Electrical knowledge (electrician)

The problem lies in a device that uses 220V AC power supply and has a metal shell. Its metal shell should have safety protection grounding wire. Simply put, the power plug of this equipment should be connected to the power supply with a "single-phase three-wire" plug. "Three lines" refers to "live line" and "zero line". These two wires provide 220v power supply, and there is also a "connecting wire" to be connected to the metal shell of the equipment. The equipment has a "ground wire" for safety protection. No matter whether there is leakage on the 220v circuit or the 12v DC circuit, the electric shock accident can be avoided if the metal shell is well grounded in the socket. If the electrical equipment powered by commercial power supply has a metal shell or is exposed, users may come into direct contact with the exposed metal parts. Generally, the grounding wire should be installed on metal components, so it is not advisable to remove the grounding wire for use, because it will increase the unsafe factors, that is, there is a greater risk of electric shock, which is not desirable as a product design.