Mochimitsu Komori

New Concept for Flywheel Energy Storage System Using SMB and PMB

Since a few years ago, electrical energy storage has been attractive as an effective use of electricity and coping with the momentary voltage drop. Above all, flywheel energy storage systems using superconductor have advantages of long life, high energy density, and high efficiency. Our experimental machine uses a superconducting magnetic bearing (SMB) together with a permanent magnet bearing (PMB) and plans to reduce the overall cost and cooling cost. Flywheel energy storage systems operate by storing energy mechanically in a rotating flywheel. The generating motor is used to rotate the flywheel and to generate electricity from flywheel rotation. The generating motor consists of a 2-phase 4-pole brushless DC motor and a Hall sensor. A purpose of this study is the development of a compact flywheel energy storage system using SMB and PMB with new concept. This paper shows the new model of flywheel by using the concept of yajirobei (balancing toy) that the center of gravity of mass is lower than supporting point. By using this concept, the flywheel has higher storage energy compared with conventional ones. Furthermore, we also purpose to improve and evaluate motor drive (DC motor) to increase the rotational speed, and estimate the system at momentary voltage drop.

A hybrid-type superconducting magnetic bearing system with nonlinear control

In this paper, a hybrid-type superconducting magnetic bearing (SMB) system with nonlinear control is discussed. The hybrid-type SMB system consists of passive-type SMBs, active-type magnetic bearings (AMBs), a rotor, and sensors. The rotor position is controlled by nonlinear controller with no-bias currents. Because the controller does not need bias currents applied to the electromagnets, the energy losses are considered to be less than other magnetic bearing systems. The displacements of the rotor are suppressed by both the SMBs and the AMBs. The superconductors of the SMBs were field-cooled. Compliance for the bearings, displacements of the rotating rotor, and energy losses for the system were investigated. The results show that the hybrid-type SMB system with nonlinear control has good performances in these evaluations.

Flywheel Energy Storage System Using SMB and PMB

A new energy storage flywheel system using a superconducting magnetic bearing (SMB) and a permanent magnet bearing (PMB) is proposed. The superconducting magnetic bearing (SMB) suppresses the vibrations of the flywheel rotor. The permanent magnet bearing (PMB) passively controls the rotor position. The energy storage flywheel system is characterized by using the two different type magnetic bearings of permanent magnet bearing (PMB) and superconducting magnetic bearing (SMB). Dynamics of the new energy storage flywheel system are discussed in this paper.

A magnetically driven linear microactuator with new driving method

Electromagnetically driven microactuators are of interest because they have the potential to generate large deflections. Thus, we have been studying magnetically driven microactuators. This time, a magnetically driven linear microactuator has been newly developed by using microfabrication techniques. The microactuator is composed of a mobile microplatform (mover) with some permanent magnets (PMs) and a stator with a large number of planar coils. In this paper, two types of microplatforms are fabricated and compared with each other. Furthermore, static and dynamic characteristics of the magnetically driven linear microactuator are discussed.

Improvement of Energy Storage Flywheel System With SMB and PMB and Its Performances

Our group has developed a new energy storage flywheel system using a superconducting magnetic bearing (SMB) and a permanent magnet bearing (PMB). The superconducting magnetic bearing (SMB) suppresses the vibrations of the flywheel rotor. The permanent magnet bearing (PMB) passively controls the rotor position. The energy storage flywheel system is characterized by using the two different type magnetic bearings of PMB and SMB. Dynamics and charge-discharge characteristics are improved and discussed in this paper.

A levitated motor with superconducting magnetic bearings assisted by self-sensing AMBs

This paper describes newly developed superconducting magnetic bearings (SMBs) assisted by self-sensing active magnetic bearings (AMBs). The self-sensing AMBs detect the gaps between rotor and electromagnets. The principle of the self-sensing sensors is based on a differential transformer. The sensitivity in liquid nitrogen is almost equal to that in air. The sensor is found to be useful in liquid nitrogen at 77 K (-196 /spl deg/C). Moreover, the sensors are applied to the SMBs. Dynamics of the SMBs with self-sensing AMBs are discussed. From the results, it is found that the system is useful and promising.

Dynamic characteristics of a high‐Tc superconducting bearing with a set of alternating‐polarity magnets

Dynamics of a superconducting bearing with a high‐Tc superconductor and a set of alternating‐polarity magnets are discussed. The superconductor used is prepared by the quench and melt growth process. The set of magnets levitates over the superconductor which is field cooled in liquid nitrogen. To construct a dynamic model of the superconducting bearing, responses for impulse forces given to the levitating magnets in vertical direction are investigated. Damped free‐vibration curves of the levitating magnets are observed. Dynamic stiffness and viscous damping coefficient can be defined by using the periodical vibration curves. It is also found that the stiffness and the damping coefficient depend on the width of a bar magnet. The resultant energy loss of the superconducting bearing is evaluated by using the force‐displacement relationship and Bean’s critical state model [Phys. Rev. Lett. 8, 250 (1962)].

STATIC LEVITATION IN A HIGH-TC SUPERCONDUCTOR TILE ON MAGNET ARRANGEMENTS

Static characteristics of a levitational mechanism are studied. The levitational mechanism consists of a high‐Tc superconductor tile (type‐II superconductor) and a magnet arrangement of the same size bar magnets with alternating magnetic pole pattern. The levitation pressures have hysteresis loops because of the flux pinning effect. By using the alternating pole pattern of magnets larger static levitation pressure in proportion to the arrangement can be obtained over a wide area. Moreover the levitation pressure can be optimized with respect to the width of a bar magnet of the alternating pole pattern.

Basic study of a magnetically levitated conveyer using superconducting magnetic levitation

This paper discusses a newly developed conveyer that uses superconducting levitation. The conveyer is composed of a levitated stage with a permanent magnet (PM) and a superconductor with an electromagnet and a Hall sensor. The gap between the PM stage and the superconductor is detected by using the Hall sensor and the current of the electromagnet coil. In order to suppress vibrations of the PM stage, PD (proportional & differential) control using adoptive control method is applied to the system. Control forces are produced by the electromagnet under the superconductor. The dynamics of the levitated stage are discussed in the case that PD control and only D (differential) control are applied to the system.

A prototype of flywheel energy storage system suppressed by hybrid magnetic bearings with H/sup /spl infin// controller

This paper discusses a prototype of miniature flywheel energy storage system. The system consists of a rotor with a flywheel disk and a pair of hybrid magnetic bearings (HMBs). The HMB is composed of both superconducting magnetic bearings (SMBs) and active magnetic bearings (AMBs). An H-infinity control method and zero bias method are applied to the AMB. In this paper, the design and dynamics of the flywheel energy storage system are discussed.