Star-shaped connection method and triangular connection method for three-phase electric power

The three-phase power supply three windings of the end, X, Y, Z joined together to become a common point o, from the beginning of a, B, C leads to three end-line, which is called "star-shaped connection method" also known as "Y-shape connection method." Three-phase power supply is the same frequency, the amplitude is equal and phase in turn 120 ° three sine power supply in a certain way connected to the external power system. The three-phase power supply connection method has the Y shape and the shape two kinds.
Star-Shaped connection method
is the three-phase power supply winding or the end of the load is connected to form a neutral line, due to a balanced three-phase electric current in the neutral line is zero, it is also called 0 Line: three-phase power supply winding or the other end of the load of the lead line, respectively, three-phase electric three phase lines. When transmitting remotely, only three phase lines are used to form three-phase wire system. To reach the user's circuit, often involving 220V and 380V two kinds of voltage, need three phase line and a 0 wire, forming a three-phase four-wire system. Users to avoid electricity leakage formation of electric shock accident, but also to add a ground, at this time there are three phase line, a 0 line and a ground, so there are three-phase five-wire system. Symmetrical three-phase four-wire y-y system is a common common system, there are three lines of fire, a median line. The three-phase electric line voltage is 3 times times the square root of the phase voltage, and the line current is equal to the phase current. When the three-phase load is balanced, there is no current flowing even when the neutral line is connected. Three-phase load imbalance, the neutral line should be connected, otherwise the load will be divided into different phases.
star-shaped connection is mainly used in high-voltage large-or medium-capacity motors, the stator winding only leads to three wires. For star-shaped connection, each phase load is balanced, then the current vector at any time flows through the three phases and equals zero.
Triangular connection method
The triangular connection method of three-phase electricity is to connect each phase power supply or load sequentially, and bring out each connected point as the three phase line of three-phase electricity. The triangular connection method has no neutral point, nor can the neutral line be drawn, so there is only three-wire system. After adding ground, it becomes three-phase four-wire system.
Triangular-connected three-phase electricity, the line voltage is equal to the phase voltage and the line current is equal to the phase current of √ 3 times times.
relationship
The relationship between the Star (Y) and the triangular () connection is close, and its load phase voltage, phase current and symmetrical three-phase line voltage and line current are as follows:
Star-Shaped connection method:
I-line =i phase, U-line =√3xu phase,
p Phase =u phase XI phase,
p=3p Phase =√3xu line XI phase =√3xu line XI line;
Triangular connection method:
I-line =√3xi phase, U-line =u phase,
p Phase =i phase Xu Phase,
p=3p phase =√3xi line Xu Phase =√3xi line Xu line.
Description: Triangular () join, Iab=ia vector +ib vector = (ia+ib) Xcos30°=2iax√3/2=√3xia, line current is three times times the square root of the phase current.
Another important application is the star-shaped connection of the resistor.
If the resistor constitutes a star-triangular (Y-) join, it is not possible to use strings or parallel equations for equivalent simplification, but they can be equivalent by exchanging equivalent formulas: (1, 2, 3 is the node, R12 represents the resistance between 1, 2 nodes, is the resistance of the Triangle joint.) )
220V and 380V
220V is the voltage between the FireWire and the 0-wire, called the phase voltage.
380V is the voltage between any two FireWire in a three-phase circuit, called the line voltage.
To increase the 220V to 380V in the three-phase four-wire supply circuit to take any two phase line (FireWire) on the line. Only the boost device (step-up transformer) is used to change the voltage in single-phase lines.
Power from the power plant to the city after the transformer is the three-phase four-wire electricity. You can find that there are four wires hanging on the poles, one of them is 0 lines, the term is neutral (N) and the remaining three lines are called FireWire. Two wires between the FireWire voltage is 380V, a 0-wire (N) and any one of the voltage between the FireWire is 220V. If you live in a city building, you can also see three FireWire and a 0 line being properly allocated to each unit. If you live in that unit of air conditioning and other electrical equipment especially, the power load is too large, using voltmeter to measure the voltage is significantly lower than the other low-power Danyuanlou voltage. Serious cause of electrical failure to start and operate normally.

Star-shaped connection method and triangular connection method for three-phase electric power