Magnetic Bearing Current Control for Compressor Stability
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Solution Overview
Problem
Magnetic bearing systems face destabilization due to unbalanced attraction forces, which affect the levitation control of objects, particularly in compressors where precise non-contact support is crucial.
Innovation Solution
A magnetic bearing device with a controller that adjusts the current flowing through first and second electromagnets based on displacement and a correction coefficient, using specific equations to control the composite electromagnetic force, thereby stabilizing levitation control by adjusting the force acting on the object.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current control (push-pull current + fixed current) is used in magnetic bearing, then the electromagnets operate in linear area, but unbalanced attraction force causes destabilization of levitation control
Solution Approach 1:
The patent modifies the current control parameters by introducing a correction coefficient α into the current calculation equations. The first current i1 and second current i2 are calculated as: i1 = (ib + id) / (1 - αx/g0) and i2 = (ib - id) / (1 + αx/g0), where ib is bias current, id is control current, x is displacement, g0 is reference gap length, and α is correction coefficient. This parameter change compensates for the unbalanced attraction force and stabilizes levitation control.
2Measurement precision
If the object to be supported is positioned at center between electromagnets, then gap length is uniform, but any displacement creates unbalanced force affecting control accuracy
Solution Approach 1:
The patent applies preliminary anti-action by pre-calculating and compensating for the unbalanced attraction force through the correction coefficient α in the current control equations. Before displacement occurs, the control system prepares correction factors that counteract the expected unbalanced force, thereby maintaining control accuracy even when the object displaces from the center position.
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 effectively prevents or reduces destabilization of levitation control by adjusting the force acting on the object, improving the operating efficiency of compressors by maintaining stable non-contact support of the rotary shaft.
Implementation Method 1
supports the object to be supported in a noncontact manner by means of a composite electromagnetic force of the first and second electromagnets
Data Source
AI summary
A magnetic bearing supports an object to be supported in a noncontact manner by means of a composite electromagnetic force of first and second electromagnets. A processor-based controller causes a first current and a second current to be controlled according to the following equations,i1=g0-axg0(ib+id)(1)i2=g0+axg0(ib-id)(2)where i1 is the first current flowing to the first electromagnet, i2 is the second current flowing to the second electromagnet, id is a control current, ib is a bias current, g0 is a reference gap length, x is a displacement amount of the object to be supported with respect to a center position, and a is a predetermined correction coefficient.