How to connect three phase electricity and what safety issues to pay attention to

If you reverse, you can change the position of two of the 3 fire strips of the power cord, that is, you can change the phase of the power cord to change the direction of the induced current of the motor, so as to achieve the purpose of changing the motor steering, and then check that the motor is not a problem first, and the test time should be as short as possible, because the motor can not be reversed in some occasions.

The three wires can be connected at will, and if the motor is not turned right, any two wires can be reversed.

The red one is connected to the live wire, the blue one is connected to the zero wire, and the black one can also be left unconnected.

1. The difference between three-phase power supply and single-phase power supply: the power supply sent by the generator is three-phase, and each phase of the three-phase power supply and its neutral point can form a single-phase circuit to provide users with power energy. Note that it cannot be called the positive or negative electrode in the AC circuit here, but should be called the line end (called the live wire in civil electricity) and the neutral wire (called the neutral line in civil electricity).

2. According to the regulations, the neutral point of the 380 volt (three-phase) civil power supply should not be grounded at the entrance end (grounding at the transformer end, this grounding is to take into account that the point above the power supply voltage can not be caused by the suspension point, and the grounding of the user end and the grounding of the transformer end have a certain resistance in the earth), and the power supply mode is a live wire and a neutral wire (neutral point lead wire) to form a circuit, and there is also a grounding wire in the single-phase three-core power jack. This is taking into account the realization of the function of the leakage protector, (the working principle of the leakage protector is: if the human body touches the wire end of the power supply, that is, the live wire, or the internal leakage of electrical equipment, then the current flows from the live wire through the shell of the human living electrical equipment into the earth, and does not flow through the zero line, the current of the live wire and the zero line will not be equal, and the leakage protector immediately trips to protect the safety of people and electrical appliances after detecting this part of the current difference, and generally this difference current is selected in tens of milliamperes) if, If the neutral point of the power supply is directly grounded (which is not allowed in civil power construction), the leakage protector will lose its effect and cannot protect people and electrical equipment from short circuits.

People often use three-pin sockets in their lives, they are connected with three-phase electricity, but the danger of wiring is extremely high, it is best to go through a certain measurement and then wiring, and to understand the overall line, otherwise it is difficult to connect the wire. Only the slag Ling Qi has the wire to be connected to the normal use, the electricity and the socket is not a simple thing, the voltage of the home circuit is 220V, there is a strong threat to the human body, here we will take a look at how to connect the three-phase electricity socket to be safe?

Analysis of three-phase socket wiring

Generally, single-phase electrical equipment, especially mobile electrical equipment (such as refrigerators, washing machines, etc.), should use three-pin plugs and matching three-pin sockets. When using zero protection, it is extremely dangerous for someone to connect the terminal head of this hole directly to the neutral wire that is introduced into the socket only in the bottom of the socket. Because in case the neutral wire of the power supply is disconnected, or the fire (phase) wire and neutral wire of the power supply are reversed, the metal parts such as the shell will also carry the same voltage as the power supply (that is, the refrigerator shell is charged 220V), which will lead to electric shock.

How to connect three-phase electricity to the socket is safer

When the three-pin socket is wiring, there are generally three wires: live wire, neutral wire and ground wire. The socket port faces itself, and the only one on the top is the protective grounding wire (that is, it can prevent the leakage of the electrical shell from causing electric shock), and the next two are "left zero and right fire". The key is to protect the connection of the grounding wire.

1. Connect a special grounding device. If there is no special grounding device, you can make a steel bar into the ground and connect the wire to make a simple grounding device. Lead the wire of the homemade ground wire to the rear of the socket to protect the wire.

2. The protection line behind the socket is directly connected to the zero line of the inlet line. Remember not to connect to the neutral wire at the same socket n, although they are similar in principle. It should be noted that:

Many people are inconvenient, or the construction unit asks for trouble and does not accept it. There are also some people who think that the switch has leakage protection, and it doesn't matter if you don't need to connect it. According to the actual incident, it is still unsafe to not connect, and there are incidents of being shocked.

If it is not connected, due to leakage or static electricity, etc., children, women, the elderly and people with small human body resistance will still be shocked. Especially children, there was an incident where a child was knocked down by a cupboard handle flashlight, and we touched it without incident. In addition, leakage protection also has a trigger value and the problem of device failure.

Therefore, it is recommended to ground as much as possible as required.

The three-hole socket is safer after being connected, but even if it is relatively safe, it will be dangerous, and it is better to design the socket as high as possible in ordinary life, especially if there are children at home. The wiring methods introduced above must be kept in mind, and if there is no problem with the wiring, do not easily try to change the circuit. Three-phase electrical sockets will be a little more difficult, if you can't do it yourself, you can also spend some money to hire professionals to help us wiring.

You can get it for free

Three-phase electrical connection methods include: three-phase four-wire system (three-fire and one-zero) and three-phase five-wire system (three-fire and one-zero).

General Notes:

The metal casing of electrical equipment (e.g. electric motors) should be connected to the neutral line of the three-phase four-wire line.

Three-phase five-wire lines are more reliable by using protective grounding (i.e., connecting the metal shell of electrical equipment to the grounding body).

The metal shell of electrical equipment (such as electric motors) is connected to the neutral line of the three-phase four-wire line, which is called zero connection protection.

Protective Zero: Connect the lead wire from the electrical equipment housing to the neutral wire of the power supply. Because the three-phase load current of three-phase electrical equipment is basically balanced, and the neutral line current is small, the factory often uses a protective zero.

