Sensorless Motor Drive PWM Control for Immediate Restart
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Solution Overview
Problem
Motor drive systems with sensorless control face challenges in immediate restart functionality during stop operations, requiring additional algorithms to manage PWM signal duty ratios effectively.
Innovation Solution
A motor drive apparatus with an inverter and control unit that decreases the PWM signal duty ratio during a stop command, allowing for immediate restart by increasing the duty ratio when a restart command is input, maintaining sensorless control throughout the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sensorless control is used to reduce production costs, then manufacturing cost is reduced, but immediate restart capability during stop operation deteriorates
Solution Approach 1:
The control unit maintains sensorless control algorithms active during stop operations, performing preliminary estimation of rotor position and speed even when the motor is stationary. This preliminary action ensures that when a restart command is received, the control unit already has the necessary rotor information to immediately restart the motor without requiring additional algorithms or sensors.
2Speed
If PWM duty ratio is decreased during stop command, then motor speed is reduced to stop, but response time for restart increases
Solution Approach 1:
The control unit continues to execute sensorless control algorithms continuously during stop operations, maintaining the estimation of rotor position and speed throughout the stop period. This continuous action ensures that when a restart command is received, the control unit immediately has updated rotor information available, enabling immediate restart without waiting for additional measurements or algorithms to initialize.
3Productivity
If additional algorithms are implemented for quick restart, then restart speed is improved, but device complexity increases
Solution Approach 1:
The control unit is designed to perform multiple functions using the same sensorless control algorithms: it estimates rotor position and speed during both operation and stop periods, and uses this information for both normal control and immediate restart. This multi-functionality eliminates the need for separate additional algorithms specifically for restart, as the existing sensorless control framework handles both scenarios.
Data Source
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AI summary
The present invention relates to a motor drive apparatus and, more particularly, to a motor drive apparatus capable of immediately restarting by maintaining sensorless control during a stop operation of a motor. The motor drive apparatus comprises: an inverter for driving a motor by using an AC voltage; and a control unit for controlling operations of a switching element included in the inverter. At this time, when a stop command is input, the control unit decreases a duty ratio of a PWM signal until a present speed of the motor becomes smaller than a predetermined minimum speed, thereby decreasing the revolutions per minute of the motor. Then, when a restart command is input in a state where the duty ratio of the PWM signal is decreased, the control unit can immediately restart the motor by increasing the duty ratio of the PWM signal.