Dynamic Load Capabilities of Active Electromagnetic Bearings

1991 ◽  
Vol 113 (3) ◽  
pp. 598-603 ◽  
Author(s):  
K. R. Bornstein
Keyword(s):  
Dynamic Load ◽  
Load Capacity ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Saturation Point ◽  
Dynamic Capacity ◽  
Static Capacity ◽  
Wide Range ◽  
Selection Of

Magnetic bearings are finding increasing use in a wide range of applications. It is well known that the static capacity of a bearing can be determined by its saturation point. The static capacity has often been the prime criterion for the selection of magnetic bearing size. The dynamic capacity of a bearing is a much more complicated function. This paper will develop equations to express the dynamic load capacity of a magnetic bearing in terms of its amplifier size, the frequency of excitation, the magnetic airgap, the method of force actuation, and certain nondimensional terms.

Effect of Contact Ratio on Spur Gear Dynamic Load With No Tooth Profile Modifications

1996 ◽  
Vol 118 (3) ◽  
pp. 439-443 ◽  
Author(s):  
Chuen-Huei Liou ◽  
Hsiang Hsi Lin ◽  
F. B. Oswald ◽  
D. P. Townsend
Keyword(s):  
Dynamic Load ◽  
Spur Gear ◽  
Tooth Size ◽  
Contact Ratio ◽  
Gear Dynamics ◽  
Wide Range ◽  
Gear Contact ◽  
Center Distance ◽  
Selection Of ◽  
Better Than

This paper presents a computer simulation showing how the gear contact ratio affects the dynamic load on a spur gear transmission. The contact ratio can be affected by the tooth addendum, the pressure angle, the tooth size (diametral pitch), and the center distance. The analysis presented in this paper was performed by using the NASA gear dynamics code DANST. In the analysis, the contact ratio was varied over the range 1.20 to 2.40 by changing the length of the tooth addendum. In order to simplify the analysis, other parameters related to contact ratio were held constant. The contact ratio was found to have a significant influence on gear dynamics. Over a wide range of operating speeds, a contact ratio close to 2.0 minimized dynamic load. For low-contact-ratio gears (contact ratio less than two), increasing the contact ratio reduced gear dynamic load. For high-contact-ratio gears (contact ratio equal to or greater than 2.0), the selection of contact ratio should take into consideration the intended operating speeds. In general, high-contact-ratio gears minimized dynamic load better than low-contact-ratio gears.

scholarly journals Development and Experimental Validation of Auxiliary Rolling Bearing Models for Active Magnetic Bearings (AMBs) Applications

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Anna Tangredi ◽  
Enrico Meli ◽  
Andrea Rindi ◽  
Alessandro Ridolfi ◽  
Pierluca D’Adamio ◽  
...  
Keyword(s):  
Load Capacity ◽  
Critical Phenomenon ◽  
Magnetic Bearing ◽  
Design Tool ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
Active Magnetic Bearings ◽  
Short Period ◽  
Auxiliary Bearing ◽  
Bearing System

Nowadays, the search for increasing performances in turbomachinery applications has led to a growing utilization of active magnetic bearings (AMBs), which can bring a series of advantages thanks to their features: AMBs allow the machine components to reach higher peripheral speeds; in fact there are no wear and lubrication problems as the contact between bearing surfaces is absent. Furthermore, AMBs characteristic parameters can be controlled via software, optimizing machine dynamics performances. However, active magnetic bearings present some peculiarities, as they have lower load capacity than the most commonly used rolling and hydrodynamic bearings, and they need an energy source; for these reasons, in case of AMBs overload or breakdown, an auxiliary bearing system is required to support the rotor during such landing events. During the turbomachine design process, it is fundamental to appropriately choose the auxiliary bearing type and characteristics, because such components have to resist to the rotor impact; so, a supporting design tool based on accurate and efficient models of auxiliary bearings is very useful for the design integration of the Active Magnetic Bearing System into the machine. This paper presents an innovative model to accurately describe the mechanical behavior of a complete rotor-dynamic system composed of a rotor equipped with two auxiliary rolling bearings. The model, developed and experimentally validated in collaboration with Baker Hughes a GE company (providing the test case and the experimental data), is able to reproduce the key physical phenomena experimentally observed; in particular, the most critical phenomenon noted during repeated experimental combined landing tests is the rotor forward whirl, which occurs in case of high friction conditions and greatly influences the whole system behavior. In order to carefully study some special phenomena like rotor coast down on landing bearings (which requires long period of time to evolve and involves many bodies and degrees of freedom) or other particular events like impacts (which occur in a short period of time), a compromise between accuracy of the results and numerical efficiency has been pursued. Some of the elements of the proposed model have been previously introduced in literature; however the present work proposes some new features of interest. For example, the lateral and the axial models have been properly coupled in order to correctly reproduce the effects observed during the experimental tests and a very important system element, the landing bearing compliant suspension, has been properly modelled to more accurately describe its elastic and damping effects on the system. Furthermore, the model is also useful to characterize the frequencies related to the rotor forward whirl motion.

