Site:           Mitsubishi Electric Corporation (MELCO)
                Advanced Technology R&D Center
                8-1-1, Tsukaguchi-Honmachi
                Amagasaki City, Hyogo 661, Japan
                http://www.melco.co.jp:80/index_e.htm
Date Visited:   6 June 1996
WTEC Attendees: R. Schwall (report author), 
                R.D. Blaugher, 
                J. Daley, 
                G. Gamota, 
                P. Grant, 
                H. Morishita, 
                R. Sokolowski
Hosts:          Dr. Ken Sato, General Manager, 
                   Electromechanical Technology Lab
                Shiro Nakamura, Deputy Manager, 
                   Electromechanical Systems Department
                Hisao Watarai, Manager, 
                   Metal and Ceramics Technology Department
                Dr. Mitsunobu Wakata, Manager, 
                   Superconducting Materials Group
                Dr. Hideto Yoshimura, Manager, 
                   Cryogenics and Superconductivity Group
                Dr. Kazuyoshi Kojima, Strategic R&D Planning Group

BACKGROUND

The history of the MELCO effort in superconductivity can be traced back to the early 1960s when work began worldwide on high field Type II superconductors. MELCO currently maintains an active program in many areas of superconductivity. Figure MELCO.1 shows distribution of personnel by project area.

The WTEC team's visit was to the Advanced Technology R&D Center, which has approximately 600 researchers and 150 support personnel. Figure MELCO.2 gives the center's top-level organization.

The superconductivity effort is divided between three laboratories. Coil research is in the Electromechanical Technology Laboratory, conductors research is in the Metals and Ceramics Technology Department of the Materials Technology Lab (which is physically located at the Sagami Administration Center), and electronic devices are pursued in the Advanced Devices Technology Lab.

SUPERCONDUCTING MATERIALS

Nb3Sn for ITER-CS Model Coil

The CS model coil for the International Thermonuclear Experimental Reactor (ITER) is a 13 T pulsed magnet and requires Nb₃Sn strands with high J_c and low hysteresis loss. MELCO uses an internal tin process and has successfully manufactured 600 km (2.75 tons) of strands. At the present time Nb₃Sn conductor is not a production business for MELCO, and the conductor group is exploring high field NMR and refrigerated magnets as markets for the conductor technology. Continuing research focuses on increasing J_c and decreasing cost.

HTS Materials

MELCO has halted the development and production of long lengths of HTS conductor and has focused resources on the search for a strong pinning system without weak links and on processing for the Bi system. Issues mentioned relative to the Bi system were process development to increase filament density and improve preferential orientation of individual crystals.

Research continues on HTS current leads, and MELCO researchers have produced (Bi, Pb)-2223 current leads with J_c(77 K, 0T) of about 10 A/mm²; the target at the time of the WTEC visit was 100 A/mm² with high mechanical strength.

Fig. MELCO.1. Percentage of R&D manpower resources.

Fig. MELCO.2. Advanced Technology R&D Center.

EQUIPMENT

Generators

MELCO has been working on superconducting generators since 1971. It participated in a Ministry of International Trade and Industry (MITI) 6 MW program from 1974 to 1976, and a MITI 30 MW program from 1977 to 1982, and is currently participating in the Super-GM program, which has a duration of 10 years. The WTEC team's hosts stated that the only realistic application of the present 70 MW system would be stabilization of the power grid. Given the very competitive nature of the worldwide generator business, MELCO management will find it very difficult to economically justify generator R&D with internal funding after completion of the government program.

Transformers

The panel's hosts at MELCO indicated that they feel the projected costs for HTS transformers are too high to be commercially successful. If the prices can be made competitive, their opinion is that reduced weight is the largest advantage for the Japanese market.

SMES

MELCO is participating in a program with KEPCO targeting 400 kJ Nb₃Sn coils. Three coils made by three different companies have been installed and tested this year.

Flywheels

MELCO has completed a 100 W-hr system as part of a Shikoku Electric Power Company (SEPCO) program. The flywheel is alloy steel in a stainless jacket. The bearing features a rotating magnet and a stationary YBCO element operating in liquid nitrogen. MELCO is also participating in a MITI/NEDO study on flywheels that is reported and covered in more detail in the NEDO and ISTEC reports.

MRI Magnets

MELCO produces magnets for MRI systems marketed by Shimadzu. It currently produces a magnet with zero helium consumption, and it has about 50 of these in the field. The refrigerator is a three-stage Gifford McMahon (GM) with a Ho_1.5Er_1.5Ru regenerator developed by Mitsubishi Materials.

Cryogen-Free Magnets

MELCO is active in this area and has completed a Klystron magnet that operates at 3.8 K with a GM refrigerator. Its largest low-temperature GM machine produces 2.2 W at 4.2 K.

Synchrotron Ring

MELCO has produced a synchrotron ring for industrial research such as X-ray lithography and is currently using it for development of the 1 Gbit memory chip. It would produce such rings if a commercial market developed.

MAGLEV Refrigerators

At the time of the WTEC visit, the heat load on MELCO's MAGLEV magnets was 5 W static and 3 W due to induced currents during operation.