Medium-Voltage Drive Assembly With Multi-Winding Torque Optimization
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Solution Overview
Problem
Existing medium voltage variable speed drives (VSD) systems face limitations due to high switching losses in thyristor-based semiconductors, leading to non-optimal motor design, increased system complexity, and higher costs, while the number of poles in electric machines affects torque production, rotor dynamics, and mechanical vibrations, limiting their performance and efficiency.
Innovation Solution
A medium voltage variable speed assembly with a plurality of stator winding systems and converter arrangements using IGBTs or MOSFETs with low nominal voltage, eliminating the need for a block transformer and optimizing the electric machine design by selecting the number of poles and phases to maximize rotor volume and torque production without frequency limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If thyristor-based semiconductors are used in medium voltage VSD systems, then high voltage operation is achieved, but switching losses increase and system complexity increases
Solution Approach 1:
The patent divides the medium voltage power conversion system into multiple low-voltage converter units (e.g., three 1.7kV units for 5.4kV operation). Each unit uses independent IGBT-based converters operating at low voltage with minimal switching losses, eliminating the need for high-voltage thyristors while maintaining medium voltage output capability through series connection of the units.
Solution Approach 2:
Multiple low-voltage converter units are combined in series to achieve medium voltage operation. The individual converter units are electrically connected in series between the motor terminals, allowing their voltages to add up to the required medium voltage level while each unit operates efficiently at low voltage with minimal losses.
2Power
If the number of poles in electric machine is increased, then torque production increases, but rotor bending modes and mechanical vibrations worsen
Solution Approach 1:
The patent changes the electrical parameters by using variable frequency power supply to drive the high-pole-count motor. This allows the motor to operate efficiently at high pole counts for maximum torque while the frequency control compensates for the reduced synchronous speed, and the drive system can adjust operating parameters to avoid resonant frequencies that cause vibrations.
3Power
If rotor diameter and length are maximized to increase torque, then torque production improves, but stator yoke thickness must be minimized
Solution Approach 1:
The patent changes the magnetic flux density parameter by using optimized winding configurations and power electronic control to maintain appropriate flux levels despite reduced yoke thickness. This allows the motor to achieve high torque with compact dimensions by precisely controlling the electromagnetic parameters rather than relying solely on increased physical size.
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 torque production, reduces mechanical stress, and minimizes system complexity and cost by optimizing the electric machine design, allowing for efficient operation across a wide speed range with reduced vibrations and transformer losses.
Implementation Method 1
Each converter unit (82) is a two-level converter unit and comprises a three-phase output electrically connected to exactly one stator winding system (4)
Implementation Method 2
an electric machine (2) comprising six poles and six stator winding systems (4). Each of the stator winding systems (4) is a three-phase system isolated from the ground and from the other stator winding systems (4)
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A medium voltage variable speed assembly comprising an electric machine (2), and a power supply configuration for supplying alternating current power to the electric machine (2). The electric machine comprises a plurality of stator winding systems (4). The power supply configuration comprises a supply converter system (6) having a two-level direct current input (61) and an alternating current output (62) connected to the plurality of stator winding systems (4). The supply converter system (6) comprises a plurality of converter arrangements (8) connected in series such that each of the converter arrangements (8) comprises at least one two-level converter unit having a DC link whose nominal voltage is low enough for IGBTs, MOSFETs or similar components. Characteristics of the electric machine such as a number of machine phases, a number of stator poles, a number of stator winding systems and a number of stator slots are selected in a specific way.