| Summary: | 碩士 === 國立高雄第一科技大學 === 機械與自動化工程所 === 95 === ABSTRACT
The applications of solid-state inverters for adjustable speed drives are convenient in industrial machine. Many inverters are used to instead of the mechanical gear reducers to control the speed, and created much harmonic current into the electrical power system. The harmonic current resulted the overheating on the electrical devices as motors, transformers, and cables, and also interfered the communication of radio. When the current with harmonic is on the motor, the torque of motor generated by the magnetic fluxes of the rotor shall be the distortion and the vibration. The rotor running should be unstably; sometimes the rotor got a torsional vibration and noises. Now, motors are the most applications as driving devices in the industrial, its stable running and a long-life usefulness will make a good reliability of the plants.
This study on the torsional vibration by the harmonic current from a 6-pulse diodes circuit which is installed on the machine of the plastic plant. To measure the current and the vibration on the motor, we found a phenomenon of torsional vibrations which frequency located at the 6X, 12X of the base frequency. The torsional vibrations created by harmonic current, and the vibration amplitude is almost same as the current rate of basic frequency to the nth order harmonic. If the torsional frequency is the times of the operation speeds, the damages of the relation elements shall be happened. Using a soft coupling to isolate the torsional vibration that delivered to the down stream rotation element is a good selection. Of course, to improve the quality of electrical power system is the best soulution.
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