SynRM Powertrain Gear Ratio Control for Extended Constant Power
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Solution Overview
Problem
Synchronous reluctance machines (SynRM) face limitations in providing an extended continuous power region and competitive efficiency due to the absence of field excitation and magnets, making them less attractive compared to wound field synchronous machines (WFSM) or permanent magnet synchronous machines (PMSM).
Innovation Solution
Implementing a multi-geared or continuously variable transmission (CVT) system with a synchronous reluctance machine to enhance the constant power region and increase drive-cycle efficiency by controlling gear ratios, allowing for higher peak torque at low speeds and extended field-weakening regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If synchronous reluctance machine is used without field excitation and magnets, then cost is reduced, but continuous power region and efficiency deteriorate
Solution Approach 1:
The patent applies dynamics by implementing a variable gear ratio transmission system that can continuously adjust the gear ratio based on operating conditions. This allows the SynRM to operate at optimal speeds across a wide range of load conditions, effectively extending the continuous power region without requiring field excitation or magnets, thus maintaining cost advantages while improving power delivery capability
Solution Approach 2:
The patent utilizes parameter changes by varying the gear ratio as a control parameter to optimize the motor speed for different axle torque and power demands. This enables the SynRM to maintain high efficiency across different operating points by adjusting the transmission ratio, compensating for the lack of field excitation control available in PMSM systems
2Device complexity
If synchronous reluctance machine is used without field excitation and magnets, then manufacturing complexity is reduced, but efficiency deteriorates
Solution Approach 1:
The patent implements feedback control by using a controller that receives information about axle torque and power demands, determines optimal gear ratios and motor speeds, and adjusts the transmission system accordingly. This closed-loop control enables the SynRM to operate at peak efficiency points across varying load conditions, compensating for the absence of field excitation control while maintaining simple rotor construction
Solution Approach 2:
The system dynamically adjusts the gear ratio based on real-time operating conditions to keep the SynRM operating in its high-efficiency region. This dynamic adaptation allows the simple, magnet-free rotor design to achieve competitive efficiency by optimizing the operating point through transmission ratio variation rather than through complex rotor structures
3Power
If multi-geared or CVT transmission is implemented with SynRM, then constant power region is extended, but device complexity increases
Solution Approach 1:
The patent applies universality by designing a transmission system that serves multiple functions: it extends the constant power region, optimizes efficiency across operating conditions, and enables the SynRM to compete with more complex machine topologies. The controller also performs multiple functions including determining optimal gear ratios, calculating motor speeds, and coordinating transmission operation, thereby managing the added complexity through integrated 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
The system provides enhanced efficiency and competitive performance by optimizing gear ratios, making SynRM a viable alternative to WFSM and PMSM, particularly suitable for agriculture applications and other vehicles.
Implementation Method 1
Synchronous reluctance machines (SynRM) are a well-established machine architecture that take advantage of a high saliency ratio in the absence of field excitation and/or magnets to generate torque using the reluctance component of the torque equation
Data Source
AI summary
A powertrain system for a vehicle includes a synchronous reluctance machine having a rotor defining a plurality of circumferentially-spaced regions having relatively low reluctance interspaced with regions having relatively high reluctance. A transmission is operatively disposed between the synchronous reluctance machine and one or more wheels. A controller is configured to: determine, for given values of axle torque and output speed, a plurality of different sets of values for a gear ratio of the transmission and for motor speed of the synchronous reluctance machine; determine an optimal set of the plurality of different sets of values for a gear ratio of the transmission and for motor speed of the synchronous reluctance machine; and operate the synchronous reluctance machine and the transmission in accordance with the optimal set of values for a gear ratio of the transmission and for motor speed of the synchronous reluctance machine.