Hybrid (hydrodynamic + permanent magnetic) journal bearings

2007 ◽  
Vol 221 (8) ◽  
pp. 881-891 ◽  
Author(s):  
H Hirani ◽  
P Samanta
Keyword(s):  
Permanent Magnets ◽  
Load Capacity ◽  
Rapid Development ◽  
Experimental Studies ◽  
Radial Force ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Axial Thrust ◽  
Hydrodynamic Bearing ◽  
Load Carrying

Survey of patents on bearings indicates the maturity of hydrodynamic and rapid development of magnetic bearings. Active magnetic bearings are costlier compared with permanent magnetic bearings. To understand the performance characteristics of permanent magnetic bearings, an experimental setup has been developed. Experimental studies on radial permanent magnetic bearings demonstrated the drawbacks, such as high axial thrust and low load capacity. This has led the authors to hybridize the permanent magnet with hydrodynamic technology and to explore the possibility of achieving the low starting torque of a permanent magnetic bearing and the medium to high load carrying capacity of a hydrodynamic bearing in a single bearing arrangement. Simulation is carried out in order to reduce axial force-effect and enhance the radial force supported by the permanent magnetic bearing. Results of simulation on permanent magnetic bearing have been compared with that of published research papers. Finally an algorithm has been developed to investigate the coupling of forces generated by permanent magnets and hydrodynamic actions. Results of load sharing have been reported. The experimentally measured displacements of the shaft running at 500, 2000, and 3000 r/min have been plotted. The effect of hydrodynamics on shaft orbit has been illustrated.

Dynamic Analysis and Control of High Speed and High Precision Active Magnetic Bearings

1992 ◽  
Vol 114 (4) ◽  
pp. 623-633 ◽  
Author(s):  
K. Youcef-Toumi ◽  
S. Reddy
Keyword(s):  
Time Delay ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Successful Operation ◽  
Highly Nonlinear ◽  
Wide Range ◽  
And Control ◽  
Digital Time

The successful operation of actively controlled magnetic bearings depends greatly on the electromechanical design and control system design. The function of the controller is to maintain bearing performance in the face of system dynamic variations and unpredictable disturbances. The plant considered here is the rotor and magnetic bearing assembly of a test apparatus. The plant dynamics consisting of actuator dynamics, rigid rotor dynamics and flexibility effects are described. Various components of the system are identified and their corresponding linearized theoretical models are validated experimentally. Tests are also run to identify the coupling effects and flexibility modes. The highly nonlinear behavior of the magnetic bearings in addition to the inherent instability of such a system makes the controller design complex. A digital Time Delay Controller is designed and its effectiveness evaluated using several simulations based on linear and nonlinear models for the bearing including bending mode effects. This controller is implemented as an alternative to an existing linear analog compensator. Several experiments are conducted with each controller for spinning and nonspinning conditions. These include time responses, closed loop frequency responses and disturbance rejection responses. The experimental results and comparisons between those of a digital Time Delay Controller and an analog compensator indicate that the Time Delay Controller has impressive static and dynamic stiffness characteristics for the prototype considered. The Time Delay Controller also maintains almost the same dynamic behavior over a significantly wide range of rotor speeds.

