Rotary Electric Machine Control Using Constant Conduction Ratio
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Solution Overview
Problem
Conventional toothless-winding rotary electric machines face challenges with current detection and control due to low inductance and high current requirements, leading to distorted current waveforms and vibration noise, especially when using high-speed switching frequencies.
Innovation Solution
A control apparatus and method for a rotary electric machine with a toothless winding configuration, utilizing a drive circuit with switching elements and a control unit that maintains a conduction ratio of switching elements for each phase at a constant value between 120 degrees and 180 degrees electrical angle, and employing high-frequency conduction ratio constant control to stabilize rotation and reduce current pulsation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed switching frequency is used in toothless-winding rotary electric machines, then switching speed is improved, but current waveform distortion and vibration noise increase
Solution Approach 1:
The patent applies periodic action by maintaining a constant conduction ratio for a predetermined period (120-180 electrical degrees) in each phase. This periodic control pattern stabilizes the current waveform during each switching cycle, reducing distortion and vibration noise even at high switching frequencies. The control unit repeatedly applies this constant conduction ratio pattern across multiple switching cycles.
Solution Approach 2:
The patent changes the conduction ratio parameter to a constant value maintained over a predetermined period (120-180 electrical degrees). This parameter change from variable to constant conduction ratio during the effective period stabilizes the current waveform and reduces harmful effects while allowing high-speed switching operation.
2Measurement precision
If conventional current feedback control is used, then current detection precision is improved, but device complexity increases due to A/D conversion requirements
Solution Approach 1:
The patent applies self-service by using the back-EMF generated during the constant conduction ratio period to automatically determine current characteristics. The control unit utilizes the naturally occurring electrical phenomena during the predetermined period without requiring external current sensors or A/D conversion circuits, thereby simplifying the device while maintaining control precision.
Solution Approach 2:
The patent extracts and eliminates the complex A/D conversion and current feedback control circuits from the system. By using open-loop control with constant conduction ratio and leveraging back-EMF measurements, the invention removes the need for current detection circuits and A/D converters, significantly reducing device complexity.
3Manufacturing precision
If toothless winding configuration is used, then manufacturing precision is improved, but inductance decreases leading to control difficulties
Solution Approach 1:
The patent applies dynamics by making the conduction ratio controllable and adjustable during operation. The control unit dynamically sets the conduction ratio to a constant value for a predetermined period, adapting the control strategy to compensate for the low inductance characteristic of toothless windings, thereby maintaining control stability.
Solution Approach 2:
The patent changes the control parameters (conduction ratio and its duration) to match the low inductance characteristics of toothless windings. By extending the constant conduction ratio period to 120-180 electrical degrees, the system compensates for the reduced inductance and maintains reliable control.
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 enables stable rotation control and minimizes current pulsation, reducing noise and vibration while maintaining efficient torque performance, even with high-frequency switching, by avoiding the need for current feedback control and A/D conversion.
Implementation Method 1
a multiphase stator winding provided with conductor portions arranged in positions facing the rotor at predetermined intervals
Data Source
AI summary
A control apparatus of a rotary electric machine includes a rotor; a stator including a multiphase stator winding provided with conductor portions arranged in a circumferential direction thereof. The rotary electric machine is configured of any one of a first configuration having a first inter-conductor member using a magnetic material; a second configuration having a second inter-conductor member using a non-magnetic material; and a third configuration having no inter-conductor member. The control apparatus includes: a drive circuit with switching elements provided for each phase, supplying power to the multiphase stator winding; and a control unit controlling the drive circuit such that a period where a conduction ratio of the switching elements for one phase in the drive circuit is maintained at a constant value is more than or equal to 120 degrees and less than 180 degrees in electrical angle.