Magnetic bearing control device and control method
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Solution Overview
Problem
Magnetic bearings face challenges in precise control and increased application costs due to complex control circuit structures, particularly in simplifying the full bridge circuit and managing power loss and ripple in coil currents.
Innovation Solution
A control device and method that generates switching control signals to efficiently charge a bootstrap capacitor, adjusting magnetic field intensity and controlling current supply to the bearing coil, thereby simplifying the control circuit structure and reducing power loss by suppressing coil current ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a full bridge circuit structure is used to control the magnetic bearing coil, then the magnetic bearing can be driven with sufficient power, but the control circuit structure becomes complicated and control precision becomes difficult to achieve
Solution Approach 1:
The patent extracts and removes unnecessary components from the full bridge circuit, specifically eliminating the need for four switching elements by using only two switching elements (Q1, Q2) combined with two diodes (D1, D2). This simplification maintains the essential power delivery function while dramatically reducing circuit complexity and control difficulty.
Solution Approach 2:
The simplified circuit design makes each component serve multiple functions. The switching elements and diodes not only control current flow but also inherently provide freewheeling paths and voltage clamping functions that would otherwise require additional components. This multi-functionality achieves full bridge performance with half the component count.
2Measurement precision
If switching elements are used in the control circuit, then precise control of the magnetic bearing is possible, but the circuit structure becomes complicated and application cost increases
Solution Approach 1:
The patent replaces expensive, complex switching elements with simpler diodes in specific circuit positions. The diodes, being passive and inexpensive components, perform sufficient control functions for the magnetic bearing application without requiring complex gate drive circuits or precise timing control, thereby reducing both circuit complexity and cost while maintaining adequate control precision.
3Reliability
If a capacitor is added to secure driving voltage of switching elements, then the switching elements can operate reliably, but the circuit structure becomes more complicated and charging efficiency needs improvement
Solution Approach 1:
The capacitor in the simplified circuit charges and discharges automatically through the natural switching actions of Q1, Q2 and the body diodes of the transistors. The circuit topology itself provides the charging path without requiring external control circuitry or additional active components, making the voltage securing mechanism self-regulating and eliminating the need for complex charging control while maintaining reliable operation.
4Speed
If switching elements are turned on and off rapidly to control the magnetic field, then the magnetic bearing response is fast, but ripple in coil current increases and power loss increases
Solution Approach 1:
The patent converts the potentially harmful effect of rapid switching into a beneficial continuous current flow. By providing dedicated freewheeling paths through diodes D1 and D2, the circuit allows the coil current to continue flowing smoothly during switching transitions, thereby suppressing current ripple and reducing electromagnetic interference and power loss while maintaining fast response capability.
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 efficiently charges the bootstrap capacitor, simplifying the control circuit structure and reducing power loss by limiting coil current supply and suppressing ripple, thereby improving the control of magnetic bearings.
Implementation Method 1
a current passes through a magnetic bearing coil to form a magnetic force, and then a rotor of the motor of the compressor is held aloft using the magnetic force
Implementation Method 2
A capacitor is additionally used to secure a driving voltage of the switching elements
Data Source
AI summary
Magnetic bearing control device and control method are disclosed. A magnetic bearing control device according to an embodiment of the present invention comprises: a bearing control unit for outputting a plurality of switch control signals on the basis of gap information of a bearing coil and a rotor and current information applied to the bearing coil; and a coil driving unit for turning a plurality of self-formed switching elements on/off in accordance with the plurality of switch control signals and controlling the amount of current applied to the bearing coil and thus adjusting the magnetic field strength between the bearing coil and the rotor. The bearing control unit generates and outputs the plurality of switch control signals such that bootstrap capacitor charging time of the coil driving unit may be secured. Therefore, a magnetic bearing control circuit structure may be simplified by means of an additional bootstrap capacitor structure.