Sensorless Single-Phase Synchronous Motor Control via Induced Voltage
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Solution Overview
Problem
Existing methods for operating single-phase synchronous motors require rotor position sensors, which increase costs and complexity, and are limited in robustness, especially during startup, as they cannot start in closed-loop operation and are sensitive to external influences.
Innovation Solution
A method that energizes the stator with a predetermined voltage sign until a current threshold is reached, detects the induced voltage at zero crossing, and adjusts the voltage sign based on the induced voltage's sign, allowing sensorless operation and controlled startup from standstill with continuous sampling of induced voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotor position sensor is used to determine rotor position for controlled operation, then control precision is improved, but device complexity and manufacturing costs increase
Solution Approach 1:
The patent extracts the rotor position detection function from a dedicated sensor and relocates it to the existing current sensor by utilizing the induced voltage signal present in the motor current during operation. This eliminates the need for separate rotor position sensors and their complex wiring while maintaining position detection capability.
Solution Approach 2:
The current sensor serves dual functions: monitoring motor current for protection purposes and detecting rotor position through induced voltage analysis. This multi-functionality eliminates the need for dedicated position sensors and reduces overall system complexity.
2Measurement precision
If a rotor position sensor is installed to enable controlled operation, then control precision is improved, but installation space requirements increase
Solution Approach 1:
The current sensor performs both current monitoring and position detection functions, eliminating the need for additional position sensors and their associated installation space. The induced voltage signal from the motor windings provides the necessary position information without requiring extra components.
3Ease of operation
If the motor is started in open-loop operation before switching to closed-loop, then startup is achieved, but robustness is reduced due to sensitivity to external influences
Solution Approach 1:
The patent implements feedback-based closed-loop control from startup by using the induced voltage signal to determine rotor position and commutation timing. This eliminates the need for open-loop startup and makes the motor insensitive to external influences throughout the entire operation including startup.
Solution Approach 2:
The system performs preliminary determination of rotor position and commutation timing using induced voltage analysis before actual motor rotation begins, enabling immediate closed-loop control from standstill without requiring open-loop pre-positioning.
4Device complexity
If sensorless operation is implemented to reduce costs and complexity, then manufacturing costs are reduced, but measurement precision of rotor position deteriorates
Solution Approach 1:
The patent replaces the mechanical/electrical sensor system with an electronic signal analysis approach, using the induced voltage waveform in the current to extract rotor position information. This substitution maintains precision while eliminating physical sensors and their wiring.
Solution Approach 2:
The induced voltage signal acts as an intermediary carrier that conveys rotor position information without requiring direct physical sensing. By analyzing this intermediate signal, the system achieves accurate position detection through existing current measurement infrastructure.
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
Enables robust and cost-effective operation of single-phase synchronous motors without sensors, allowing for controlled startup and continuous operation across varying loads, improving reliability and reducing manufacturing complexity.
Implementation Method 1
detecting an induced voltage of the stator
Data Source
Figure 1~2
AI summary
The invention relates to a method for operating a drive system (1-4) with a single-phase synchronous motor (1) comprising at least the following steps: • Energizing (300) a stator (10) of the single-phase synchronous motor (1) with a motor voltage (U_motor) with a predetermined sign until a predetermined current threshold (I_ref) of a motor current (I_motor) of the stator (10) is reached, • Terminating (400) the energizing (300), • Continuously sensing (500) the motor current (I_motor) of the stator (10), • In the region of the zero crossing of the motor current (I_motor), sensing (600) an induced voltage (Bemf_Sample) of the stator (10), • Determining (700) the sign of the induced voltage (Bemf_Sample), and • if the sign of the induced voltage (Bemf_Sample) opposite sign to the predetermined sign of the motor voltage (U_motor) is,Changing (800) the predetermined sign of the motor voltage (U_motor) to the sign of the induced voltage (Bemf_Sample).