Harmonic Current Injection for Torque Enhancement in Permanent Magnet Motors
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Solution Overview
Problem
Current permanent magnet motors face challenges in increasing torque without increasing device size, particularly due to the influence of induced voltage on power supply and the generation of undesirable third-order harmonic magnetic fields which affect torque efficiency.
Innovation Solution
A drive system for rotating electric machines that includes a rotor with permanent magnets and a salient pole portion, along with a stator winding and an inverter system, where the control unit manages energization to generate a fundamental wave current synchronized with rotor speed and a harmonic current that triples the frequency, creating a stator magnetic field with a specified phase relative to the third-order magnetic field of the rotor, effectively extracting the energy of the third-order harmonic as axial torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnet motors are designed to increase energy density in limited mounting space, then power output is improved, but third-order harmonic magnetic fields are generated which reduce torque efficiency
Solution Approach 1:
The patent converts the harmful third-order harmonic magnetic fields into beneficial torque by injecting third-order harmonic currents into the stator windings. The control unit detects the third-order magnetic field components generated by the permanent magnets and generates corresponding harmonic currents that create a stator magnetic field interacting with the rotor's third-order field to produce additional axial torque, thereby transforming the harmful harmonic effects into useful mechanical output.
Solution Approach 2:
The patent changes the electrical parameters by injecting third-order harmonic currents (triple the fundamental frequency) into the stator windings. This parameter change allows the stator magnetic field to synchronize with and interact with the rotor's third-order magnetic field, enabling torque generation from previously harmful harmonic components without altering the physical structure or permanent magnet configuration.
2Use of energy by moving object
If induced voltage is reduced to improve current flow, then power supply influence is decreased, but torque production capability is limited
Solution Approach 1:
The patent maintains continuous useful action by simultaneously utilizing both the fundamental frequency current for basic torque production and the third-order harmonic current for additional torque enhancement. The control unit continuously detects and compensates for induced voltage effects while injecting harmonic currents, ensuring uninterrupted and optimized torque generation across varying operating conditions without sacrificing current flow capability.
Solution Approach 2:
The patent employs a composite approach by combining fundamental frequency currents and third-order harmonic currents in the stator windings. This composite current strategy creates a combined magnetic field that leverages both the primary electromagnetic interaction and the harmonic field interaction, enabling enhanced torque production while managing induced voltage effects through the synergistic action of multiple current components.
3Force
If device size is increased to generate more torque, then torque output is improved, but mounting space requirements increase
Solution Approach 1:
The patent substitutes mechanical enlargement with electromagnetic control by using third-order harmonic current injection to generate additional torque. Instead of increasing the physical size of the motor, permanent magnets, or stator structure, the solution replaces mechanical scaling with electrical control strategies that exploit harmonic field interactions, thereby achieving higher torque output within the same mounting space constraints.
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 torque production by harnessing the energy of the third-order harmonic magnetic field without enlarging the device, allowing for efficient powered running and power generation operations through precise phase control of the harmonic current.
Implementation Method 1
a rotor having one magnetic pole configured by a plurality of permanent magnets... a salient pole portion that is magnetically convex in a radial direction... to generate a stator magnetic field... effectively extracting the energy of the third-order harmonic as axial torque
Data Source
AI summary
A rotating electric machine drive system includes: a rotating electric machine equipped with: a rotor having one magnetic pole configured by permanent magnets, and a salient pole portion that is magnetically convex in a radial direction; and a stator wound with a multiphase stator winding; an inverter for supplying electric power to the stator winding; and a control unit for controlling energization current of the inverters. The control unit performs energization control of the stator winding such that a fundamental wave current at a fundamental frequency synchronized with a rotational speed of the rotor, and a harmonic current that is triple the fundamental frequency flow in the stator winding, and such that energization of the harmonic current generates a stator magnetic field having a specified lead phase or delay phase with respect to a third-order magnetic field of the rotor.