How to measure whether the three-phase electricity is out of phase with a multimeter
Three-phase electrical phase loss means that one or two of the three phase lines have no voltage. When the user uses electricity, if only one phase wire is taken, and it happens that this phase wire is out of phase, then the user end will have a power outage. If it is a three-phase electrical equipment, it can still be used after one phase is missing, but it will cause voltage instability, which is easy to rise or fall suddenly.
In the three-phase electricity, the voltage of the phase line to the ground and to the neutral line is 220V. Use the voltage file of the multimeter to measure the voltage between the three phase wires and the ground or neutral wire in sequence. Under normal circumstances, it should be about 220V. If the voltage is 0 or too low, it proves that the phase line is out of phase.
The voltage between the phase lines should be about 380V. Measure the voltage between AB, AC, and BC in turn. If the voltage is far less than 380V, it proves that at least one of the two phases measured is out of phase.
How to distinguish the ground wire, zero wire and live wire with a digital multimeter
The distinction between the neutral wire and the ground wire can be distinguished according to the wire diameter. Generally speaking, the neutral wire as the main circuit transmission line is the same thickness as the phase wire, and the ground wire is relatively thinner. Of course, this is not absolute. The general thickness of the ground and fire zero line configuration. In addition, we can also use a digital multimeter to measure the voltage of the two wires to the ground. The higher voltage value is the neutral wire, and the lower or zero voltage is the ground wire. The following is the specific operation method.
First, we prepare a basin of water, set the gear of the multimeter to the AC voltage gear, then connect one of the test leads of the multimeter to the line under test, and put the other into the water, and read the values respectively. The higher value is zero. The lower value is the ground wire.
As for why both the neutral line and the ground line are grounded, but the measured value of the multimeter is high or low? This is because in the actual circuit, the distance between the neutral line and the ground terminal is relatively long, and there is line resistance in the line. The tiny voltage value we measure is actually the voltage drop of the line resistance of the neutral line. The ground wire is grounded nearby, so the resistance of the wire is smaller than that of the neutral wire, so the voltage value we measure is smaller than that of the neutral wire.
