https://blog.gongquiz.com/2021/07/21/%ec%9e%90%eb%8f%99%ec%b0%a8%ec%9a%a9-%ea%b8%b0%eb%8f%99%ec%a0%84%eb%8f%99%ea%b8%b0self-starting-motor%ec%97%90-%ec%a3%bc%eb%a1%9c-%ec%82%ac%ec%9a%a9%eb%90%98%eb%8a%94-%ec%a0%84%eb%8f%99%ea%b8%b0/