Use a 220V test pen to check accuracy. The international convention for a three-core socket is zero on the left, fire on the right, and ground in the middle. The four-conductor one has three-phase electricity, the bottom three are three live wires, and the top-middle one is usually a ground wire. There are also three fire connections and one zero connection. You can use an electric pen to detect live wires. The range of a multimeter should be greater than 380 V. The voltage between two live wires is about 380 V and the voltage between zero live wires is about 220 V. If the motor driven by the output turns at upside down, simply swap two live wires. Remember to turn off the power and pay attention to safety.
If the outlet is marked, L1L2L3 is the live wire, N is the neutral wire, and if there is an E, it is the ground wire.
Place a card and a prifive pin with three lights, a zero and a ground wire.