Magnetic bearing compressor protection
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Solution Overview
Problem
In vapor compression systems, the rotating shaft of a shutdown compressor can continue to rotate due to pressure from an operational compressor, potentially damaging the touchdown bearings if they are engaged while still spinning, and traditional check valves may fail to prevent this, leading to bearing damage.
Innovation Solution
A method and system where a controller monitors the rotational speed of the shaft and maintains the magnetic bearing in an active mode for a preset time after shutdown, switching to inactive mode when the speed reaches a threshold, and activates an alarm or closes an isolation valve if the speed does not decrease, thereby preventing the shaft from being placed on touchdown bearings while still rotating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If check valves are used to prevent pressure from causing the rotating shaft to continue rotating after shutdown, then the reliability of preventing shaft rotation is improved, but the device complexity increases and the check valves may fail
Solution Approach 1:
The patent extracts the essential function of the check valve (preventing backflow and shaft rotation) and implements it through control logic in the controller rather than a physical mechanical component. The controller monitors compressor shutdown status and actively prevents shaft rotation through electronic control, eliminating the need for physical check valves and reducing device complexity while maintaining reliability.
Solution Approach 2:
The patent replaces the mechanical check valve system with an electronic control system. The controller uses electronic sensors and control signals to monitor and prevent shaft rotation after shutdown, substituting mechanical components with electronic/magnetic systems that offer more reliable control and fewer failure points.
2Reliability
If the magnetic bearing is kept active for a preset time after shutdown, then the protection of the touchdown bearings is improved, but the energy consumption increases
Solution Approach 1:
The patent applies preliminary action by keeping the magnetic bearing active for a predetermined time period after compressor shutdown is detected. This ensures the shaft is fully stopped before the magnetic bearing is deactivated and the shaft contacts the touchdown bearings, preventing damage. The preset time is optimized to provide adequate protection while minimizing unnecessary energy consumption.
Solution Approach 2:
The patent implements dynamic control of the magnetic bearing, transitioning it from active to inactive state based on real-time shaft rotation status and time elapsed since shutdown. This dynamic approach allows the system to maintain protection only when necessary (when shaft is still rotating) and reduce energy consumption when the shaft has stopped, rather than maintaining a static active/inactive state.
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 effectively prevents the rotating shaft of a shutdown compressor from being placed on touchdown bearings while still rotating, mitigating the risk of damage and ensuring the system operates safely and efficiently by reducing reliance on check valves.
Implementation Method 1
magnetic bearings may be used to levitate the rotating shaft while the compressor is operational
Data Source
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AI summary
A vapor compression system (800) and method (900) for operating the vapor compression system (800) are provided. The vapor compression system (800) includes a first compressor (100), a second compressor (200), a condenser (500), and at least one check valve (150, 250) disposed between the first compressor (100) and the condenser (500). The method provides for the transmitting of a shutdown command to at least one of the first compressor (100) and the second compressor (200), at least one of the first compressor (100) and the second compressor (200) including a rotating shaft (140) and a magnetic bearing (110), the magnetic bearing (110) having an active mode and an inactive mode, the magnetic bearing (110) levitating the rotating shaft (140) in the active mode. The method further provides for the monitoring of at least one of a rotational speed of the rotating shaft (140) and a differential pressure over the check valve (150, 250) for a preset time, wherein the magnetic bearing (110) remains in the active mode at least during the preset time.