Field Winding Rotating Machine Resonant Excitation Control
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Solution Overview
Problem
Conventional field winding type rotating electric machines face challenges in inducing excitation current in the rotor field winding due to high impedance, leading to increased torque ripple, which is difficult to control effectively.
Innovation Solution
The implementation of a capacitor connected between the rectifying element and the rotor field winding, along with a control circuit that superimposes harmonic components on the fundamental components supplied to the stator armature winding, creating a resonant relationship between the inductance of the rotor field winding and the capacitance of the capacitor to lower impedance and improve excitation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rectifying element is connected to both ends of the rotor field winding to enable unidirectional current flow, then field poles can be formed in a predetermined direction, but the impedance of the rotor field winding becomes high making it difficult to induce excitation current
Solution Approach 1:
A capacitor is introduced as an intermediary element connected between the rectifying element and one end of the rotor field winding. This capacitor mediates the electrical connection, allowing excitation current to be induced more effectively while maintaining the unidirectional current flow necessary for field pole formation. The capacitor acts as a bridge that overcomes the high impedance barrier without compromising the rectification function.
Solution Approach 2:
The impedance characteristics of the rotor field winding circuit are modified by adding the capacitor, which changes the overall electrical parameters of the field winding circuit. This parameter change enables better current induction while maintaining the necessary current directionality for reliable field pole formation.
2Power
If excitation current is induced in the rotor field winding to form field poles, then rotational torque can be generated, but torque ripple increases and becomes difficult to control
Solution Approach 1:
The control circuit monitors the excitation current and adjusts the harmonic components supplied to the stator armature winding based on the actual excitation state of the rotor field winding. This feedback mechanism allows the system to maintain stable torque output by dynamically adjusting the excitation current to compensate for variations that would otherwise cause torque ripple.
Solution Approach 2:
Harmonic components with specific frequencies are periodically supplied to the stator armature winding to induce corresponding excitation currents in the rotor field winding. By carefully selecting the frequency and amplitude of these periodic harmonic components, the system achieves stable excitation that minimizes torque ripple while maintaining effective rotational torque generation.
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 configuration facilitates the flow of field current in the rotor field winding, reducing torque ripple and enhancing the excitation performance by adjusting the amplitude and frequency of the harmonic components, thereby improving rotational torque generation.
Implementation Method 1
an inductance of the rotor field winding and a capacitance of the capacitor are in a resonant relationship with a frequency of the harmonic component
Implementation Method 2
supply electric current, which includes a fundamental component for generating rotational torque and a harmonic component having a shorter period than the fundamental component and superimposed on the fundamental component, to the stator armature winding and thereby induce excitation current in the rotor field winding
Implementation Method 3
a rectifying element connected to both ends of the rotor field winding; electric current flows only in one direction in the rotor field winding even when the excitation magnetic flux fluctuates to cause an AC voltage to be generated in the rotor field winding
Data Source
AI summary
A field winding type rotating electric machine includes: a stator armature winding wound on a stator core; a rotor field winding wound on a rotor core; a rectifying element connected to both ends of the rotor field winding; a capacitor having one end connected to one end of the rectifying element and the other end connected between the two ends of the rotor field winding; and a control circuit configured to supply electric current, which includes a fundamental component for generating rotational torque and a harmonic component having a shorter period than the fundamental component and superimposed on the fundamental component, to the stator armature winding and thereby induce excitation current in the rotor field winding. Moreover, an inductance of the rotor field winding and a capacitance of the capacitor are in a resonant relationship with a frequency of the harmonic component.