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The consumer often does not think about which AC mains his apartment or private house is powered from. It can be a single-phase or three-phase connection. The primary consumers of electrical energy are devices designed for a voltage of 220 V. Now, and they began to produce and install household electrical equipment for 380 V. These are mainly electric stoves in high-rise buildings. And in private households, when arranging a workshop, machines are used to connect to a three-wire electric line. In this article, we will understand the differences between single-phase and three-phase voltage.
What Network are Our Houses and Apartments Powered From?
Most apartments and private houses use a single-phase electrical connection. In this case, the total consumer loads do not exceed 10 kW. The share of such connections accounts for about 90% of all electrical consumers.
The remaining 10% use a three-phase connection. It is used if necessary to connect a load with a power of more than 10 kW. For this, 380-volt alternating current networks are used.
These include residents of cottages or private houses and owners of apartments where electric stoves or other devices are installed that are designed to connect to 380 V.
The Main Differences
A common factor is the number of wires and voltage. It is where the differences end. A single-phase connection is characterized by connecting two / three wires to a house or apartment (phase, zero, ground). Usually, the cross-section of the conductors is 4-6 mm 2. In the house, they use wiring 1.5-2.5 mm 2.
At the same time, it is limited by the maximum power consumption, which should not exceed ten kW. Difficulties may arise with the connection of consumers designed for three-phase voltage. When connecting, additional devices will be required, and you also need to be prepared for a loss of power.
Usually, three phases are supplied to an apartment building, and only one phase comes to each apartment. At the same time, they try to distribute the load proportionally, excluding phase imbalance. It is also taken into account that the voltage of 220V is less dangerous than 380V, from safety measures.
If the consumer plans to connect to an electrical network with good power of more than ten kW, it is necessary to use a three-phase voltage.
The difference lies in a cable supply with four / five cores to the house or cottage. What is the difference between a two-wire connection? In this case, the consumer receives two voltage values: the linear voltage equals 380 V, and the phase voltage is – 220 V.
Measurement is made as follows. The phase voltage is measured between the neutral conductor and each phase alternately, and the linear voltage is measured between the phases.
We should bear in mind that there is no three-phase load in cottages where the installed power exceeds ten kilowatts. We must evenly distribute the active power between the phases.
It is the difference with a single-phase connection, and there is no need to distribute the power.
Why Powerful Equipment is Often Three-Phase
The main factor to use a three-phase connection to a powerful load is the transmission of high power with a smaller cable cross-section relative to a single-phase one. It significantly reduces the cost of electrical networks and switching devices.
Such a supply of electricity is used for industrial enterprises, workshops, farms. That is, for organizations where the primary consumers are three-phase electrical installations.
These can be electric motors, powerful drying units, stationary welding equipment, metalworking and woodworking machines, etc.
Advantages and Disadvantages
Each network, a single-phase and three-phase current system, has its advantages but not without its disadvantages.
Let’s consider the main advantages for the 220V line:
- They are uncomplicated. The scheme can be understood by a person with minimal knowledge of electrical engineering.
- Two wires are sufficient for connection (if grounding is not used). It dramatically simplifies the network.
- Relatively low hazardous voltage.
The main disadvantage is high currents with high power consumption. Therefore, a single-phase connection is practically not used for powerful devices (7-10 kilowatts or more). Now let’s consider how a 3-phase network differs from a 1-phase one.
For networks with a voltage of 380 V:
- The connected power is limited only by the cross-section of the conductors and the power allocated by the mains.
- We can use it to provide electricity to any facility.
- It is possible to “select” the phase with the best parameters for supplying critical single-phase consumers. For this, phase switches are used.
The disadvantages include:
- Expensive cables and switching equipment.
- Dangerous voltage.
Do Single-Phase Networks Meet in their Purest Form?
The energy system of our country is designed to use a three-phase network. All generators in power plants produce three phases. It applies to hydroelectric power plants, nuclear power plants, thermal, tidal, etc.
Such a scheme of power transmission over long distances is the most economical. To transmit the same power with a single-phase line, it will require large cross-section wires. Therefore, single-phase networks for the transmission of electricity are not used.
However, single-phase power grids are widely used as emergency power supplies. Gas or diesel power plants are used and installed at facilities where power outages are unacceptable. For example, to supply electricity to hospitals (intensive care units or operating rooms), telephone exchanges, emergency notification systems, etc. Three-phase diesel generators are used for power consumers.
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