Dual Electric Machine Drive System Torque Management
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Solution Overview
Problem
Existing drive systems for land crafts, such as electric vehicles, face challenges in achieving efficient torque and power delivery while minimizing the demands on power electronics, particularly due to the high voltage and current requirements of permanent-magnet machines, which lead to increased costs and complexity.
Innovation Solution
A drive system utilizing multiple electric machines, such as a combination of permanent-magnet and reluctance machines, where one machine operates in both low and high torque ranges and the other is optimized for specific operational ranges, allowing for efficient torque delivery with reduced power electronics demands by switching off machines when not needed, thereby minimizing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a permanent-magnet machine is used to provide high torque per weight, then the drive system achieves high efficiency and compactness, but the power electronics requirements increase significantly due to high voltage and current demands
Solution Approach 1:
The drive system is segmented into two separate electric machines: a first machine (permanent-magnet type) optimized for high torque per weight, and a second machine (reluctance or induction type) optimized for different operational characteristics. This segmentation allows each machine to operate in its optimal efficiency range while reducing the peak power requirements for the power electronics, as the machines can share the power delivery burden rather than one machine requiring peak performance across all conditions.
2Power
If the power electronics are designed to handle maximum voltage and current simultaneously, then the drive system can meet peak power demands, but the cost and complexity increase due to over-installation
Solution Approach 1:
The control device dynamically manages the operation of the two electric machines based on real-time power demands. By switching between different machine combinations and operating modes, the system adapts to varying load conditions, ensuring that the power electronics only need to handle the actual instantaneous power requirements rather than being oversized for peak corner power conditions. This dynamic operation reduces the required power electronics capacity while maintaining peak performance capability.
3Device complexity
If a single electric machine operates across all speed ranges, then the system is simpler, but efficiency decreases due to operating outside optimal ranges
Solution Approach 1:
Each electric machine is locally optimized for specific operational characteristics: the first permanent-magnet machine is optimized for high torque production at lower speeds, while the second machine (reluctance or induction type) is optimized for different speed and torque ranges. The control device selectively activates each machine based on the current operating conditions, ensuring that whichever machine is active is operating in its optimal efficiency range, thereby minimizing energy losses across the entire operating spectrum.
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 enhances the efficiency and reduces the power electronics' demands, achieving a hyperbolic torque-speed characteristic with improved compactness and efficiency, while minimizing energy losses and costs.
Implementation Method 1
a first electric machine M1 and a second electric machine M2, which both act on common drive shaft S as motors for driving the land craft
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E
AI summary
A drive system (DS) for a land craft comprises a machine system (M1, M2) for driving the land craft, the machine system comprising at least a first and a second electric machine (M1, M2) acting on a common drive shaft (S) for driving the land craft, and a control device (PE, PE1, PE2) which is adapted to control the machine system for operating in at least two rotating speed operation ranges (OR1, OR2) with different rotating speeds of the drive shaft (S). The first electric machine (M1) is controlled to operate in both rotating speed operation ranges (OR1, OR2) to provide a first drive torque, and the second electric machine (M2) is controlled to operate in only one of the rotating speed operation ranges (OR1) to provide a second drive torque in addition to the first drive torque.