Dual-End Inverter Layout for Low-Voltage Multipole Drives
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Solution Overview
Problem
Low-voltage multipole electric drives face challenges with high current requirements, leading to increased cable losses and the need for complex wiring, particularly due to the requirement of high secondary current ratings in transformers, which complicates the design and offsets the advantages of reduced motor size.
Innovation Solution
The implementation of an electric drive design with inverters arranged at both axial ends of the stator, utilizing half-bridges and capacitor series to form field conductor terminals, reducing the need for wiring by connecting only the DC link across the stator, and using a multi-winding transformer with AC/DC converters to manage high current requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If low voltage supply is used for multipole motor, then motor size is reduced, but cable losses increase and transformer complexity increases
Solution Approach 1:
The motor is divided into multiple independent pole groups, each with its own inverter. This segmentation allows each pole group to operate independently with optimized current paths, reducing the overall current requirement in the main cables and minimizing cable losses while maintaining the compact low-voltage design
2Volume of moving object
If low voltage supply is used for multipole motor, then motor size is reduced, but transformer secondary current rating increases
Solution Approach 1:
The transformer and power conversion system are segmented into multiple independent inverter modules, each handling a specific pole group. This modular approach distributes the current rating requirements across multiple smaller units rather than requiring one large high-current transformer, reducing overall complexity
Solution Approach 2:
The system transitions from a single-phase high-current approach to a multi-phase distributed architecture. By utilizing multiple independent inverter modules operating in parallel, the system transforms the current handling requirement from a single high-current path to multiple lower-current paths, effectively reducing transformer complexity
3Ease of operation
If neutral points are connected back to DC link, then pole groups can be connected in series, but wiring amount increases
Solution Approach 1:
The neutral point connection requirement is extracted and eliminated by using isolated inverter modules for each pole group. Each inverter has its own independent DC link, removing the need for neutral point connections back to the main DC link and significantly reducing the wiring amount while maintaining the series connection capability of pole groups
4Power
If high current rating is required, then low voltage supply can be used, but cable losses increase
Solution Approach 1:
The high current requirement is segmented across multiple independent inverter modules, each handling a portion of the total power. This distribution reduces the current in each individual cable path, minimizing I²R losses while maintaining the overall high power output capability of the system
Solution Approach 2:
The system transitions from a single high-current path to multiple parallel current paths through the modular inverter architecture. This dimensional change in the current distribution topology reduces cable losses by spreading the current load across multiple conductors with lower individual current ratings
Data Source
AI summary
Various embodiments of the teachings herein include an electric drive comprising: a rotor; a stator having a plurality of field conductors for generating a magnetic field to convey a torque to the rotor; one or more inverters arranged at a first axial end of the stator and each comprising two DC terminals and two field conductor terminals, wherein each field conductor terminal is connected to a first terminal of one or more of the field conductors; and one or more second inverters arranged at a second axial end of the stator and each comprising two DC terminals and two second field conductor terminals, wherein each second field conductor terminal is connected to a second terminal of one or more of the field conductors.