About the series loop current
Thread Content
I have a confusing question, Sichuan friends, please don’t laugh. Is the neutral line the line that returns to the power supply after the electrical equipment consumes power? If so, then the neutral wire and the live wire are in a series circuit, so their currents are equal. Why do many electricians say that the neutral wire has no current?
The potential of the neutral line is basically the same as that of the earth, and the ratio of the resistance of the human body to the resistance of the neutral line is very large, so the current flowing through the human body is extremely small. Under normal circumstances, it can be considered that there is no electricity. However, if the neutral wire is broken and a person touches the side of the broken live wire, a circuit from the live wire - electrical - human body to the earth is formed, and the electric shock potential is the normal voltage. At this time, the resistance of the human body is larger than the resistance of the electrical equipment.
The absence of current in the neutral line is a normal condition for the three-phase AC system. The presence of current in the neutral line indicates a power supply failure. The live wire and the neutral wire form a power supply loop. These are two different concepts!
Only when there is voltage can there be current. Compared to an AC single-phase circuit, because the main voltage drop is on the load, we can think that there is no electricity when touching the neutral line alone.
Partially agree with the point of view, the current in the neutral line and phase line of a single-phase power supply circuit is equal. In a three-phase power supply system, the voltage between two phases is 380VAC, and the voltage between any phase and ground (zero) is 220VAC. The three-phase voltages differ in spatial position by 120 degrees of electrical angle. So if the three-phase load is absolutely balanced, there will be no current on the neutral line. The current in the neutral line only indicates that the three-phase load is unbalanced, not a fault. For example, we have connected a single-phase load to a three-phase power supply system.