Sensorless BLDC Motor Startup Using Phase Current Eye Detection
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Solution Overview
Problem
Existing BLDC motors require prior knowledge of rotor position and use position sensors for stable and quiet operation, which limits their applicability and increases complexity and cost, especially in scenarios with unknown or changing rotor states.
Innovation Solution
A method for starting and operating a BLDC motor without prior knowledge of the rotor position, using a control and evaluation unit to execute a sequence of steps including initialization, partial cycles, and overall cycles, where commutation is based on detecting current eyes between phase currents, allowing for immediate or timed commutation without sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If position sensors are used for sensor-controlled commutation, then stable and quiet operation is achieved, but device complexity and cost increase
Solution Approach 1:
The system uses its own phase currents to detect rotor position information through current eye detection, eliminating the need for external position sensors. The motor system serves its own positioning needs by analyzing its operational characteristics
Solution Approach 2:
Physical position sensors are replaced with an electronic detection method that analyzes current characteristics. The mechanical/sensor-based position detection is substituted with an electrical measurement approach using phase current analysis
2Reliability
If position sensors are used for sensor-controlled commutation, then stable and quiet operation is achieved, but cost increases
Solution Approach 1:
The invention replaces expensive position sensors with a low-cost electronic control approach that uses existing phase current measurements. The solution uses inexpensive computational methods rather than costly hardware components
Solution Approach 2:
The system uses its own operational data (phase currents) to determine rotor position, eliminating the need for additional expensive sensing components. The motor's own electrical characteristics are exploited for position detection
3Device complexity
If sensorless commutation methods are used, then device complexity is reduced, but reliable operation with unknown rotor position becomes difficult
Solution Approach 1:
The system performs preliminary rotor positioning during startup by applying voltage and detecting current eyes to establish initial rotor position and orientation before normal operation begins. This preliminary action ensures reliable operation from standstill
Solution Approach 2:
The system continuously monitors phase currents and detects current eyes to determine rotor position in real-time, providing feedback for commutation control. This closed-loop approach ensures reliable operation without position sensors
4Ease of manufacture
If traditional sensorless methods are used, then cost is reduced, but startup time and reliability with unknown rotor states increase
Solution Approach 1:
The system performs preliminary rotor positioning during startup by applying voltage and detecting current eyes to establish initial rotor position and orientation before normal operation begins. This preliminary action ensures reliable operation from standstill
Solution Approach 2:
Physical position sensors are replaced with an electronic detection method that analyzes current characteristics. The mechanical/sensor-based position detection is substituted with an electrical measurement approach using phase current analysis
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 stable and quiet operation of BLDC motors without position sensors, suitable for various applications including fan motors on vehicle coolers, and is robust against load and voltage fluctuations, reducing startup time and complexity.
Implementation Method 1
To generate a rotating magnetic field, the stator coils are controlled by an electronic circuit at different times. Due to the rotating field generated, a torque of the permanently excited rotor can thus be brought about.
Implementation Method 2
a movable rotor, which is usually formed from permanent magnets. To generate a rotating magnetic field, the stator coils are controlled by an electronic circuit at different times. Due to the rotating field generated, a torque of the permanently excited rotor can thus be brought about.
Data Source
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AI summary
The invention relates to a method for starting and operating a BLDC motor, wherein the BLDC motor has a rotor (1), a stator (2) and a control and evaluation unit (3), wherein the rotor (1) has exciter magnets, and the stator (2) has at least three stator coils, wherein in each case one phase current can be applied to each of the at least three stator coils, and wherein a rotating stator magnetic field can be generated by means of the stator coils, having the following method steps: a) carrying out an initialisation phase, b) carrying out a partial cycle, including b1) carrying out a rising phase, wherein a current field angle is increased until a final field angle is reached which exceeds a starting field angle of 60, b2) carrying out an analysis phase, wherein the current field angle remains constant on account of the application of voltage to the stator coils remaining constant, wherein continuous detection of a difference in current between two phase currents in the same direction of flow is carried out, c) repeatedly carrying out the partial cycle, wherein the partial cycle is repeated until the final field angle has risen to a value of 360°, wherein the partial cycles together form a total cycle, d) repeatedly carrying out the total cycle. The invention also relates to a BLDC motor with which the method can be carried out.