Externally Excited Synchronous Motor Field Control Without HV Converter
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Solution Overview
Problem
Existing synchronous electric machines require high voltage converters for field excitation, which are financially expensive, complex, and increase electric losses.
Innovation Solution
An electric drive system that eliminates the high voltage converter by electrically coupling a field winding between the node of three-phase armature windings and a center tap terminal of a high voltage bus, using an inverter to control field current through transistors for efficient torque generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high voltage converter is used to provide external excitation to the field winding, then the synchronous electric machine can achieve high efficiency and power output at low speeds, but the system becomes financially expensive, complex, and experiences increased electric losses
Solution Approach 1:
The patent merges the field excitation function with the armature winding circuit by coupling the field winding between the armature winding node and the center tap terminal. This integration eliminates the need for a separate high voltage converter, reducing system complexity while maintaining the synchronous electric machine's high power output capability at low speeds
Solution Approach 2:
The inverter is designed to perform multiple functions: it controls both the armature windings for torque generation and the field winding for excitation. By making the inverter universal, the system eliminates dedicated field voltage control circuitry while preserving the ability to deliver high power output
2Ease of operation
If a high voltage converter is used to provide external excitation, then field control is achieved, but financial expense and system complexity increase
Solution Approach 1:
The field control function is merged into the inverter's control capabilities. The inverter controls field current by switching transistors that regulate current flow through the field winding, eliminating the need for separate field voltage control circuitry and reducing overall system complexity while maintaining ease of field control
Solution Approach 2:
The system uses its own inverter and switching transistors to provide field excitation control without external dedicated circuitry. The inverter serves itself by using its existing components to control both armature and field currents, reducing the need for additional control systems
3Use of energy by moving object
If a separate field voltage control circuit is used, then field excitation is provided, but electric power losses increase
Solution Approach 1:
By merging the field excitation circuit with the armature winding circuit through the inverter, the system eliminates redundant power conversion stages. The inverter directly controls field current from the DC bus without intermediate conversion, reducing electric power losses while maintaining energy efficiency
Solution Approach 2:
The patent extracts the field voltage control function from a separate high voltage converter and integrates it into the inverter circuit. This extraction eliminates the need for separate power conversion equipment, reducing electric power losses associated with additional conversion stages
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 reduces financial expense, system complexity, and electric power losses while providing efficient field excitation without a separate field voltage control circuit.
Implementation Method 1
The synchronous electric machine provides high efficiency and power output at low speeds. The rotor of the synchronous electric machine includes a field winding that is externally excited
Implementation Method 2
transistors of an inverter may be switched to control current flow through the field winding and to control armature current so that a desired or requested driver demand torque may be provided via an electric machine
Data Source
AI summary
An electric drive system is disclosed. In one example, the drive system includes a field winding that is electrically coupled to a high voltage bus without any intervening electrical components. Current flow through the field winding is adjusted via adjusting operation of transistors of an inverter so that a magnetic field and electric machine torque may be controlled.