| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1999: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
In recent years, developments of bearingless drives are undergoing several parts of the world. The bearingless drives are the electric motors or generators with self-magnetic suspensions. Thus, there is increasing expectation of wide range of applications such as vacuum, low or high temperature conditions, harsh environments, long life and highly reliable machines. In fact, extensive developments can be seen in artificial heart blood pumps, canned pumps in chemical plants, semiconductor processes, bio reactors in bio engineering, telescope positioning in space satellites.
In induction motors, used in wide ranges of today's motor drive applications, prototype bearingless motors are built by a Japanese company and Switzerland groups with manufactures and university. The investigators have been done notable research in induction type bearingless motors. A control method to suspend a rotation shaft at rated load torque has been made obvious. However, there exist a possible problem of touch
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down of the shaft during fast change in torque load, high acceleration and decelerations.
In this research, a short time unstable operation of magnetic suspension is seen only at overloaded and transient conditions. During the acceleration tests, two flux signals have been compared. One is search coil flux linkage, which is obtained through integrators connected to search coils. The other is flux reference signal generated by slip-frequency type vector controllers in an induction motor speed feedback loop. It is found that phase angle of these two flux signals are not corresponding in a period of transient conditions. In addition, phase margin of the radial positioning loops is significantly decreased if the phase angle is not corresponding because there exist radial force interference in two-perpendicular axes
To solve the problem, a new orientation method to the air-gap flux is proposed. Successful suspension during high acceleration is found. It is also shown that the optimal field orientation varies in accordance with rotor temperature. Less
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