scholarly journals Effect of Contact Ratio on Spur Gear Dynamic Load

1992 ◽  
Author(s):  
Chuen-Huei Liou ◽  
Hsiang Hsi Lin ◽  
Fred B. Oswald ◽  
Dennis P. Townsend
Keyword(s):  
Dynamic Load ◽  
Spur Gear ◽  
Tooth Size ◽  
Contact Ratio ◽  
Gear Dynamics ◽  
Wide Range ◽  
Gear Contact ◽  
Center Distance ◽  
Selection Of ◽  
Better Than

Abstract This paper presents a computer simulation showing how the gear contact ratio affects the dynamic load on a spur gear transmission. The contact ratio can be affected by the tooth addendum, the pressure angle, the tooth size (diametral pitch), and the center distance. The analysis presented in this paper was performed by using the NASA gear dynamics code DANST. In the analysis the contact ratio was varied over the range 1.20 to 2.40 by changing the length of the tooth addendum. In order to simplify the analysis, other parameters related to contact ratio were held constant. The contact ratio was found to have a significant influence on gear dynamics. Over a wide range of operating speeds a contact ratio close to 2.0 minimized dynamic load. For low-contact-ratio gears (contact ratio less than 2.0), increasing the contact ratio reduced the gear dynamic load. For high-contact-ratio gears (contact ratio equal to or greater than 2.0), the selection of contact ratio should take into consideration the intended operating speeds. In general, high-contact-ratio gears minimized dynamic load better than low-contact-ratio gears.

Optimized Realization of Fault-Tolerant Heteropolar Magnetic Bearings for Active Vibration Control

1999 ◽  
Author(s):  
Uhn Joo Na ◽  
Alan Palazzolo
Keyword(s):  
Lagrange Multiplier ◽  
Global Minimum ◽  
Fault Tolerant ◽  
Load Capacity ◽  
Active Vibration Control ◽  
Fault Tolerant Control ◽  
Optimization Method ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Control Voltage

Abstract The nature of coupling in the heteropolar magnetic bearings permits other remaining active coils in the stator to assume actions of the failed coils to produce the same force resultants. This fault-tolerant control usually reduces load capacity because the redistribution of the magnetic flux which compensates for the failed coils leads to premature saturation in the stator or journal. Distribution matrix of voltages which consists of redefined biasing voltage vector and two control voltage vectors can be optimized in the manner that peak flux density is minimized. An elegant optimization method using Lagrange Multiplier is presented in this paper. The redistribution matrices calculated with Lagrange Multiplier method were compared with Maslen and Meeker’s solutions, local minima are guaranteed and also the global minimum can be obtained if an effective global minimum searching algorithm is used. The linearized control forces can be realized up to certain combination of 5 poles failed for the 8 pole magnetic bearing. Position stiffness and voltage stiffness are calculated for the fault-tolerant magnetic bearings. Simulations show that fault-tolerant control of the multiple poles failed magnetic bearings with a horizontal flexible rotor can be stabilized with reduced load capacity.

Steady-State Control of Hybrid Foil-Magnetic Bearings

2012 ◽  
Author(s):  
Ye Tian ◽  
Yanhua Sun ◽  
Lie Yu
Keyword(s):  
Steady State ◽  
Load Capacity ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
State Control ◽  
Foil Bearings ◽  
Foil Bearing ◽  
State Controller ◽  
Steady State Control ◽  
And Control

A hybrid foil-magnetic bearing is combination of a foil bearing and a magnetic bearing, which takes advantages of both bearings while compensating each other the weaknesses. It is a solution of friction and wear of foil bearings at low speeds and limited load capacity of magnetic bearings. Furthermore, load sharing and control of dynamics can be achieved in a hybrid foil-magnetic bearing. However, in the hybrid foil-magnetic bearing, the journal should run at certain eccentricity and attitude angle in order to take part of the loads, but the magnetic bearing would attempt to force the journal to the reference position at all times while using a conventional PID controller. Therefore, it is necessary to design a new control algorithm to overcome the contradictions. In this paper, the steady-state characteristics of a hybrid foil-magnetic bearing were analyzed. Then a searching algorithm was presented and a steady-state controller was designed to determine the steady-state working position of the hybrid foil-magnetic bearings. Finally, simulations were done to verify performances of the searching algorithm and designed steady-state controller, and the results show its validity.

