Why is alternating current three phase instead of four phase or five phase ?

Because the generator is three-phase.

Three-phase four-wire system.

What is the difference between the three-phase three-wire system?

Generally, the practical application is only three-phase four-wire system (not counting the ground wire, counting the ground wire is called three-phase five-wire.)

system), will not use the three-phase three-wire system.

In addition to the three live wires of the three-phase four-wire system, the fourth is called the middle line (note: the single-phase has a zero line, and the three-phase does not), and the middle line plays a role in ensuring the load phase voltage.

The effect of the time is unchanging.

If a three-phase circuit.

The load connected to each of them is the same, and the sum of the currents flowing through the center line at each moment is zero, so it is possible to remove the center line and use the three-phase three-wire system for power supply. However, this is an ideal situation, and in practice it is impossible for a three-phase load to be perfectly symmetrical in a three-phase circuit with multiple single-phase loads connected to a three-phase circuit. In this case, the midline is particularly important and not optional.

If there is no center line in the case of asymmetrical load, the three-phase three-wire power supply of asymmetrical load is formed. Due to the asymmetry of the load impedance, the phase current is also asymmetrical, and the load phase voltage is naturally not symmetrical. Some phase voltages may exceed the rated voltage of the load.

The load may be damaged (the bulb of the phase is too bright and burned); Some phase voltages may be lower and the load may not work properly (the bulb is dim). With the light on, the light off and other reasons cause the change of the load impedance of each phase. The phase current and phase voltage all change accordingly, the lights flicker and flicker, and other electrical appliances cannot work properly, or even be damaged.

So there must be a center line, that is, a three-phase four-wire system.

The 3 phase is the smallest number of phases that can produce a stable rotating magnetic field without the use of auxiliary equipment, and if it is also possible with , 360 is divisible by the natural number.

You can, of course, the more the better, but one more phase means more wires, transformers need more cores, substations need more than one set of circuit breakers, and more scheduling requires more sets of monitoring, which is expensive! Since the 3-phase can generate a rotating and stable magnetic field, and it has also been popularized, and the efficiency is still high and cheap! Then use them all.

1. The difference in power supply mode. Single-phase electricity refers to the form of electrical energy transmission composed of a phase wire (commonly known as a live wire) and a neutral wire. The power supply circuit composed of two phase wires is called two-phase power supply, referred to as two-phase electricity.

Three-phase alternating current is a form of transmission of electrical energy, referred to as three-phase electricity. Three-phase AC power supply is a power supply composed of three alternating currents with the same frequency, equal amplitude, and 120° difference in phase.

2. The difference in voltage level. Three-phase electricity is a phase-to-phase voltage of 380V. The two-phase electricity is 220V. The single-phase is 220V, which is the voltage between the phase line and the neutral line.

3. Differences in use. Three-phase electricity is used to power enterprises and factories, such as motors, pumps and other large equipment. The two-phase is mostly used in the use of household appliances such as homes, schools, and hotels.

Single-phase electricity, two-phase electricity, and three-phase electricity are the names used in low-voltage three-phase four-wire (380V 220V) power supply systems.

4. The difference in the number of wires. Three-phase electricity has two more live wires than two-phase electricity, and single-phase electricity is composed of one phase wire and one neutral wire, and the voltage is 220V.

5. The difference in connection methods. Three-phase electricity can be connected to the motor, and three of them enter the motor at the same time, and there are star connections and triangle connections. In a single-phase system, there are only two wires.

Power is measured using a power meter. In a three-wire system, two power meters are required. Two-phase electricity is a multiphase alternating current system in the early twentieth century.

The generator has two windings and the output voltage is orthogonal. The system typically has four wires, two for each phase. Sometimes, the midline is shared, so only three lines are needed.

1. The difference between three-phase electricity and two-phase electricity is that three-phase electricity has two more live wires than two-phase electricity, and the voltage level is different.

2. Three-phase electricity is 380V, two-phase electricity is 220V, three-phase electricity is also used in enterprises and factories, such as motors, pumps and other large equipment power supply, and two-phase is mostly used in households, schools, hotels and other household appliances.

