Vacuum Pump Rotor Temperature Calculation via Motor Current
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Solution Overview
Problem
Turbomolecular pumps face challenges in accurately determining the temperature of rotating components like the rotor, especially under varying operating conditions, leading to potential overheating and reduced pump performance due to conservative power limitations.
Innovation Solution
A method using a mathematical function with a correction element to calculate the temperature of monitored components, incorporating measured variables like motor power consumption and thermal models, which accounts for the thermal inertia of components, allowing for more precise and adaptive temperature determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the permissible maximum motor power is determined by calculation and/or experimentally assuming the most unfavorable process conditions, then the pump rotor will not exceed the maximum permissible rotor temperature even under unfavorable conditions, but the output power of the turbomolecular pump is usually limited to a value far below an actually thermally permissible value
Solution Approach 1:
The patent applies dynamics by transitioning from a static, conservative power limitation to a dynamic power control system. The control device continuously monitors actual process conditions (gas type, gas quantity, ambient temperature, cooling conditions) and adjusts the permissible maximum motor power in real-time based on the currently favorable or unfavorable conditions, rather than always operating at the conservative limit determined for worst-case scenarios.
Solution Approach 2:
The patent implements parameter changes by varying the permissible maximum motor power parameter according to actual operating conditions. Instead of maintaining a constant conservative power limit, the system dynamically changes this parameter based on measured process variables, allowing higher power output when conditions are favorable and reducing power when conditions approach unfavorable thresholds.
Solution Approach 3:
The patent employs feedback mechanisms where the control device continuously monitors actual process conditions (gas flow, temperature, pressure) and uses this feedback to adjust the permissible maximum motor power. This closed-loop control allows the system to respond to changing conditions and optimize power utilization while maintaining rotor temperature within safe limits.
2Measurement precision
If direct measurement of the rotor temperature is implemented, then accurate temperature data can be obtained, but the signal transmission from the rapidly rotating pump rotor to the stator is difficult and requires great effort
Solution Approach 1:
The patent uses an intermediary approach by introducing a mathematical model that acts as a mediator between measurable parameters (motor power, ambient temperature, cooling conditions) and the difficult-to-measure rotor temperature. Instead of directly measuring rotor temperature through complex signal transmission, the system calculates it using the mathematical model based on easily measurable parameters, thus avoiding the need for complex temperature sensing and signal transmission systems on the rotating rotor.
Solution Approach 2:
The patent replaces the mechanical/physical temperature measurement system (sensors on the rotating rotor) with a mathematical calculation system. The mathematical model substitutes direct physical measurement with computational estimation based on thermodynamic principles and measurable operating parameters, eliminating the need for complex mechanical signal transmission from the rotating to stationary components.
3Reliability
If the motor power is limited to the specified maximum power to prevent rotor overheating, then the rotor temperature remains below the maximum permissible temperature, but the pump performance is reduced when actual conditions are more favorable than assumed
Solution Approach 1:
The patent applies dynamics by making the motor power limitation adaptive rather than static. The control device dynamically adjusts the permissible maximum motor power based on real-time monitoring of actual process conditions, allowing the pump to operate at higher performance levels when conditions are favorable while maintaining protective limitations when conditions approach unsafe thresholds.
Solution Approach 2:
The patent implements parameter changes by varying the motor power limit parameter according to actual operating conditions. The system changes this parameter from the conservative value determined for worst-case scenarios to a higher value when actual conditions (gas type, gas quantity, cooling efficiency, ambient temperature) are more favorable, thus optimizing pump performance while maintaining safety.
Data Source
AI summary
A mathematical function is used to calculate the temperature of a component (rotor, bearing) of a vacuum pump that is to be monitored. This function takes into account measured temperatures of individual components, such as the pump rotor and stator, or the pump electronics. According to the invention, the function includes a correction element that depends on a measured energy consumption (current, power) of the motor.