A novel approach for design optimisation of radial active magnetic bearing

Journal Bearings are excellent bearings due to their large load carrying capacity and favorable damping characteristics. However, Journal bearings are known to be prone to instabilities. The oil whirl and oil whip instabilities limit the rotor maximum rotating speed. In this paper, a novel approach is used to control the Journal bearing (JB) instability. An Active Magnetic Bearing (AMB) is used to overcome the JB instability and to increase its range of operation. The concept is quite simple: rather than using the AMB as a load carrying element, the AMB is used as a controller only, resulting in a much smaller and more efficient AMB. The load carrying is done by the Journal bearings, exploiting their excellent load carrying capabilities, and the JB instability is overcome with the AMB. This results in a combined AMB/JB that exploits the advantages of each device, and eliminates the deficiencies of each bearing. Different controllers for the AMB to control the JB instability are examined and compared theoretically and numerically. The possibility of collocating the JB and the AMB is also examined. The results illustrate the effectiveness of the concept.

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An Improved Catcher Bearing Model and an Explanation of the Forward Whirl/Whip Phenomenon Observed in Active Magnetic Bearing Transient Drop Experiments

Volume 7B: Structures and Dynamics ◽

10.1115/gt2013-94594 ◽

2013 ◽

Cited By ~ 4

Author(s):

Jason Wilkes ◽

Giuseppe Vannini ◽

Jeff Moore ◽

David Ransom

Keyword(s):

High Speed ◽

Experimental Tests ◽

Magnetic Bearing ◽

Active Magnetic Bearing ◽

Constant Frequency ◽

Axial Thrust ◽

Novel Approach ◽

Transient Simulations ◽

The Coefficient Of Friction ◽

Reaction Forces

Though many approaches have been proposed in the literature to model the reaction forces in a catcher bearing (CB), there are still phenomena observed in experimental tests that cannot be explained by existing models. The following paper presents a novel approach to model a CB system. Some of the elements in the model have been previously introduced in the literature; however, there are other elements in the proposed model that are new, providing an explanation for the forward whirling phenomena that has been observed repeatedly in the literature. The proposed CB model is implemented in a finite element rotordynamic package, and nonlinear time-transient simulations are performed to predict published experimental results of a high speed vertical sub-scale compressor; with no other forces present in the model, the agreement between simulations and experimental data is favorable. The results presented herein show that friction between the journal and axial face of the catcher bearing results in a forward cross-coupled force that pushes the rotor in the direction of rotation. This force is proportional to the coefficient of friction between the axial face of the rotor and catcher bearing and the axial thrust on the rotor. This force results in synchronous whirl when the running speed is below a combined natural frequency of the rotor-stator system, and constant frequency whip when the speed is above a whip frequency.

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An Improved Catcher Bearing Model and an Explanation of the Forward Whirl/Whip Phenomenon Observed in Active Magnetic Bearing Transient Drop Experiments

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4025890 ◽

2013 ◽

Vol 136 (4) ◽

Cited By ~ 9

Author(s):

Jason Wilkes ◽

Jeff Moore ◽

David Ransom ◽

Giuseppe Vannini

Keyword(s):

High Speed ◽

Experimental Tests ◽

Magnetic Bearing ◽

Active Magnetic Bearing ◽

Constant Frequency ◽

Axial Thrust ◽

Novel Approach ◽

Transient Simulations ◽

The Coefficient Of Friction ◽

Reaction Forces

Though many approaches have been proposed in the literature to model the reaction forces in a catcher bearing (CB), there are still phenomena observed in experimental tests that cannot be explained by existing models. The following paper presents a novel approach to model a CB system. Some of the elements in the model have been previously introduced in the literature; however, there are other elements in the proposed model that are new, providing an explanation for the forward whirling phenomena that has been observed repeatedly in the literature. The proposed CB model is implemented in a finite-element rotordynamic package, and nonlinear time-transient simulations are performed to predict published experimental results of a high-speed vertical subscale compressor; with no other forces present in the model, the agreement between simulations and experimental data is favorable. The results presented herein show that friction between the journal and axial face of the catcher bearing results in a forward cross-coupled force that pushes the rotor in the direction of rotation. This force is proportional to the coefficient of friction between the axial face of the rotor and catcher bearing and the axial thrust on the rotor. This force results in synchronous whirl when the running speed is below a combined natural frequency of the rotor-stator system and constant frequency whip when the speed is above a whip frequency.

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Modelling and Simulation of Nonlinear Jump Phenomena of a Non-ideal Rotor Involving Fractional Order PD Controller

Journal of Physics Conference Series ◽

10.1088/1742-6596/2115/1/012029 ◽

2021 ◽

Vol 2115 (1) ◽

pp. 012029

Author(s):

Gaurav Ghosh ◽

Abhishek Kumar Jha ◽

Sovan Sundar Dasgupta

Keyword(s):

High Speed ◽

Transient Analysis ◽

Input Power ◽

Magnetic Bearing ◽

Active Magnetic Bearing ◽

Pd Controller ◽

Sommerfeld Effect ◽

Locus Method ◽

Novel Approach ◽

Jump Phenomena

Abstract Rotating machinery with high speed powered by industrial motors frequently suffers from instability by exhibiting non-linear jump phenomena, formally known as Sommerfeld effect. The drives whose excitation is a function of the system responses, referred to as non-ideal. The system dynamics of such systems exhibit a couple of complex and interesting features when the input power exceeds a critical value. The present research suggests a novel approach to study the efficacy of active magnetic bearing with fractional PD controller to suppress the instability caused by the Sommerfeld effect. The steady-state results obtained by solving the system characteristic equation numerically is compared with the transient analysis. Finally, root locus method is introduced to obtain the bifurcation points at which this kind of instability completely disappears.

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Controlling Journal Bearing Instability Using Active Magnetic Bearings

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3078785 ◽

2009 ◽

Vol 132 (1) ◽

Cited By ~ 31

Author(s):

A. El-Shafei ◽

A. S. Dimitri

Keyword(s):

Journal Bearing ◽

Magnetic Bearing ◽

Journal Bearings ◽

Active Magnetic Bearing ◽

Rotating Speed ◽

Damping Characteristics ◽

Oil Whip ◽

Novel Approach ◽

Oil Whirl ◽

Load Carrying

Journal bearings (JBs) are excellent bearings due to their large load carrying capacity and favorable damping characteristics. However, journal bearings are known to be prone to instabilities. The oil whirl and oil whip instabilities limit the rotor maximum rotating speed. In this paper, a novel approach is used to control the journal bearing instability. An active magnetic bearing (AMB) is used to overcome the JB instability and to increase its range of operation. The concept is quite simple: Rather than using the AMB as a load carrying element, the AMB is used as a controller only, resulting in a much smaller and more efficient AMB. The load carrying is done by the journal bearings, exploiting their excellent load carrying capabilities, and the JB instability is overcome with the AMB. This results in a combined AMB/JB that exploits the advantages of each device and eliminates the deficiencies of each bearing. Different controllers for the AMB to control the JB instability are examined and compared theoretically and numerically. The possibility of collocating the JB and the AMB is also examined. The results illustrate the effectiveness of the concept.

Download Full-text