Why should AC contactors use three phase four wires?

1. Because the electromagnetic coil of the AC contactor has 220 volts, a neutral wire is required.

2. Contactors are divided into AC contactors (voltage AC) and DC contactors (voltage DC), which are used in electricity, distribution and consumption. Contactor in a broad sense refers to the electrical appliances that use the current flowing through the coil to generate a magnetic field and close the contact to control the load in industrial electricity.

3. Three-phase four-wire system, in the low-voltage distribution network, the transmission line generally adopts the three-phase four-wire system, of which three lines represent A, B, C three-phase, and the other is the neutral line N (if the neutral point of the power supply side of the circuit is grounded, the neutral line is also called the neutral line (the old-fashioned name, which should be gradually avoided, renamed PEN, if not grounded, then in the strict sense, the neutral line cannot be called the zero line). In the single-phase transmission line entering the user, there are two lines, one we call the phase line L, and the other we call the middle line N, the middle line normally passes the current to form the circuit of the current in the single-phase line. In the three-phase system, when the three-phase is balanced, the neutral wire (neutral line) is current-free, so it is called the three-phase four-wire system; In the 380V low-voltage distribution network, the N-line is set up in order to obtain the 220V phase-to-phase voltage from the 380V phase-to-phase voltage, and some occasions can also be used to detect the zero-sequence current in order to monitor the three-phase power supply balance.

Because the electromagnetic coil of the AC contactor has 220 volts, a neutral wire is required.

Because the motor is a three-phase AC contactor, the low voltage should be used to adsorb to achieve low voltage and control high voltage

The coil needs n wires, and you can also use the contactors of the 380v coil, so it's three-phase.

Summary. If the three-phase load is balanced, then the three currents are equal, and the algebraic sum and addition of the three currents mean nothing; If the instantaneous values are added, the result is zero. If the three-phase load is unbalanced, the direct algebraic sum and addition do not represent any physical significance, because the phases of the three currents are different.

All, the calculation of the three-phase current refers to the line current i from the power supply side, which is used to characterize the magnitude of the three-phase load. In the two images above, i=p (380 3).

Whether the current of the three-phase AC contactor is added up by the three phases or single-phase.

If the three-phase load is balanced, then the three currents are equal, and the algebraic sum and addition of the three currents have no subtle meaning; If the instantaneous values are added, the result is zero. If the three-phase load is unbalanced, such as the algebraic sum and addition of Huai, it does not represent any physical significance, because the phases of the three oak slag currents are different. All, the calculation of the three-phase current refers to the line current i from the power supply side, which is used to characterize the magnitude of the three-phase load.

In the two images above, i=p (380 3).

Ha of single phase calculation.