Variable Air Gap Motor Structure for Counter Electromotive Force Control
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Solution Overview
Problem
Permanent magnet synchronous motors in electric vehicles face increased counter electromotive force at high rotational speeds, leading to efficiency and output decreases due to the need for additional current supply, which is costly and difficult to control in existing motor structures.
Innovation Solution
The motor structure includes a stator support that moves axially within the motor housing, reducing the interlinkage flux area by adjusting the position of the stator relative to the rotor, thereby controlling the counter electromotive force through hydraulic pressure and a gear unit, allowing for variable adjustment of the air gap and interlinkage flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the motor operates at high rotational speed, then the power output increases, but the counter electromotive force increases proportionally causing efficiency decrease
Solution Approach 1:
The patent applies the dynamics principle by making the air gap between stator and rotor variable rather than fixed. The air gap length changes dynamically based on rotational speed: at high speeds, the air gap increases to reduce magnetic flux and counter electromotive force; at low speeds, the air gap decreases to maintain efficient magnetic coupling. This dynamic adjustment resolves the contradiction between maintaining high power output and reducing energy loss from counter electromotive force.
Solution Approach 2:
The patent implements parameter changes by modifying the physical dimension of the air gap length as a function of operational conditions. Specifically, the air gap length parameter is changed from a constant value to a variable parameter that increases with rotational speed. This parameter change directly controls the magnetic flux density and counter electromotive force, allowing the motor to operate efficiently across different speed ranges without sacrificing power output capability.
2Loss of energy
If additional current is supplied to control weak flux, then the counter electromotive force is suppressed, but the manufacturing cost and control complexity increase
Solution Approach 1:
The patent replaces the electrical control method (supplying additional current to control weak flux) with a mechanical method (physically adjusting the air gap length). Instead of using complex electrical control systems to manage magnetic flux, the invention uses a mechanical adjustment mechanism that changes the air gap dimension. This substitution simplifies the control system while achieving the same goal of suppressing counter electromotive force at high speeds.
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 solution effectively reduces counter electromotive force and enhances motor efficiency and output in high rotation regions by inversely proportional reduction of the interlinkage area as rotational speed increases, without the need for additional current supply.
Implementation Method 1
the counter electromotive force is generated in proportion to the rotational speed of the motor due to the magnetic flux produced by the permanent magnet
Implementation Method 2
a motor controller (10) is included to operate a hydraulic pressure supply source (11) capable of varying an air gap length between the stator (3) having an armature coil (13)
Implementation Method 3
increasing the size of the air gap in a high rpm region to reduce the counter electromotive force
Data Source
AI summary
A motor structure for varying a counter electromotive force is provided. The motor structure includes a rotor that is fixed annularly and concentrically to a radially outside from an exterior circumferential surface of a shaft of an electric motor and has a permanent magnet, and a stator that has coils positioned on the interior side of a motor housing and on the concentrically exterior side with the permanent magnet of the rotor. Further, the coils are positioned spaced apart from each other at predetermined intervals. A drive unit moves the stator in the axial direction of the shaft to vary the interlinkage flux, by varying an area that the magnetic flux of the permanent magnet of the rotor passes through the coils of the stator.