Most home masters, at least in general terms, know the characteristics of the electrical network. However, there are those who do not even roughly guess what current is in the outlet, what is its voltage. This is actually not an idle question. Many people want to know which current is more dangerous for human health - alternating or constant, what are its strength and effect on the body. Today's article will answer all these questions.
What is alternating current: definition
Everyone has heard this term, but not everyone knows what it means. The variable is the chaotic movement of charged particles, changing its polarity from plus to minus with a certain frequency, which is measured in hertz (Hz). If you draw a graph, then this value will look like a sine wave, periodically intersecting the coordinate axis "X". If we talk about three-phase current, then it flows not in one conductor, but in three. The sinusoids of the phases are ideally completely identical, but are shifted in relation to each other by 120 degrees.
Alternating current is ubiquitous. It is produced in power plants by generators with various drives. Such a current is simple to transmit at different distances and it is quite easy to get a constant from it, which can not be said about reverse transformation. For "transportation" with the least loss, the voltage rises to 25 kV, as a result of which, according to the laws of physics, the current strength measured in amperes (A) decreases. When he reaches the desired point, he gets to the primary transformer substation. On it, the voltage drops to 6 kV and goes on. The last transformer still lowers the voltage to the usual 0.4 kV (400V). It is this current in three phases that enters the apartment buildings. Here, the phases are evenly distributed, as a result of which 1 phase is supplied to each home, capable of providing premises with an electrical voltage of 220 V.
So what is the current in the outlet? Of course, variable. Almost all household appliances work on it. If the device requires direct current, special transformers with rectifiers (diode bridges), which are called adapters, are used. Such power supplies are often equipped with televisions, computers, music centers.
DC Current: Features
His strength and direction are unchanged. Here, the conductors carry a certain charge - positive or negative. In everyday life, not only adapters are responsible for the generation of direct current. It can be obtained from batteries, galvanic cells. The DC voltage in households is small - usually from 1.5 V to 24 V.
In industry, it is used for engines with large inrush currents. This allows for smooth adjustment of the rotation speed. Here, direct current is generated by special generators that create eddy currents of the electromagnetic field.
What you should know about amperage and voltage
It is not enough to know whether the current in the outlet is alternating or constant. Many other factors need to be considered. Many people think that the higher his tension, the more dangerous he is. In fact, everything is quite the opposite. As already mentioned, with increasing voltage, the current decreases, and with damage, this parameter is dangerous for the body. But this statement is true only for a constant value. Alternating current does not have a certain strength - this parameter will depend on the load. The more devices connected to a 220 volt electrical outlet, the higher this value in the conductor. The limiter for increasing this parameter will be protective automation, which will not allow the current strength to increase to critical limits by turning off the power to the home network.
What current goes into the outlet: characteristics of household voltage
The standard voltage of a household network between phase and neutral is 220-240 V. The current strength depends on the number of consumers and their characteristics. Let's try to calculate the parameters when connecting a washing machine with a water heater, 2.5 kW. To find out what current strength in the outlet will be present when connecting such equipment, it is necessary to clarify some values. For calculations, you need a power factor. It is indicated in the technical documentation and on the nameplate of the device. If this indicator is absent, the value of 0.95 is taken as the calculation.
To find out the current strength that occurs when the heater is turned on, you need to multiply the voltage by the power factor, and then divide by the obtained value 2.5 kW that the washing machine consumes. The calculations will look as follows: 2500 W / (220 × 0.95) = 11.96 A. It turns out that the usual cheap 220 V electrical outlet is not suitable for such equipment - its maximum is 10 A. You will have to purchase a more expensive product that can withstand up to 16 A.
Protective automation: how it can save a life
By rewriting all the data of household appliances connected to a certain line, you can determine what current in household outlets is generated when all equipment is turned on at the same time. This will allow you to choose protective devices with suitable parameters. Many underestimate the role of RCDs in the power supply circuit, believing that a conventional circuit breaker is quite enough. However, these devices have completely different purposes.
The circuit breaker is designed for forced or emergency opening of the circuit in the event of an overload or short circuit. But he is not able to protect a person from electric shock in case of damage to the insulation of the current-carrying conductor and its contact with open parts of the body. But this work is successfully performed by the RCD. If the room is equipped with power outlets with grounding, then during a breakdown there is a current leak, which is fixed by the residual current device, instantly interrupting the supply of electricity. The problem with RCDs is that it does not respond to a short circuit, and as a result it can burn out. For this reason , the residual current circuit breaker is mounted in conjunction with a circuit breaker.
Mains voltage and its changes
It is clear that the question of how many amperes the current in the outlet is incorrect is a variable value. But why can the voltage in the network fall or increase sharply? The most common causes of these problems are two - a worn-out transformer at a substation that requires replacement and unskilled electricians who disconnected the phases before putting the house into operation. If with the first option everything is more or less clear, then the second is worth dwelling in more detail.
Causes of phase imbalance and its consequences for household appliances
If there are three apartments on the site, then the exclusion is as follows - a common zero for all rooms and one of three phases for each. At the same time, a riser is replaced on each floor. If in the first the third phase is connected to a two-room apartment, in the second it will go to a four-room apartment, even higher it will be a one-room food. This alternation allows you to evenly distribute the load. If you start up one phase in all four-room apartments of the entrance, and even imagine a cold winter with the need to use electric radiators, it is easy to understand how the network is overloaded. In this case, the line voltage may drop. Due to phase imbalance, an additional load will be applied to the transformer.
Now imagine that people returning from work (usually at the same time), it got warmer on the street, because in several apartments the radiators were turned off at once. The result is predictable - a power surge and a possible failure of household appliances. Often this happens in apartments with improperly selected automation and the absence of ground outlets.
Some tips for choosing RCD and AV outlets
The first step is to write down separately the power of all household appliances, dividing them into groups from which they will be powered. After calculating what current in the outlet will be maximum, you can determine the parameters of the circuit breaker and RCD, required for a particular line. If a common protective shutdown device is planned, then all current indicators are added up. This is quite acceptable, but it should be remembered that each group must have a separate circuit breaker. It is installed after the RCD, which is powered by an electricity meter. Here, between the meter and the residual current device , the installation of a common machine is necessary. It will protect the RCD in the event of a short circuit or heating of the wiring. Another place for the mandatory installation of a circuit breaker or batch switch is in front of the electric meter. It is used if necessary to replace or maintain the meter.
To summarize
Information on the question of what kind of current is in the outlet has become clear - alternating. Its value is not determined and depends only on the power consumption of household appliances included in the network. The voltage in the network is 220-240 V. A home master who does not deal with issues of electrical engineering professionally, these characteristics are quite enough. If you need to calculate the current strength in the home network at full load, you can always use the calculations presented in the article. This may be needed to select protective automation with the necessary parameters, as well as with a complete replacement of the wiring.