BLDC Compressor Motor Control Using 90° Conduction at Low Speed
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Solution Overview
Problem
BLDC motors used in refrigerators face challenges in detecting rotor position at low speeds due to small pulse duty of driving current, making it difficult to control the motor efficiently, especially in high-temperature and high-pressure environments where sensors are unreliable.
Innovation Solution
A BLDC motor driving apparatus that increases the pulse duty of driving current during low-speed operation by switching between 120 degree and 90 degree conduction methods based on temperature sensing, using a control unit to adjust the driving mode and calculate rotor position through back electromotive force detection, thereby improving rotor position sensing and motor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pulse duty of driving current is decreased to achieve low-speed operation, then energy consumption is reduced, but rotor position detection becomes difficult
Solution Approach 1:
The patent applies dynamics by making the conduction angle variable rather than fixed. The control unit dynamically adjusts the conduction angle of the inverter circuit between 120 degrees and 90 degrees based on the operating speed requirements. This dynamic adjustment allows the system to optimize both energy consumption and rotor position detection accuracy at different operating conditions, resolving the contradiction between low energy consumption and accurate detection.
Solution Approach 2:
The patent changes the electrical parameter (conduction angle) of the driving circuit to resolve the contradiction. By switching the conduction angle between 120 degrees and 90 degrees, the system alters the current waveform characteristics and pulse duty ratio, enabling improved rotor position detection through back-EMF while maintaining energy-efficient low-speed operation. This parameter change directly addresses both the energy consumption and detection accuracy requirements.
2Measurement precision
If a sensor is used to detect rotor position, then detection accuracy is improved, but device complexity and reliability in high-temperature high-pressure environments worsen
Solution Approach 1:
The patent applies self-service by enabling the BLDC motor to detect its own rotor position using back electromotive force (back-EMF) generated during normal operation, without requiring external sensors. The control unit extracts position information from the voltage induced in the non-driven phase winding, allowing the motor to self-diagnose its state. This eliminates the need for additional sensors, reducing device complexity and improving reliability in harsh environments.
Solution Approach 2:
The patent replaces the mechanical sensor-based detection system with an electrical field-based detection method. Instead of using physical sensors that require installation in high-temperature and high-pressure environments, the system uses electromagnetic induction to detect rotor position through back-EMF measurement. This substitution eliminates the need for mechanical components in harsh environments, reducing complexity and improving reliability.
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 enhances the efficiency and accuracy of rotor position detection and motor control at low speeds, leading to improved power-saving operation and reduced energy consumption in refrigerators.
Implementation Method 1
the position sensing unit may detect back electromotive force generated from coils of the BLDC motor
Data Source
AI summary
A motor driving apparatus and a refrigerator using the same is provided. The refrigerator may include a compressor, a motor, a driving unit, temperature sensing units sensing the temperatures of storage chambers and an external temperature, and a control unit selecting a driving mode of the driving unit based on the sensing result of the temperature sensing units and controlling the driving unit to drive the motor according to the selected driving mode. In a general operation mode, the control unit controls the driving unit to drive the motor in a 120 degree conduction method, and in a power-saving operation mode, the control unit controls the driving unit to drive the motor in a 90 degree conduction method. The refrigerator increases a pulse width of driving current by converting the conduction method of the motor to drive the motor at a low speed during power-saving operation of the refrigerator.