근래에 전기추진선박의 필요성이 대두되고 있으며 특수선박을 시작으로 건조가 증가되고 있는 실정이다. 하지만 선박은 운항 환경에 따라 추진기의 출력 토크 및 속도의 변동이 심하므로 전기추진시스템에 큰 영향을 미친다. 대표적으로 출 입항시, 정상상태의 대양 항해시, 황천 항해시에 선박 추진시스템의 토크 및 속도 변동이 짧지만 빈번하게 변동하게 되므로 전기추진시스템의 전력변환장치에서 전류 및 전압파형에 고조파가 크게 포함되어 발전기, 변압기, 컨버터, 인버터 및 추진전동기에 손실의 증가, 기기의 열화 및 토크 맥동 발생 등의 좋지 않은 영향을 미치게 된다. 본 연구에서는 선박의 운항 환경에 따른 추진시스템의 전류 및 전압파형에 포함되는 고조파 함유율을 분석하였다. 분석 결과 저속 영역에서의 잦은 속도 및 부하 변동에 따라서 전동기에 공급되는 전류 및 전압 파형에 포함된 총 고조파 왜형율과 전동기의 토크 맥동이 증가됨을 확인할 수 있었다.

Animism was prevalent among people when Protestant missionaries first came to Korea. Since then, Protestant mission brought in great results among Koreans characterized by worshipping spiritual beings. Therefore, by examining the conversion pattern carefully in the materials written by missionaries as well as Korean Christians, one can easily find the significance of “power encounter”. Korean animists are very conscious of “power,” which is believed to be located in the spiritual beings, i.e. gods, ancestors and ghosts. Korean animists believe that the world is populated with lots of spiritual beings surrounding their environment. They not only have lots of traditions related to spiritual beings, but also serve many spirits in homes as well as in their villages. They are afraid of the spiritual beings and try to have good relationships with them. They also believe that anger or jealousy from the spiritual beings cause their everyday calamities. To overcome the problems, they either have to propitiate the spiritual beings with food or materials or coerce them through more powerful spiritual beings. In this context of spirit worship, the Gospel was very difficult to be accepted wholeheartedly by Korean animists. When they thought about accepting the Gospel, they had to deal with the retaliation from the spiritual beings they had formerly served. To accept Christ, they had to confront those spiritual beings. As soon as they accepted the Gospel, the title of the spiritual beings became negative such as “Satan” or “devil”. So they burnt fetishes like clothes, potteries, papers which were considered as the locations where the spiritual beings reside. Burning those fetishes terrorized lots of people who gathered around. Those who accepted the Gospel through such confrontation initially met persecutions from their family as well as their neighbors. But the early Korean Christians had persevered and ultimately overcame persecutions. Only when the family which had burnt those fetishes survived and ever thrived through the processes did family members confirm that God is more powerful than the spiritual beings. The story of the “power encounter” ran rapidly through relatives and neighbors. These kinds of illustrations of “power encounter” resulted in a paradigm shift among the people. They decided to accept the Gospel and became Christians. In short, “power encounter” engendered “people movement” toward Christ. Missiologist Alan R. Tippett’s thesis, the conversion of the animists are through the power encounter types of evangelism, is firmly proved by examining the Korean animists. As Tippett mentioned through his research among Melanesians and Polynesians that “power encounter” brought about “people movement” toward Christ, so did “power encounter” among Korean animists also result in “people movement” toward Christ. Although the animistic beliefs among Koreans nowadays are reduced in comparison to the period of first Protestant missions, many Koreans still resort to divinations and shamanistic rituals. Even many Buddhists seem to have animistic belief rather than the pure Buddhistic concept or perspective. So to approach the Buddhistic people with the Gospel, one has to be prepared with God’s power rather than with one’s knowledge about Buddhistic philosophy. Lessons we received from the Korean animists’ conversion experiences could be wisely applied when we evangelize the Buddhistic people. However, many cases of syncretism and backsliding to heretical movements are also found in Korean church history. When the process of “power encounter” is neglected or by-passed, chances of falling into such pitfalls are high. Without vivid confrontation with the deities which were served before, they cannot commit wholeheartedly to Christ. They can easily slide back to their traditional beliefs and become victims to heretical movements. To escape such negative influence from traditional belief systems, God’s servants working among animists have to examine carefully not to miss nor by-pass the process of “power encounter”. Also they have to consider carefully how to nurture believers with animistic backgrounds. Without appropriate nurturing, new believers with animistic backgrounds can easily backslide to their traditional beliefs. Upon the Word of God, their animistic perspectives and value systems have to be transformed to fit into the Biblical ones. Korean people were blessed when they accepted the Gospel and became God's people. They realized their mission sincerely and have tried to fulfill the great commission. They tried to be used by God especially for the worldwide evangelization. Even today there are many animists all over the world. For them, Koreans' experiences of turning from animists to God's people, can be utilized strategically. One who is thinking about evangelizing the animists over the world can use the “power encounter“ tactics and become a faithful servant of God. The conversion patterns of the Korean Christians can be used effectively in evangelizing the animists of the world when they get wisdom from early Korean Christians’ experiences.