According to the standard industrial waterproof electrical industry, industrial plug some mainly divided into three types: 3 core (2 p + E), 4 core (3 p + E) and five core (3 p + N + E). Execution standard: DIN VDE 0623 German industrial standards, the European/international standard EN/IEC 60309-2. Under the environment of different working voltage, choose a different some industrial plugs. Such as: industrial is single phase voltage (220 v), choose 3 core; Industry is a three-phase voltage (380 v), choose four core or five core.