Sensorless Switched Reluctance Motor Startup via Inductance Oscillation
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Solution Overview
Problem
Switched reluctance motors require a lengthy alignment phase without a position sensor, leading to user dissatisfaction and potential misinterpretation of device failure due to the dead time before operation, especially in applications like vacuum cleaners.
Innovation Solution
A method and control unit that aligns the rotor by energizing phases, detecting inductance values to determine alignment, and initiating oscillation to identify the correct direction of rotation for starting, eliminating the need for a position sensor and reducing startup time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a position sensor is used to determine rotor position, then the alignment phase can be minimized, but the device complexity increases and reliability decreases due to sensor contamination risks
Solution Approach 1:
The patent extracts and eliminates the position sensor from the system entirely. Instead of using a sensor to detect rotor position, the invention uses sensorless detection methods by evaluating current characteristics and inductance values during the alignment phase, thereby removing the reliability issues associated with sensor contamination while still achieving quick alignment.
Solution Approach 2:
The patent replaces the mechanical/optical position sensor system with an electrical field-based detection method. By measuring inductance values and current characteristics in the motor windings, the system determines rotor position without physical contact or optical components that are susceptible to contamination.
2Speed
If a position sensor is used to determine rotor position, then alignment speed increases, but the device complexity increases
Solution Approach 1:
The patent removes the position sensor component entirely, reducing device complexity. The alignment function is achieved through software-based evaluation of existing electrical parameters (current, inductance) rather than adding hardware sensors, thereby simplifying the overall device structure while maintaining fast alignment capability.
Solution Approach 2:
The motor system uses its own electrical characteristics (current consumption, inductance values) to determine rotor position and achieve alignment. This self-service approach eliminates the need for external position sensing hardware, reducing complexity while maintaining alignment speed.
3Reliability
If the rotor is aligned before startup in sensorless mode, then the alignment phase takes a long time, but the reliability increases by avoiding position sensors
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors current characteristics and inductance values during the alignment phase. By evaluating these parameters in real-time, the system can detect when the rotor has reached the aligned position and terminate the alignment phase early, significantly reducing the alignment time while maintaining reliability through sensorless operation.
Solution Approach 2:
Instead of waiting for complete mechanical settling of the rotor (excessive action), the patent uses partial action by detecting alignment through electrical parameter evaluation before the rotor fully settles. This allows the system to proceed with startup earlier, reducing alignment time while ensuring sufficient alignment through electrical field detection.
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 quick and reliable startup of the reluctance motor, improving user experience by eliminating the long alignment phase and reducing the risk of user-perceived device failure.
Implementation Method 1
The teeth with the energized windings each attract the nearest teeth of the rotor like an electromagnet
Implementation Method 2
detecting the inductance values of the at least two phases
Implementation Method 3
Energizing only the phase with the detected smaller inductance value in order to generate an oscillation of the rotor around this phase
Data Source
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AI summary
The invention relates to a method for controlling a reluctance motor (110) with a rotor (145) having a preferred direction in the aligned state and a stator with at least two phases (phase 1, phase 2, 135a, 135b), wherein the method comprises the following steps: energizing at least one first phase (phase 1, 135a) and a second phase (135b) to excite the rotor (145) to oscillate about the first (phase 1, 135a) or the second phase (135b); detecting the inductance values of the at least two phases (phase 1, phase 2, 135a, 135b) to determine the phase with the higher inductance value; energizing only the phase with the detected lower inductance value to excite an oscillation of the rotor (145) about this phase, and detecting a first profile of the inductance value of the other phase;and starting the reluctance motor (110) when, in the first phase of the inductance value, a local maximum is followed by another local maximum with a larger amplitude.