase voltage state relative to a common voltage and a second phase voltage state relative to the common voltage, said first phase and second phase voltage states determined when a third phase voltage is within a predetermined range of said common voltage; and if the first phase voltage state and the second phase voltage state are the same, repeating said determination as to whether the motor is rotating or non-rotating.