We may often hear the terms single-phase and three-phase electricity without understanding what they mean. In fact, they are both alternating current, and single-phase and three-phase electricity are two systems that we often see in our lives.
Single-phase electricity is a power transmission method consisting of only one fire wire and one zero wire. The fire wire is responsible for carrying the current, and the zero wire is responsible for providing a return path for the current, and the alternating current alternates between the fire wire and the zero wire, resulting in a sinusoidal waveform. Its output voltage is 110V, 60Hz or 220V, 230V, 240V, 50Hz.
Due to the sinusoidal structure of single-phase electricity, there will be peaks and valleys changing during the cycle, making its output power unstable. It is usually used in electronic equipment with small loads, such as: household appliances, commercial office equipment, medical equipment, etc.
Three-phase electricity usually consists of three fire wires and one zero wire. As with single-phase electricity, the three fire wires carry the current in and the one zero wire provides a path for them to return. The three fire wires represent the three phases, and the voltage phase difference between them is 120°. The existence of the phase difference allows the three-phase power to provide a stable power output and reduces the energy loss in the transmission process.
In three-phase electricity, alternating current reaches its maximum voltage in each branch. Its output voltage remains constant and never drops to zero. It is available in 380V, 400V, 440V, 50 or 60Hz, and can usually withstand larger loads, such as high-power motors, large commercial and industrial installations, and so on.
The star connection, also known as the Y-connection, is the more common connection and requires three fire wires and one zero wire for a three-phase, four-wire system. Each of the three phases is connected to a neutral, which is then connected to the zero wire. This connection allows one fire wire and one zero wire to be connected to the load, which can be used as three single-phase electrical systems to supply power to the load.
Triangular connection, which requires only three wires, is a three-phase, three-wire system. The phase head of a firewire is connected to the end of another firewire, in order to line connection, forming a triangle arrangement. The liabilities are then connected between the two fire wires, thus forming a load circuit. It cannot form a single-phase power supply for the home, and is only suitable for equipment that requires three-phase power supply.
4.1 A three-phase system provides a higher power output than a single-phase system and can be used for a variety of large equipment.
4.2 Single-phase electricity is more affected by load changes and the voltage tends to fluctuate, while three-phase electricity has less voltage fluctuation and a more stable power supply.
4.3 When small power single-phase electricity is applied to small household appliances, the cost is lower compared to three-phase electricity at the initial stage. Although three-phase electricity has a high cost at the initial stage, its three-phase alternator and transformer are more material-saving than those of single-phase electricity, and when applied to high-power electrical appliances, it can bring about stable and efficient power demand. It is more economically efficient in the long run.
4.4 Small motors usually can’t run on single power supply, in order to make the motors run stably, it is also necessary to apply the motor starter. And three-phase electricity can start by itself without external equipment. Compared to single-phase electricity, it is more economical.
Single-phase power and three-phase power have different configurations and different application scenarios. Through the above, from the power, efficiency, economic efficiency, applicable scenes and other specific analysis, to understand the difference between them, help to choose more suitable for our power, so as to ensure the stability of the power supply system.
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