Motor-Generator Control Apparatus Rectangular Wave Switching
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Solution Overview
Problem
Existing control methods for brushless motors require expensive magnetic pole position sensors and result in high switching losses, making them inefficient and costly for applications like light automobiles and motorcycles.
Innovation Solution
A control apparatus for a motor-generator using a simplified magnetic pole position sensor and a multi-phase inverter with switch elements driven by a rectangular wave pattern, reducing switching frequency and eliminating the need for precise magnetic pole detection, while using mass-produced general-purpose devices like MOSFETs and parasitic diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If sinusoidal PWM controlled inverter is used to obtain stable rotational speed, then rotational speed stability is improved, but magnetic pole position sensor is required which increases cost
Solution Approach 1:
The patent extracts and eliminates the magnetic pole position sensor from the system by using a simplified sensorless control method that determines rotor position through back-EMF detection and rectangular wave control, thereby reducing cost while maintaining control functionality
Solution Approach 2:
The patent replaces the expensive magnetic pole position sensor with a cost-effective rectangular wave control approach that uses basic voltage detection circuits, achieving acceptable rotational speed stability at lower cost
2Ease of operation
If all elements are subject to switching to achieve speed control, then speed control capability is improved, but switching losses increase which lowers system efficiency
Solution Approach 1:
The patent employs periodic rectangular wave switching patterns with specific duty cycles (α and β angles) to control motor phases, reducing the frequency and duration of switching events compared to continuous PWM switching, thereby lowering switching losses while maintaining speed control
Solution Approach 2:
The patent applies partial switching control where only necessary phases are switched at specific times during the rectangular wave cycle, rather than continuously switching all elements, optimizing the balance between control capability and switching loss reduction
3Measurement precision
If high switching frequency is used for precise control, then control precision is improved, but cooling requirements increase and noise protection becomes more complex
Solution Approach 1:
The patent uses periodic rectangular wave control with optimized switching intervals (α>0° and β<180° constraints) to achieve adequate control precision at lower switching frequencies, reducing thermal and electromagnetic interference that would require complex cooling and noise protection
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 achieves excellent rotating speed characteristics, reduces cooling and noise protection needs, and decreases switching losses by one-third, making the system more efficient and cost-effective for motor-generator applications.
Implementation Method 1
the switch element of a low side connected to the switch element of a high side in series is subject to PWM switching control while the switch element of the high side is in an off-state
Implementation Method 2
a stator which includes multi-phase coils connected so as to form a star shape; a rotor which is coaxial with the stator and is arranged in the radial direction via a predetermined gap
Implementation Method 3
using mass-produced general-purpose devices like MOSFETs and parasitic diodes
Data Source
AI summary
A control apparatus for a motor-generator includes a stator including multi-phase coils, a rotor, a multi-phase inverter one arm of which includes a switch element and a free-wheeling element, and a power supply connected between a neutral point of the coils and a negative electrode of the inverter. When the switch elements are driven by rectangular wave, the low-side switch element connected to the high-side switch element is subject to PWM switching control while the high-side switch element is off. When a time point, at which the high-side switch element is turned off, is defined as a base point, if α is defined as a time when switching of the low-side switch element starts, and β is defined as a time when the switching ends, β-α is 120 degrees in electrical degree or more, α is more than 0 degrees, and β is less than 180 degrees.