According to the standards of the industrial waterproof electrical industry, the number of cores for industrial plugs is mainly divided into three types: 3-core (2P+E), 4-core (3P+E), and 5-core (3P+N+E). Executive standards: German industrial standard DIN VDE 0623, European/international standard EN/IEC 60309-2. Choose industrial plugs with different numbers of cores under different working voltage environments. For example, if the industrial voltage is single-phase (220V), choose a 3-core; The industrial voltage is three-phase (380V), choose 4-core or 5-core.