Segmented Long-Stator Linear Motor With Mid-Point Voltage Balancing
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Solution Overview
Problem
Long stator linear electric motors face inefficiencies and high manufacturing costs due to high impedance, requiring high voltage power converters and resulting in low efficiency and complex voltage balancing issues, especially in applications like train and tram driving systems.
Innovation Solution
A linear electric motor design featuring a stator segmented into multiple units with pairs of multi-level inverters connected via a mid-point bridge, allowing for efficient power distribution and voltage balancing through alternating coil connections and switch management, reducing voltage oscillations and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a long stator linear motor is used to drive vehicles along tracks, then the driving performance is improved, but the impedance increases leading to high manufacturing costs and low efficiency
Solution Approach 1:
The long stator is divided into multiple segments, each with its own inverter. This segmentation allows the system to achieve high power output over long distances while using standard, cost-effective inverter modules rather than requiring a single expensive high-voltage converter
Solution Approach 2:
Multiple inverters are used to power different segments of the stator, with each inverter capable of operating independently. This universal approach allows the same inverter design to be reused across multiple segments, reducing overall system cost and improving manufacturing efficiency
2Power
If a long stator linear motor is used to drive vehicles along tracks, then the driving performance is improved, but the efficiency decreases due to high reactive power requirements
Solution Approach 1:
By segmenting the long stator into multiple shorter sections, each section's inverter operates with lower reactive power requirements. This reduces energy losses in each segment compared to a single long stator operating at high reactive power
Solution Approach 2:
Multiple inverters operate simultaneously to provide continuous thrust along the entire stator length, ensuring that the mobile element receives continuous useful action without the energy losses associated with long-distance power transmission in a single high-impedance system
3Reliability
If multiple inverters are used to power consecutive segments, then the power delivery continuity is improved, but the system complexity increases
Solution Approach 1:
The stator is segmented into sections that can be independently controlled by separate inverters. This allows for continuous power delivery as the mobile element moves between segments, while each inverter remains a manageable, standardized component rather than a single complex high-voltage system
Solution Approach 2:
The system dynamically switches between different inverter segments as the mobile element moves along the track. This dynamic operation ensures continuous power delivery while allowing each inverter to operate within its optimal performance range, reducing overall system complexity
4Loss of energy
If multi-level inverters are used for high-power applications, then the efficiency is improved, but the voltage balancing becomes more challenging
Solution Approach 1:
By dividing the long stator into multiple segments each powered by separate multi-level inverters, the voltage balancing problem is localized to each inverter rather than affecting the entire system. Each inverter can maintain its own DC voltage balance independently, reducing overall complexity
Solution Approach 2:
The segmented architecture acts as an intermediary that isolates the voltage balancing requirements of each inverter. Instead of one complex voltage balancing system for the entire long stator, multiple simpler balancing systems operate independently on each segment
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 solution enhances power efficiency, reduces manufacturing costs, and simplifies the drive system by minimizing voltage variations and power losses, making it more robust and reliable for long stator applications.
Implementation Method 1
each drive unit comprising a DC input circuit section and a multi-level inverter connected to the DC voltage source via the DC input section
Implementation Method 2
The mid-point of the first multi-level inverter is connected via a bridge connection to the mid-point of the second multi-level inverter such that the mid-points of the first and second multilevel inverters are at a common electric potential
Implementation Method 3
A linear electric motor has a higher impedance than a shorter stator and leads to various technical problems in the design of the drive system
Data Source
AI summary
Linear electric motor comprising a stator comprising a plurality of stator segments and a drive system comprising at least one pair of drive units, a first drive unit of said pair connected to a first stator segment and a second drive unit of said pair connected to a second stator segment adjacent the first stator segment, the drive units connected to a DC voltage source, each drive unit comprising a DC input circuit section and a multi-level inverter connected to the DC voltage source via the DC input section, the multi-level inverter comprising a multiphase output connected to coils of the corresponding stator segment. The DC circuit section of the drive units comprises at least two link capacitors (C1, C2) connected between a positive and a negative voltage supply line (V+, V−) and having a mid-point therebetween.