China
Africa
Explore chapters and articles related to this topic
Standby Power Systems
Published in Michael F. Hordeski, Emergency and Backup Power Sources:, 2020
Low-speed flywheels are usually made from steel while highspeed flywheels are usually made from carbon or carbon and fiberglass composites that will withstand the higher stresses associated with higher rpm. Higher rpm also creates greater problems with friction losses from bearings and air drag. High-speed flywheels typically use magnetic bearings and vacuum enclosures to reduce or eliminate these sources of friction. Magnetic bearings allow the flywheel to levitate, fundamentally eliminating frictional losses associated with conventional bearings. Some low-speed flywheel use only conventional mechanical bearings but most flywheels use a combination of the two bearing types. Vacuums are also used in some low-speed flywheels.
Rotor–Stator Interaction
Published in Arthur W. Lees, Vibration Problems in Machines, 2020
While the bearings described in the previous two subsections predominate, there are other types in operation. Of these, perhaps the most important are magnetic bearings, of which there are two main types: passive and active. In both cases, the big advantage is that by using a magnetic field to levitate and locate the rotor, all contact with the rotor is avoided and frictional losses are extremely low. In the passive type, permanent magnets are used to impose a fixed field on the rotor.
Introduction
Published in Q. Jane Wang, Dong Zhu, Interfacial Mechanics, 2019
A magnetic bearing utilizes magnetic suspension as the load-supporting medium to avoid direct surface contact. The magnetic field allows relative motion in the bearing components under an extremely low friction and theoretically zero mechanical wear. Permanent magnets and electromagnets are both feasible for magnetic bearing design. However, the latter provides a convenience of better performance control. Magnetically levitated (MAGLEV) train is currently being commercialized that has great potential especially for the future high-speed transportation, using magnets to replace the conventional wheels, axles, bearings, and rails, as shown in Figure 1.12. The magnetic levitation lifts the vehicle from the guide ways with a small clearance and permits extremely smooth high-speed motion.
Optimal Adaptive Magnetic Suspension Control of Rotary Impeller for Artificial Heart Pump
Published in Cybernetics and Systems, 2022
Amjad J. Humaidi, Saleem Khalefa Kadhim, Ahmed Sharhan Gataa
On the other hand, an active magnetic bearing (AMB) technology is used in the design of HeartMate II pump. This technology employs two AMB systems to keep the rotating shaft (impeller) suspended or hanged (Hoshi, Shinshi, and Takatani 2006). In the ABM technology, the classical problem of rotor bearing has been solved by magnetically hanging the rotor without any connection. When compared with traditional bearing technology, magnetic bearing technology has two main advantages: lack of wear and tear and mechanical friction, which lead to less rise in temperature and longer pump life. For such reasons, many industrial applications have applied this technology; in particular the application of blood pumps for rotor suspension (Yang et al. 2016). The use of magnetic suspension technology in AH pumps reduces the bearing friction and hence to minimize the blood damage. In addition, this AMB technology enhances the reliability and functionality of AHV device and it is necessary for its service life and hence this technique could decrease the occurrence of cardiac surgery.
Thermoelastic analysis and multi-objective optimal design of functionally graded flywheels for energy storage systems
Published in Engineering Optimization, 2020
Alper Uyar, Aytac Arikoglu, Guven Komurgoz, Ibrahim Ozkol
Because of the rapid mechanization and technological innovations that have taken place since the Industrial Revolution, energy requirements have been increasing at an unprecedented rate. The limited availability of known energy resources makes it necessary to find solutions that enable more efficient use of energy. In this context, flywheel energy storage systems (FESSs) have found widespread application in areas such as electrical networks, uninterruptible power supplies, vehicle traction, space and military applications, grid stability and voltage sag control of electrical networks owing to their strengths of high energy capacity, fast response, long life, low maintenance and environmentally friendly characteristics. FESSs are typically classified into two types depending on the speed of the application, i.e. systems with rotation speeds up to 10,000 rpm are accepted as low-speed applications whereas those with speeds above 10,000 rpm are accepted as high-speed applications. Conventional mechanical bearings can be used in low-speed applications. However, they become unsuitable as a result of friction losses and life-cycle concerns in high-speed applications. Therefore, in high-speed applications, such as speeds up to 100,000 rpm, magnetic bearings are needed to support the rotational loads.
Design and Analysis of Embedded I&C for a Fully Submerged Magnetically Suspended Impeller Pump
Published in Nuclear Technology, 2018
Alexander M. Melin, Roger A. Kisner
Most magnetic bearing research focuses on new geometric configurations and control theory. The most common magnetic bearing control design method is to linearize the system about the operating point and create independent proportional-integral-derivative controllers for each axis.13,14 This decoupled control design assumes that the shaft is rigid and well balanced and that gyroscopic and other external shaft forces are minimal. For many operational environments these assumptions are valid. For example, vacuum turbopumps have minimal aerodynamic forces on the shaft and very precisely balanced shafts because they operate at high rotational speeds. Much of the research into control design for magnetic bearings has focused on relaxing these assumptions. In Refs. 16 and 17, fuzzy-logic–based controllers for magnetic bearings are developed. Other nonlinear controllers developed for magnetic bearings use sliding-mode control.18,19 Robust controllers are typically used in magnetic bearings to compensate for vibrations due to shaft imbalances and flexible mode shapes. In Ref. 20, a robust controller is developed based on eigenstructure assignment. An robust controller for shaft imbalance compensation was developed in Ref. 21. An adaptive controller was developed in Ref. 22 to perform shaft auto-centering with an unknown mass imbalance on the rotor.