Motor Control Apparatus Voltage Sag Torque Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor manufacturing devices, motor control systems face challenges in maintaining operation during momentary power interruptions or voltage sags, leading to potential motor stoppages due to overspeed alarms when power is restored.
Innovation Solution
A motor control apparatus with a torque limiter that limits torque during voltage sag and a speed limiter that adjusts speed upon torque limitation cancellation, preventing overspeed and ensuring continuous operation by controlling the motor's speed and torque commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque limitation is applied during power supply voltage sag, then the motor can operate continuously without stopping, but the motor cannot follow the positional command and positional deviation increases
Solution Approach 1:
The speed limiter is activated in advance when torque limitation is detected, preparing the system to handle the upcoming power restoration event. By pre-limiting the speed command based on the accumulated positional deviation, the system prevents overspeed conditions before they occur during voltage sag recovery.
Solution Approach 2:
The controller continuously monitors both the torque command and positional deviation, using this feedback to dynamically adjust the speed limitation. When torque limitation is applied, the system measures the resulting positional deviation and uses this information to set appropriate speed limits during power restoration, ensuring accurate positional control while preventing overspeed.
2Reliability
If torque limitation is applied during power supply voltage sag, then the motor can operate continuously without stopping, but overshooting may occur and the motor may stop due to overspeed alarm upon power restoration
Solution Approach 1:
The speed limiter applies a counteracting force to the speed command in advance of the power restoration event. By detecting torque limitation conditions and pre-limiting the speed command, the system counteracts the tendency toward overspeed and overshooting that would otherwise occur when power is restored, preventing the harmful overspeed alarm condition before it can develop.
3Manufacturing precision
If speed command is increased to compensate for positional deviation after torque limitation, then the motor can recover position, but overspeed may occur causing motor stoppage
Solution Approach 1:
Instead of allowing the speed command to increase freely to compensate for positional deviation, the speed limiter is activated in advance to pre-control the rate of speed increase. This preliminary action ensures that position recovery occurs at a controlled rate that prevents overspeed conditions while still achieving the desired positional accuracy.
Solution Approach 2:
The speed limitation is dynamically adjusted based on the actual motor speed and positional deviation. The controller continuously adapts the speed limit command to balance position recovery needs with overspeed prevention, creating a dynamic control strategy that optimizes both positional accuracy and speed safety during and after torque limitation events.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
[Problem to be solved] To prevent motors from stopping due to, for example, occurrence of an overspeed alarm at the time of restoration of a main circuit power supply voltage. [Solution] A controller 6 includes a torque limiter 17 that starts first torque limitation which limits a commanded torque based on a torque command Tr to a first torque or less in the case where a voltage detector 5 detects that a DC voltage falls below a predetermined voltage, and cancels the first torque limitation in the case where the voltage detector 5 detects that the DC voltage exceeds the predetermined voltage, and a speed limiter 15 that limits a commanded speed based on a speed command Vr to a first speed or less in the case where the torque limiter 17 cancels the first torque limitation.