However, the three-phase current fluctuation of the civil electricity network is large, so it is not suitable for protection to zero, and the general use of protection grounding is more reliable.

Or another protection method is to connect the metal shell of the electrical equipment to the grounding body, which is called grounding protection.

It is not safe for electrical equipment, such as electric motors, to be connected to zero or ground.

Three-phase electricity, also known as power electricity, is composed of three live wires, without a neutral wire, and belongs to 380V alternating current, which is usually used for electricity consumption in factories and enterprises. Single-phase electricity is commonly used in households, that is, 220V alternating current composed of a live wire and a neutral wire. Typically, any combination of live and neutral wires used for a three-phase power supply can form a single-phase power supply.

The difference between three-phase electricity and two-phase electricity is that the power supply emitted by the generator is three-phase, and each phase of the three-phase electricity and its neutral point can form a single-phase circuit to provide users with power energy. In this AC circuit, it is not called a positive or negative pole, but a wire end and a neutral wire.

Three-phase electrical wiring.

Three-phase electricity has two connections: star and triangle at the power supply end or transformer and load side.

1. Star connection. The star connection method of three-phase electricity is to connect one end of each phase power supply or load to one point, and the other end of them is used as a lead-out wire, which is the three phase wires of three-phase electricity. The star connection method can lead out the midpoint as a neutral line to form a three-phase four-wire system.

or not to draw out, constituting a three-phase three-wire system. Regardless of whether there is a neutral wire or not, a ground wire can be added to become a three-phase five-wire system or a three-phase four-wire system, respectively. In the three-phase electricity of the star connection, the line voltage is several times that of the phase voltage, and the line current is equivalent to the phase current.

When a three-phase load is balanced, no current flows over the neutral wire, even if it is connected. When the three-phase load is unbalanced, it is necessary to connect the neutral wire to avoid the unequal voltage division of the load of each phase.

2. Triangular jointing. The triangular connection method of three-phase electricity is to connect each phase power supply or load end to end in turn, and at the same time lead out each connected point, which is used for the three phase wires of three-phase electricity. The triangle connection method does not have a neutral point and cannot lead to a neutral line, so there is only a three-phase three-wire system.

After adding the ground wire, a three-phase four-wire system can be formed.

Precautions for three-phase electrical wiring.

1. The load of the meter can be used to meet the requirements of the inductance coil with different conversion ratios. For example, if the inductor coil of the meter is 3x1(2)a, and the conversion ratio of the inductor coil is 1:50, the maximum rated current that can be carried by each phase is 100A.

2. According to the regulations, the neutral wire of the 380V civil power supply should not be grounded at the inlet end. If the transformer is grounded, this grounding is due to the fact that the potential above the power supply voltage cannot be caused by the suspended potential, and there is a certain resistance between the ground of the user and the ground of the transformer. The power supply mode is a live wire and a neutral wire, that is, the neutral point lead wire, forming a loop, and there is also a grounding wire in the single-phase three-core power jack.

The power supply and equipment connection should be consistent, which means that you are tn--c, you connect tn--s and tn--s--c, pay attention to the connection.

At present, the three phases of China's three-phase electricity are all 50Hz sine waves, and their voltage phases are 120° apart. If it is a three-phase three-wire system, and the load is a resistive load, the current will also be a sine wave of 50Hz, and the phase difference of the three-phase current is 120°.

Short circuits are divided into single-phase grounding short circuit, two-phase short circuit, two-phase grounding short circuit, and three-phase short circuit. The first three belong to asymmetric short circuit, which can be calculated by using the symmetrical component method to obtain positive, negative and zero sequence currents, and the superposition of the three currents is the size of the short-circuit current. The specific size of the calculation depends on the parameters of the circuit, and the current we usually refer to as the "effective value" rather than the instantaneous value.

Therefore, even if the current has a zero-crossing point, it cannot be said that it occurs intermittently, but that it should be continuous (before the short circuit is eliminated).

The direction of the current is defined as the opposite direction of the movement of the electrons, while the current of a metal conductor is formed by the directional movement of free electrons, and the current of a liquid is formed by the directional movement of positive and negative ions. The instantaneous value of the current in the circuit is zero, which cannot be said to be the neutralization of positive and negative charges, but the directional movement speed of the electrons at this moment is zero.

If the motor is connected, it is necessary to realize one-time protection control through circuit breakers, contactors, protectors or soft starts, inverters, etc., and the motor winding connection method is **.

Other loads send three-phase 380V power supply, 220V power can be provided through the neutral line, and only two-phase can supply 380V power supply, which can be selected according to the needs of the load.

When connecting to three-phase electricity, due to the phase sequence, it is possible that the motor is reversed, and two of the phases can be adjusted arbitrarily.

The principle is the principle of three alternating currents, that is, the three live wires are output by star connection or angle connection, but the power supply is generally star connection, and the motor is generally corner connection, and the two cannot be connected wrongly, otherwise there will be an accident.

We rarely use three-phase electricity in our lives, we usually use single-phase electricity, as long as we wiring specifications, use specifications, generally there will be no danger.

The load of the meter can be met by selecting inductance coils with different ratios. For example, if the meter distribution inductor coil with a specification of 3x1 (2)A is used, and the conversion ratio of the inductor coil is 1:50, the maximum rated current that can be carried by each phase is 100A.