Why is the neutral wire of the three wire and four wire system not allowed to be switched in series?

will increase"Break zero"the possibility that the switch is pulled apart. Poor switch contact.

Break zero"The 220V load on the three-phase four-line is equivalent to the star connection on the 380V, but the three-phase load cannot be balanced, and the one-phase voltage with a light load is the highest, which makes the 220V equipment on this phase burn out a lot.

Break zero"After that, it will cause the neutral line to ground voltage to rise, increasing the possibility of electric shock.

The neutral wire of the three-wire and four-wire system cannot be broken.

1.The neutral wire of the three-wire and four-wire system is used for protection and zero. If a switch is installed, when the switch is disconnected from the housing of the device and accidentally energized, it will cause an electric shock accident.

2.When the neutral switch is disconnected and the three-phase load is uneven, the load voltage of a certain phase will increase and the load voltage of a certain phase will decrease, and the load will be burned out in serious cases.

In addition, if the neutral line of the input line is disconnected at home, the voltage in some homes is very high (one phase) and some are very low (another phase), and the electrical appliances will be burned.

The reason why the three-phase four-wire system is adopted is that after a certain phase fails, the load of the other two phases can also maintain the original phase voltage at both ends for power supply, and the neutral point of the lead wire is to make each phase have a circuit. If a switch is connected in series at the pinout at the neutral point, when a phase fails, the short-circuit current will flow through the neutral wire, which will cause the switch to skip off. Cause the voltage of the remaining two phases to rise.

Not necessarily. In TN-C and TN-C-S, it is generally recommended to use the neutral wire through when frequent maintenance is not required.

In the case of frequent maintenance, in order to ensure safety, the neutral wire should be strung into the switch.

The three-phase four-wire circuit is used for protection on the middle line, and it is not allowed to install switches and fuses, otherwise the voltage of a certain phase may be high when the center line is disconnected, and the voltage of the other two phases is very low, which burns out the load. If the center line is removed, it is also possible, but the voltage between the phases must be equal.

If the series switch is opened, the following problems will occur: the equipment connected to zero protection will lose its protection at this time, just like not connected to zero.

In a three-phase four-wire system, can switches and fuses be installed on the neutral wire? It depends on what the grounding method is

If the N line of the TN-C system is shared with the protective grounding wire PE, that is, the PEN wire, the PEN line is not allowed to be cut off, that is, it is not allowed to install switches and fuses.

If the TN-S or TN-C-S system N wire is separated from the protective grounding wire PE, then the N wire is allowed to be cut off, that is, it is allowed to install switches and fuses.

A three-phase four-wire system refers to the form of a live conductor and does not include the type of grounding.

Three-phase four-wire system can be divided into TN-C, TN-C-S according to the form of grounding system, the three-phase four-wire system usually refers to TN-C system, and the three-phase five-wire system (from a professional point of view, is not accurate) usually refers to TN-C-S, or TN-S system.

The requirements of the specification are not allowed, because once the fuse is blown or the switch is damaged, the contact is poor and not conducted, the other phase passing load is high potential at the zero line of the open circuit, which is easy to cause the risk of electric shock.

It is not possible to install the fuse, the switch can be installed, but the live wire and the neutral wire should be fully connected in one switch, and the switch is open and separated at the same time.

In the three-phase four-wire power supply system, the neutral wire is not allowed to install switches and fuses

In the three-phase four-wire power supply system, when the three-phase load is asymmetrical, due to the existence of a neutral line, the three-phase each forms an independent circuit, and each phase load still obtains the corresponding power supply phase voltage, so as to ensure the normal operation of the load equipment, but the neutral current is not zero at this time. If the neutral wire is disconnected, although the line voltage of the three-phase power supply is still symmetrical, the neutral point of the load is displaced from the neutral point of the power supply, the phase voltage obtained by the load of each phase is no longer symmetrical, the voltage obtained by the phase with large load will be lower than the rated voltage, and the phase with small load will exceed its rated voltage, so that the normal operation of the load equipment is affected, and the accident may be caused when the serious imbalance is serious, and the electrical equipment will be burned. Therefore, in the three-phase four-wire power supply system, it is not allowed to install separate switches and fuses on the neutral wire to prevent the neutral wire from being disconnected.

The role of the neutral thread.

1. When the three-phase load is an unbalanced load, balance the voltage of each phase load so that the voltage of each phase is not too high or too low.

2. When there is a 220V two-phase power supply at the end, the neutral wire is used as the neutral line of the two-phase power supply.

3. When the protection is connected to zero, the neutral wire is the protection line.

Corresponding reasons for not allowing open circuits:

1. When the neutral wire is open and supplies power to the unbalanced load, it will lead to voltage imbalance, which will affect the quality of power supply and damage the equipment.

2. If there is a two-phase power supply, the two-phase power supply line at the end will be blacked out.

3. Using the system of protection zero connection, the open circuit of the neutral wire will make the protection zero connection invalid.

In the three-phase four-wire, the neutral line is the neutral wire, and for one of the phase wires in the three-phase wire, that is, the single-phase circuit, it is the "loop" line that provides the current of the phase wire, and if the neutral point is not grounded in the system, its voltage to the ground is not zero. The neutral wire refers to a "common wire" when the three phase wires are connected in the three-phase AC circuit of the "star connection", and in the strict absolute balance of the three-phase AC load, the neutral wire is zero potential, that is, the voltage is zero. However, in order to prevent the load from being "unbalanced" and the neutral wire is electrified, the neutral wire is grounded.

The grounding wire does not refer to the line in the current loop, it is a protective wire, the neutral wire is grounded, the neutral wire is grounded, and the equipment shell protection grounding and so on all refer to this wire, which does not participate in the operation of the equipment and does not provide the current loop under normal conditions.

If the neutral line is installed with a fuse or switching system, if the three-phase load is unbalanced, the current of the neutral line will be very large, and the fuse will soon be blown off, resulting in the neutral drift of the neutral line due to the operation of the zero line, which will immediately cause the voltage of the phase of the live wire to be low, and the voltage of the phase of the live wire with a small load is too high or even exceed the voltage of 220 volts, resulting in the voltage of the electrical appliances of this phase is too high and the current is too large and the electrical appliances are burned.

The switch or fuse is installed on the zero line, once the circuit is broken, first explain the two-phase electricity: it is equivalent to 380V voltage added to the original two-phase electrical appliances, and the two-phase electrical appliances are equivalent to series connection, at this time, the higher the resistance value of the electrical appliances, the higher the terminal voltage, then burn the electrical appliances with high terminal voltage, and burn off the electrical appliances with low terminal voltage.

When the neutral wire is disconnected, the neutral wire is energized when it is connected to the live wire through the load.