Motor Control Device for Induction Motor Flux Amplification
Solution Overview
Problem
Induction motors used in machine tools face challenges with heat generation and responsiveness during light load conditions, particularly when switching between speed control and position control or during acceleration/deceleration, due to magnetic flux weakening, leading to prolonged machining times and stability issues.
Innovation Solution
A motor control device that includes a change detection part to amplify the magnetic flux command or excitation current command, along with adjusting the gain of the operation control part, to quickly increase secondary magnetic flux during mode switching or acceleration, thereby reducing heat generation and improving responsiveness and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If magnetic flux weakening technology is used to reduce heat generation during light load, then heat generation is reduced, but responsiveness of position control and acceleration/deceleration declines due to insufficient torque
Solution Approach 1:
The magnetic flux command is made dynamically adjustable based on operational conditions. During light load normal operation, reduced magnetic flux is maintained for heat reduction. However, during position control mode or acceleration/deceleration, the magnetic flux command is temporarily increased to ensure sufficient torque and responsiveness, resolving the contradiction between heat reduction and performance requirements
Solution Approach 2:
The magnetic flux command parameter is changed based on operational mode and load conditions. The system switches between different magnetic flux levels: reduced flux during light load speed control for heat reduction, and increased flux during position control or acceleration for high responsiveness, thereby resolving the trade-off between temperature and speed performance
2Speed
If magnetic flux amplification is performed to hasten the rise in secondary magnetic flux, then responsiveness is improved, but transient phenomenon occurs causing the induction motor to move and control stability declines
Solution Approach 1:
The gain of the operation control part is reduced in advance before magnetic flux amplification occurs. This preliminary adjustment prevents excessive transient responses and motor movement that would otherwise occur during flux amplification, thereby maintaining control stability while still achieving the desired responsiveness improvement
Solution Approach 2:
By reducing the control gain beforehand, the system cushions against the potential instability caused by magnetic flux amplification. This preparatory measure absorbs the transient shock and prevents the induction motor from moving during the flux transition, ensuring stable control while achieving fast response
3Stability of the object's composition
If waiting time is introduced to allow magnetic flux to sufficiently rise before operation start, then control stability is maintained, but machining time lengthens
Solution Approach 1:
The magnetic flux command is increased in advance before operation starts. By preparing the magnetic flux level beforehand, the system eliminates the need for waiting time during operation startup, thereby reducing machining time while maintaining control stability through the pre-adjusted flux level
Solution Approach 2:
The system skips the waiting period by rushing through the magnetic flux buildup phase. The magnetic flux command is immediately increased to the required level before operation begins, allowing the system to transition directly into operation without the traditional delay, thus reducing machining time while maintaining stability
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 enables reduced heat generation, enhanced responsiveness, and improved stability during control mode switching and acceleration/deceleration, by temporarily increasing the magnetic flux and adjusting gains, thus expediting operation starts and shortening machining times.
Implementation Method 1
Induction motors have been used as the spindle motor of a machine tool... causes a rotating magnetic field to be generated by flowing excitation current to the stator coil, as well as causing induction current to generate in the rotor, in which the rotor rotates so as to follow the rotation of the rotating magnetic field by way of this electromagnetic force
Implementation Method 2
a magnetic flux amplification part (for example, the magnetic flux amplification part 12 described later) that performs magnetic flux amplification to temporarily increase the excitation current command or a magnetic flux command for generating the excitation current command in the current control part
Data Source
AI summary
A motor control device including: an operation control part that generates a torque command based on an operation command, and controls a rotational position and/or rotational speed of the spindle; a current control part that generates an excitation current command to control secondary magnetic flux of the induction motor, and a torque current command to control torque of the induction motor based on the torque command; a change detection part that detects a change in operation command requiring increasing the secondary magnetic flux of the induction motor; a magnetic flux amplification part that performs magnetic flux amplification to temporarily increase the excitation current command or a magnetic flux command in the current control part, in a case of a change in the operation command being detected; and a gain change part that changes gain of the operation control part when performing magnetic flux amplification.