Brushless DC Motor Drive Reducing Start Noise via Non-Energizing Period
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Solution Overview
Problem
Brushless DC motors with a small number of poles face challenges in starting quietly and smoothly due to difficult frequency matching, defective starts, and noise issues during forced commutation, particularly with the 180° energizing method.
Innovation Solution
A motor drive apparatus with a position signal generation portion and logic portion that includes a non-energizing period after forced commutation, allowing for smooth transition to usual commutation based on rotor position signals during inertial rotation, thereby reducing noise and defective starts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If forced commutation method is employed for starting brushless DC motor with small number of poles, then rotor can be started to rotate, but difficult matching of forced commutation frequency occurs
Solution Approach 1:
The patent employs dynamic switching between two different energizing methods (120° energizing for start-up and 180° energizing for normal operation) based on rotor speed conditions. This dynamic approach allows the system to adapt to different operating phases, avoiding the frequency matching problems of forced commutation while ensuring reliable start-up and smooth transition to normal operation.
2Reliability
If forced commutation method is employed for starting brushless DC motor with small number of poles, then rotor can be started to rotate, but defective start occurs because of rotation ripple during forced commutation period
Solution Approach 1:
The patent extracts and eliminates the harmful forced commutation phase from the start-up process. Instead of using forced commutation with its associated rotation ripple, the system directly employs 120° energizing method which avoids generating rotation ripple, thereby preventing defective starts while ensuring reliable motor initiation.
3Reliability
If forced commutation method is employed for starting brushless DC motor with small number of poles, then rotor can be started to rotate, but large noise is caused by rotation ripple during forced commutation period
Solution Approach 1:
The patent converts the potential harm of using 180° energizing method directly (which would cause noise) by instead using it in a controlled manner after smooth start-up. The 120° energizing method is used first to quietly start the motor, then switching to 180° energizing method after transition, thereby benefiting from the quiet start-up characteristic while eventually achieving the desired operation mode.
4Reliability
If 120° energizing method is employed for starting brushless DC motor with small number of poles, then rotor can be started to rotate, but large motor start noise is generated
Solution Approach 1:
The patent employs dynamic switching between two different energizing methods (120° energizing for start-up and 180° energizing for normal operation) based on rotor speed conditions. This dynamic approach allows the system to adapt to different operating phases, avoiding the frequency matching problems of forced commutation while ensuring reliable start-up and smooth transition to normal operation.
Data Source
AI summary
A motor drive apparatus comprises: a position signal generation portion that generates a position signal corresponding to a rotor position of a brushless DC motor; and a logic portion that when starting the brushless DC motor, disposes a non-energizing period immediately after starting forced commutation at a phase switchover timing corresponding to a predetermined forced commutation frequency and performs energizing control of the brushless DC motor such that usual commutation is started at a phase switchover timing corresponding to the position signal that is generated during an inertial rotation of the rotor.