Multi-Objective Optimization Design of Nonlinear Magnetic Bearing Rotordynamic System

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Wan Zhong ◽  
Alan Palazzolo ◽  
Xiao Kang
Keyword(s):  
Power Loss ◽  
Optimization Design ◽  
Hot Spot ◽  
Load Capacity ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Control Law ◽  
Steady State Operation ◽  
Mass Minimization ◽  
Compact Design

Nonlinear vibrations and their control are critical in improving the magnetic bearings system performance and in the more widely spread use of magnetic bearings system. Multiple objective genetic algorithms (MOGAs) simultaneously optimize a vibration control law and geometrical features of a set of nonlinear magnetic bearings supporting a generic flexible, spinning shaft. The objectives include minimization of the actuator mass, minimization of the power loss, and maximization of the external static load capacity of the rotor. Levitation of the spinning rotor and the nonlinear vibration amplitude by rotor unbalance are constraint conditions according to International Organization for Standardization (ISO) specified standards for the control law search. The finite element method (FEM) was applied to determine the temperature distribution and identify the hot spot of the actuator during steady-state operation. Nonlinearities include magnetic flux saturation, and current and voltage limits of power amplifiers. Pareto frontiers were applied to identify and visualize the best-compromised solutions, which give a most compact design with minimum power loss whose vibration amplitudes satisfy ISO standards.

Magnetic Bearing Design for Reduced Power Consumption

1996 ◽  
Vol 118 (4) ◽  
pp. 839-846 ◽  
Author(s):  
E. H. Maslen ◽  
P. E. Allaire ◽  
M. D. Noh ◽  
C. K. Sortore
Keyword(s):  
Power Consumption ◽  
Permanent Magnet ◽  
Gas Turbines ◽  
Load Capacity ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Fluid Film ◽  
Total Power ◽  
Total Power Consumption ◽  
Bearing Design

Magnetic bearings have relatively low power consumption compared to fluid film and rolling element bearings. They are now candidates for supporting gas turbines and aeropropulsion engines. This paper describes the design and construction of permanent magnet biased, actively controlled magnetic bearings for a flexible rotor. The rotor was originally supported in fluid film bearings consuming as much as 3000 watts of power. For the magnetic bearing, both permanent magnets and electromagnets are used in a configuration which effectively provides the necessary fluxes in the appropriate air gaps to support the rotor. The theoretical development related to the bearing design is presented along with some experimental performance results. The results include measurements of power consumption, load capacity, bearing linearized coefficients, and the dynamic response of the rotor. The measured total power consumption, excluding shaft losses, was 210 watts in the permanent magnet biased bearing.

Passive Contra-Magnetized Parallel-Airgap Serial Flux Magnetic Bearings

2010 ◽  
Vol 224 (11) ◽  
pp. 2515-2524
Author(s):  
K Kalita ◽  
W K S Khoo ◽  
S D Garvey ◽  
R J Hill-Cottingham ◽  
D Rodger ◽  
...  
Keyword(s):  
Load Capacity ◽  
Three Dimensional ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Two Dimensional ◽  
Specific Load ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Automatic Mesh

Conventional magnetic bearings accomplish a specific load capacity, defined as the ratio of maximum sustainable weight to the total self-weight, of up to 35:1. In this paper, the authors introduce a class of passive magnetic bearings that comprise a large number of parallel airgaps and discs and can deliver specific load capacities substantially higher than 35:1. Two-dimensional planar, two-dimensional axi-symmetric, and three-dimensional finite-element analysis (FEA) have been undertaken to predict the force capability of the bearings. An unoptimized prototype passive magnetic bearing is constructed to demonstrate the concept and its force-carrying capacity. The experimental results are then compared with those obtained from the FEA. Further optimization of the bearings is done across the whole design space comprising tens of thousands of models using an automatic mesh generator in conjunction with solving the FE models in nested loops.

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