AC Machine Pole and Winding Switching for Hybrid Propulsion Torque
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Solution Overview
Problem
Conventional electric motors struggle to provide sufficient torque at both low and high speeds above rated conditions without increasing machine size or weight, limiting their performance in hybrid and electric propulsion systems.
Innovation Solution
A multiphase electric machine that changes the number of poles and series turns per phase belt using electronic switches, allowing operation at higher speeds and torques by switching between series and parallel connections, and adjusting frequency, enabling (V·p/f·N) control to compensate for flux weakening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electric motors operate above rated speed using (V/f) control, then speed increases, but torque decreases
Solution Approach 1:
The patent changes the physical parameters of the machine by switching between different pole configurations (e.g., 4-pole to 2-pole) and changing winding connections (series to parallel). This allows the motor to operate at speeds above rated speed while maintaining or increasing torque output, directly resolving the contradiction between speed increase and torque decrease in conventional (V/f) control
2Force
If electric motors provide multiple of rated torque for starting, then smooth start-up is guaranteed, but machine size and weight increase
Solution Approach 1:
The patent employs dynamic switching of pole configurations and winding connections during operation. For starting, the motor switches to a high-pole configuration with series winding connections to provide multiple of rated torque. During normal operation, it switches to low-pole configuration with parallel connections. This dynamic adaptation allows high starting torque without requiring the machine to be permanently oversized
Solution Approach 2:
The motor design incorporates multiple pole configurations and winding connection methods within a single machine, making it universally capable of providing both high starting torque and efficient continuous operation. This multi-functionality eliminates the need for separate starting mechanisms or oversized design
3Force
If electric motors provide increased torque at higher speeds, then dynamic performance improves, but machine complexity increases
Solution Approach 1:
The control system dynamically switches between different pole configurations and winding connections based on operating conditions. This dynamic control allows the motor to provide increased acceleration torque at higher speeds by switching to appropriate configurations, while keeping the control logic relatively simple through predefined switching sequences
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 increased torque and power output up to twice the rated values, achieving speeds six times the base speed without mechanical gears, improving efficiency and reducing weight and space requirements.
Implementation Method 1
A multiphase inductance-changing and pole-changing electric machine operable at above rated parameters may have a stator having a plurality of phase belts, wherein each phase belt comprises two or more coils, a rotor driven by currents in the stator
Implementation Method 2
decreasing the number of poles may be accomplished by switching the series connections between phase belts to parallel connections
Data Source
AI summary
The machine in accordance with the present disclosure is an AC machine whose pole numbers can be switched (from pole p1 to pole p2), and whose number of series turns per phase N can be switched say from N0=Nrated to N1=N0/2. Furthermore, it employs an inverter so that the frequency can be changed from a low value (e.g., 5 Hz) to a high value (e.g., 200 Hz). Due to the combination of pole number and number of series turns switching/reconfiguration, a high torque at low speed (e.g., 0 rpm) and a high torque at high speed (e.g., 5,000 rpm) can be achieved, making mechanical gears obsolete. In addition, the output power of the motor can be increased at high speed in direct proportion to the speed increase.