Look, what you are talking about is a household three-pin plug, which is actually a live wire, a neutral wire and a ground wire. A live wire and a neutral wire constitute the power supply of the electrical appliance, and a ground wire is not actually connected to the circuit. It is connected to the shell of the electric appliance. Once the electric appliance leaks, the ground wire can drain the current into the earth to prevent people from getting an electric shock. If a leakage protector is installed at home, you can cut off the power immediately.
In the power supply system, the user terminal is not allowed to be grounded with zero line except that the transformer allows zero storage grounding. If the family connects the zero line and the ground line together, it may sometimes cause the electrical shell to be charged.
The grounding wire is not grounded, but connected to the ground to a certain depth to ensure reliable grounding. When the building is completed, the ground wire has been connected, which belongs to the electricity safety organization and should be used correctly. Self-built houses can be built according to specifications, and there is no reliable grounding device. Otherwise, once leakage occurs, it may pose a threat to personnel. Nowadays, many people don't care about the use of ground wire, thinking that it doesn't matter whether it is used or not. That is luck and danger.
Question 2: Why use three-phase electricity? Three-phase electricity is "single-phase electricity with a phase difference of 120 degrees". For this reason, four wires can transmit three times the single-phase electricity. If the three phases are balanced, the fourth wire (the middle wire) can be omitted because no current flows.
In addition, a more important reason for using three-phase electricity is that it can directly produce the minimum number of phases of the rotating magnetic field with clear direction and large starting torque. At present, the most common three-phase asynchronous motor is famous for its simple structure and powerful power, which benefits from the application of three phases.
Question 3: Why use three-phase power transmission? Three-phase AC transmission is the most economical in all aspects-transmission cost (in the case of using one more line, the transmission capacity is three times that of single-phase transmission); Manufacturing cost of power generation, substation and electrical equipment; The most important thing is that the load of power users is mostly three-phase power load, and the manufacturing cost, operating cost and equipment volume of three-phase AC transmission of power transformers and motors are the simplest, so three-phase AC transmission is adopted when formulating standards.
Question 4: Why do household circuits use alternating current? What's the difference between DC and AC? Alternating current is the current generated by the rotation of the generator. When the rotor rotates, the relative position between the magnetic pole and the stator coil changes constantly, and the current with changing size and direction is generated in the coil, which is alternating current. When the DC generator rotates, the rotor rotates continuously, so the output current is always in one direction. The instantaneous value of alternating current changes in size and direction at any time, while the direction of direct current remains unchanged. Alternating current has been widely used in various fields of production. And DC is mainly used in electroplating, electrolysis, various amplification circuits, DC motors (convenient speed regulation) and various portable devices. Why do household circuits use alternating current instead of DC? At present, household electrical equipment is basically alternating current, and the electricity generated by power stations is also alternating current, which is more convenient to transfer. The electricity generated by the generator can be used by users after being boosted by the transformer and stepped down by the transformer. This transmission itself consumes less energy, so household circuits should use alternating current. (answer with high school knowledge)
Question 5: Why use alternating current? People choose alternating current for many reasons. The most important thing is:
Electricity is transmitted over long distances. The transmission line has resistance, so it can't be very big. In order to improve the transmission power and reduce the loss, it is necessary to increase the transmission voltage (the same current, the higher the voltage, the greater the power) and reduce the voltage of the user. Many electrical appliances are designed to choose different voltages. Alternating current can be easily stepped up and stepped down through a transformer to meet the needs of users.
Many consumer appliances need alternating magnetic fields. For example, it is very simple to directly generate rotating magnetic field with three-phase alternating current, and vibration machinery can directly generate it with alternating current.
Alternator and alternator are simple in structure.
Question 6: Why do you need alternating current? Alternating current is easy to transmit (the step-up and step-down equipment is simple, which is convenient for long-distance high-voltage transmission)
Ac equipment is easy to use, and the structure of AC motor is much simpler than that of DC motor, so there is no need for commutator! (Three-phase AC electric energy generates rotating magnetic field) AC power conversion is convenient, suitable for long-distance transmission, and high-voltage transmission loss is low.
The same principle, because it can be easily converted into the required low voltage, AC or DC power supply circuit for use. Transforming DC is relatively difficult and costly.
In addition, industrial power equipment is generally AC equipment, which can directly use AC. The structure of AC motor is much simpler than that of DC motor, with much lower cost and higher efficiency. In order to facilitate power transmission, alternating current is used.
Some motors use DC, others use AC.
Question 7: Why do people use alternating current? The alternating current generated by generators in power plants can be changed by transformers. Substation transforms high voltage (such as 10000 volts) into AC 220 volts through transformer. Most of our household appliances use alternating current. Alternating current has many advantages, and the required voltage can be easily changed by transformer. Convenient for long-distance transportation. The AC motor has a simple structure. Three-phase AC can generate rotating magnetic field, and the structure of three-phase AC motor is simple. Where DC power is used, rectifiers can be obtained from alternating current. DC transmission technology is difficult to manufacture high-power converter. This is a technology that has only begun to be applied in modern times.
Question 8: Why do you use three-phase and four-wire for home power supply? No, home power supply is generally three-phase alternating current in single-phase power supply, which is a transmission form of electric energy, referred to as three-phase electricity. Three-phase AC power supply consists of three AC potentials with the same frequency, equal amplitude and phase difference of120. Three-phase alternating current has many uses, and most industrial alternating current electrical equipment, such as motors, adopts three-phase alternating current, which is commonly called three-phase four-wire system. In daily life, single-phase power supply is often used, which is also called lighting power consumption. When lighting is powered by electricity, one of the three-phase electricity is used to supply power to electrical equipment, such as household appliances, and the other is the fourth line of three-phase four wires, that is, the zero line, which leads out from the neutral point of three-phase electricity. A three-phase generator is called a three-phase power supply; A circuit powered by a three-phase power supply is called a three-phase circuit; U, V, W (formerly known as ABC) are called three phases, and the phase-to-phase voltage is line voltage, and the voltage is 380 V; The phase voltage between the phase line and the neutral line is called phase voltage, and the voltage is 220V V V.