There are three live wires in the three-phase electricity used by the water pump, namely phase A, phase B and phase C. The colors are green and red in order.
1. Three-phase four-wire system
In the low-voltage distribution network, the transmission lines generally adopt the three-phase four-wire system, in which the three lines represent the three phases A, B and C respectively, l The other is the neutral line N, so it is called a three-phase four-wire system.
In a three-phase four-wire power system, if the neutral line is not grounded well or the ground terminal is broken, the consequence is that the potential of the neutral line is not equal to 0 when the three-phase load is unbalanced and the neutral line potential is not equal to 0. This means that the neutral point is moving. The specific potential of the neutral line is related to the degree of unbalance of the three-phase loade. The more unbalanced the neutral point, the greater the neutral point offset and the higher the neutral line potential. .
2. Three-phase five-wire system
Three-phase five-wire system refers to lines A, B, C, N and PE. Among them, the EP. The line is the protective earth wire, also called safety wire, specially used to connect to devices such as equipment shells to ensure electricity safety. The PE line is connected to the N line on the power transformer side, but it should not be used as the neutral line after entering the user side, otherwise it will be the same as the three-phase four-wire system after chaos. occurs.
Detailed information:
Three-phase electrical characteristics: < /p>
Three alternating currents of equal size, same frequency and initial phase difference of 120° form a three-phase alternating current. Actual three-phase alternating current is generated by a three-phase generator. In the generator there are three identical windings distributed evenly with a spatial difference of 120°.
In this way, the rotation of the generator can produce three single-phase alternating currents that meet the above conditions. Since the initial phase difference is 120°, there is a time difference in the current flowing through each. wire, so six wires are not needed. To power, you simply connect the three windings in a certain way inside the generator and use three or four wires to power.
The alternating current emitted by each winding of the generator is called one phase of the three-phase alternating current, which is the single-phase alternating current we use. The three-phase windings of the generator are respectively called phase A winding, windingphase B and phase C winding.
We connect the rear end of one winding to the first end of another winding, then connect the rear end of the other winding to the first end of the next winding. The three windings are connected in a circle. Connecting one line from each contact is called a delta connection, connecting the ends of the three windings together, and connecting one line from each leading end is called a star connection.
Baidu Encyclopedia-Three-phase electricity
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