Electric Machine Converter Winding Switching to Reduce Current Transients
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Solution Overview
Problem
Traditional electric machine converters face challenges in safely handling high rotation speeds due to unsuppressed back EMF, leading to overvoltage issues, and require higher peak currents and torque when nominal rotation speed is increased, while induction machines struggle with current transients during winding configuration changes.
Innovation Solution
A converter system with a control mechanism that allows stator windings to switch between low-speed and high-speed configurations by limiting torque, deactivating the converter during changes, and maintaining a model of the electric machine to control rotation speed and torque based on stator currents and voltages, reducing current transients and enabling fast configuration changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the nominal rotation speed of a permanent magnet machine is increased to allow higher operating speeds, then the maximum operating speed is improved, but the peak current and steady-state current requirements increase, leading to higher torque and larger AC system design requirements
Solution Approach 1:
The patent applies dynamics by making the winding configuration changeable during operation. Configuration switches allow the stator windings to be reconfigured between low-speed and high-speed connections while the machine is running, enabling adaptive adjustment of the machine characteristics to match operating conditions without requiring oversized components for peak power requirements.
Solution Approach 2:
The patent changes the electrical parameters of the machine by reconfiguring the winding connections. By changing the series/parallel arrangement of stator windings through configuration switches, the machine's inductance, resistance, and back-EMF characteristics are dynamically adjusted to optimize performance for different speed ranges, reducing current requirements at high speeds.
2Adaptability or versatility
If configuration switches are used to change winding connections during operation, then adaptability to different speed ranges is improved, but current transients and operational complexity increase
Solution Approach 1:
The control system performs preliminary actions by predicting when configuration changes should occur based on operating conditions. The controller monitors machine parameters and proactively reconfigures windings before performance degradation occurs, smoothing transitions and avoiding harmful current transients that would result from reactive configuration changes.
Solution Approach 2:
The patent implements feedback control where the controller continuously monitors operating parameters such as speed, current, and torque. Based on this feedback, the controller determines the optimal winding configuration and executes reconfiguration commands, creating a closed-loop system that adapts to changing conditions while maintaining stable operation and minimizing transients.
3Speed
If the number of series connected turns is reduced for high-speed operation, then the back EMF is reduced allowing higher speeds, but the torque capability at high speeds decreases
Solution Approach 1:
The patent applies dynamics by dynamically reconfiguring the winding connections based on operating speed. At high speeds, the system switches to a configuration with fewer series turns to reduce back-EMF and enable higher speed operation. The controller dynamically adjusts the configuration switches to match the optimal winding arrangement for the current operating point, maintaining torque capability across the full speed range.
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 safe operation at higher speeds without overvoltage risks, maintains higher torque limits in low-speed configurations, and allows rapid switching between configurations, similar to a mechanical gearbox, reducing current transients and operational losses.
Implementation Method 1
a converter stage (102) configured to supply stator voltages to the stator windings
Implementation Method 2
The control system is configured to limit torque of the electric machine so that a torque limit is higher when the stator windings are in the low-speed configuration than when the stator windings are in the high-speed configuration
Implementation Method 3
an electric machine (105) whose stator windings are changeable to be in a low-speed configuration or in a high-speed configuration
Data Source
Figure 1a
Figure 1b~1c
Figure 2
AI summary
The disclosure relates to a converter (101) for driving an electric machine whose stator windings are changeable to be in a low-speed configuration or in a high-speed configuration having less series connected turns than the low-speed configuration. The converter comprises a converter stage (102) for supplying stator voltages to the stator windings, and a control system (103) that controls the stator windings to be in the low-speed configuration or in the high-speed configuration. The control system deactivates the converter stage during a change between the low-speed configuration and high-speed configuration and limits torque of the electric machine so that a torque limit is higher when the stator windings are in the low-speed configuration than when the stator windings are in the high-speed configuration. As the torque limit is changed when the number of series connected turns of the stator windings is changed, unwanted current transients can be reduced.