Vacuum Pump Drive Control for Transient Overload Management
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Solution Overview
Problem
Current vacuum pumping systems in semiconductor processing require high power capacity to handle pump-down operations, leading to increased costs and size, despite this phase only accounting for a small percentage of operation, and existing drive controls risk tripping the motor during overload conditions, potentially damaging wafers.
Innovation Solution
A drive control system that allows the pumping system to operate in transient overload conditions without tripping by monitoring states such as thermal load and adjusting power supply, using gain circuitry to control current and voltage, thereby avoiding operational limits and extending motor performance during high-power demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power capacity of the vacuum pump and drive is increased to meet pump-down requirements, then the pump can handle high power demand during evacuation, but the cost and size of the drive increase significantly
Solution Approach 1:
The drive control system dynamically adjusts motor power based on real-time thermal load monitoring. The system transitions from static rated power operation to dynamic power control, allowing the motor to operate at higher powers during transient pump-down phases while automatically reducing power during steady-state operation to prevent thermal overload.
Solution Approach 2:
The system changes the operational parameters of the motor by allowing transient overload conditions (operating above rated current) during pump-down phases. The drive control modifies current limits and power delivery based on monitored thermal conditions, enabling the motor to deliver higher power when needed without permanent damage.
2Productivity
If the motor is allowed to operate in overload conditions to improve pump-down performance, then higher power can be delivered, but the motor may trip and cause damage to wafers
Solution Approach 1:
The drive control system continuously monitors motor thermal load through current measurement and feedback control. This real-time feedback allows the system to detect thermal conditions and adjust power delivery accordingly, enabling transient overload operation during pump-down while preventing motor tripping through active thermal management.
Solution Approach 2:
The system prepares for potential thermal overload by implementing advance thermal modeling and prediction. The drive control anticipates thermal conditions and adjusts power delivery proactively, cushioning against the risk of motor tripping before it occurs during high-demand pump-down phases.
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 enables improved performance during high-power operations like pump-down without motor tripping, allowing for a less expensive motor/drive assembly and increased torque, reducing pump-down times and preventing overheating, thus enhancing system efficiency and reliability.
Implementation Method 1
The motor can be thermally modelled using the first order system with its temperature being a function of the square of the input current
Implementation Method 2
the motor thermal load (MTL) of the motor. As is known in the art, the motor current (Imotor) is input to the first module, which estimates motor thermal load
Implementation Method 3
The power is controlled by controlling the current supplied to the motor, which in turn is controlled by adjusting the frequency and/or amplitude of the voltage in the motor
Data Source
AI summary
The present invention provides a pumping system (60) comprising: a pumping mechanism (64); a motor (51) for driving the pumping mechanism; a drive control (50) for controlling the motor; and means (52) for monitoring at least one state within the system; wherein, to improve the performance of the system, the drive control causes the system to operate for transient periods in an overload condition which can result in said monitored state exceeding a predetermined operational limit, and when operating in said overload condition said drive control controls the power to the motor dependent on the level of said monitored state thereby avoiding said state from exceeding said operational limit.