Electric Machine Winding Control with Variable Freewheel Angle
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As the permanent-magnet rotor of an electric machine rotates, it induces a back emf that increases with speed, making it difficult to drive current and power into the machine, leading to inefficiencies and control challenges, especially as the back emf exceeds the excitation voltage, causing current spikes and reducing torque.
Innovation Solution
The method involves sequentially exciting and freewheeling the winding of the electric machine, varying the freewheel angle in response to changes in excitation voltage and speed, to maintain constant power and efficiency across a range of voltages, using a control system that includes a position sensor, current controller, and inverter to manage current flow and prevent excessive currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the excitation voltage is increased to drive more current into the winding, then the power output increases, but the current spikes when back emf exceeds excitation voltage, reducing reliability
Solution Approach 1:
The patent applies dynamics by making the freewheel angle variable rather than fixed. The control system dynamically adjusts the freewheel angle in response to changes in excitation voltage and back emf conditions. This dynamic adjustment prevents current spikes by adapting the freewheeling period to match the varying electrical conditions, thereby maintaining reliable current control while enabling high power output.
Solution Approach 2:
The patent implements feedback control by monitoring the excitation voltage and back emf conditions, then using this information to adjust the freewheel angle. The control system continuously responds to changing electrical conditions, creating a closed-loop control mechanism that prevents current spikes and maintains stable operation throughout the electrical cycle.
2Loss of energy
If the freewheel angle is increased to improve efficiency in the falling back emf region, then energy loss decreases, but the power output decreases due to shorter current driving period
Solution Approach 1:
The patent resolves this contradiction through dynamic adjustment of the freewheel angle based on real-time electrical conditions. By varying the freewheel angle in response to excitation voltage changes and back emf conditions, the system optimizes the balance between efficiency and power output at different points in the electrical cycle, rather than using a fixed angle that compromises one parameter.
Solution Approach 2:
The patent changes the electrical parameter (freewheel angle) to optimize performance. By adjusting this parameter in response to varying excitation voltage and back emf conditions, the system achieves both low energy loss and high power output across different operating conditions, transforming a static design into an adaptive one.
3Device complexity
If a fixed freewheel angle is used to simplify control, then device complexity decreases, but the ability to maintain constant power over varying voltage ranges is reduced
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed control parameter to a dynamic one. The freewheel angle becomes a variable that automatically adjusts in response to excitation voltage and back emf conditions, enabling the system to maintain constant power output across varying voltage ranges while adding only minimal control complexity through standard feedback mechanisms.
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 allows for efficient control of power and torque, preventing current spikes and maintaining efficiency and constant power output despite changes in excitation voltage and speed, ensuring reliable operation of electric machines like vacuum cleaners powered by battery packs.
Implementation Method 1
As the permanent-magnet rotor of an electric machine rotates, it induces a back emf in a winding of the electric machine
Implementation Method 2
drive current, and thus power, into the electric machine
Data Source
AI summary
A method of controlling an electric machine that includes sequentially exciting and freewheeling a winding of the electric machine. The winding is excited by an excitation voltage and is freewheeled over a freewheel angle. The method then includes varying the freewheel angle in response to changes in the excitation voltage. Additionally, a control system for an electric machine, and a product incorporating the control system and electric machine.