3. Two-phase electricity and three-phase electricity are the names of low-voltage three-phase four-wire (380V 220V) power supply systems.

Single-phase means that the neutral line (neutral line) is composed of any phase wire (A, B, C) with a voltage of 220V. Two phases represent any two phase lines (AC, AB, BC) with a voltage of 380V. Three-phase represents a three-phase (A, B, C) line with a difference of 120 degrees, 3 380V.

For electrical loads, there are two types of connection (star and triangle) for the three phases.

Ask me a question: If the three-phase electricity is connected to a two-phase meter and three pieces, what will happen?

Can I ask a voice consultation?

Question: I use three-phase electricity, and the landlord uses three pieces for me to connect a two-phase meter, is there a difference?

Three two-phase meters were used.

Question: Will there be an error in a two-phase meter for three-phase electricity?

Three-phase electricity with two-phase meters, will there be errors.

The key to the question is a three-phase electricity, he uses a two-phase three-meter meter, which is calculated together, will there be any error in this?

1. In the general common transmission line, there is no three-phase power supply, but when the three motors are used, the two power lines are converted into three power sources without zero line through the power distribution device.

This is what the electrical engineer focuses on, and the three-phase power supply is achieved through three conversion circuits. Generally, the so-called three-phase electricity refers to the electrical power supply of 380V industrial equipment, which is a two-phase power supply;

It is set to two fire lines and one zero line, which is the system of two fires and one place.

It should be called biphasic or binomial electricity and is used by commonly used electrical equipment.

The phase here is the live wire that does not include the neutral wire, and the neutral line is not considered a one-phase power supply.

2. If you use a single live wire and a neutral wire, it is a single power supply of 220V.

A single power supply, generally a 220V power supply for lighting or household electrical use.

3. The live wire is the power line, and the neutral wire is the power circuit.

There is no single item of electricity without a circuit.

A bunch of copied wrong answers.

If it is 3*220 380V three-phase electricity, the two-phase is 380V, the single-phase is 220V, the two-hole and three-hole sockets at home are single-phase electricity, and the difference between the three phases is 120°. Generally, it is rare to see two-phase electricity, Japan and the United States have household electricity, and the two-phase electric voltage is also more than 200V, but at this time, the single-phase is only more than 100V, and the difference between the two phases is 180°

There is a difference, three-phase electricity is larger than two-phase electricity and single electrical load.

The difference between two-phase electricity and three-phase electricity isFirst, the voltage level is different.

1. Two-phase electricity: The voltage of two-phase electricity is 220V.

2. Three-phase electricity: The voltage of three-phase electricity is 380V.

Second, the use is different.

1. Two-phase electricity: Two-phase electricity is generally used in schools and homes.

2. Three-phase electricity: Three-phase electricity is used in factories and enterprises.

Third, the characteristics are different.

1. Two-phase electricity: The two windings will be installed evenly in the generator, that is, the cross type. So, the output voltage differs by 90 degrees, not 180 degrees.

2. Three-phase electricity: When lighting electricity is used for power supply, one of the three phases of electricity is used to supply power to electrical equipment, such as household appliances, and the other wire is the fourth wire in the three-phase four-wire system, that is, the zero line, which is drawn from the neutral point of the three-phase electricity.

Three-phase alternating current is characterized by the saving of wires in power transmission and the generation of rotating magnetic fields.

Three-phase alternating current is generated by three sets of symmetrical windings of a three-phase generator, and each winding together with its external circuit is called a phase, which is recorded as a, b, and c respectively. Their combination is called three-phase system, and they are often supplied with three-phase three-wire system and three-phase four-wire system, that is, triangular connection and star connection.

The main advantages of the three-phase system are: saving wires in power transmission; It can generate a rotating magnetic field, and creates conditions for the development and application of asynchronous motors with simple structure and convenient use. The three-phase system does not exclude the supply of power to single-phase loads.

Therefore, three-phase alternating current has gained the most widespread application.