About Alternating Current

What Is Alternating Current?

Alternating current, for short AC, is the type of current that change (periodic) its direction and amplitute at certain time. Alternating current can be waves such as triangle, square, sine but sine waves are generally used.

History

Alternating current which is actively used today, in 1886 was produced in lab by Nikola Tesla. The first power plant to produce AC electric current was built in 1893 at the Mill Creek hydroelectric power plant in California. The founder of the hydroelectric power plant was Almirian Decker. Alternating current, which is used in many areas today, is still being developed.

How Is It Produced?

Alternating current is produced by alternators.

The alternator is a special electric generator that converts mechanical energy into electrical energy. An alternator uses a rotating magnetic field to do this work. In a generator, magnets called rotors spin in stationary conductor coils called stators, which are wound on iron. When mechanical energy spins the rotors, the magnetic field around the conductors changes and an electric current is generated.

Where is it used?

Alternating current is used in homes, street lighting and industry. During the transmission of electricity, high voltage is used to reduce the voltage drop in transmission lines. High voltage can also be obtained through transformers. The use of alternating current in transmission is to minimize loss. High voltage is reduced by transformers on the way to our homes. This allows electronic devices in homes to be used. While some devices work with the city network, tools such as telephones and computer chargers convert alternating current into direct current and reduce, for example, 220 volts to 6 volts.

So why was there a need for alternating current (AC) when there was direct current (DC)?

1. Alternating current is a system in which transmission at high voltage levels and consumption at low voltage levels are easier. In this way, the transportation of energy in transmission lines at low current and high voltage allows energy losses to be reduced and thinner and lighter transmission lines to be used. In other words, alternating current is preferred to minimize energy losses caused by low current. In this way, AC-based systems provide more efficient energy distribution while reducing the size and cost of transformers.

2. Alternating current is easier to generate than direct current. For example, generators generate alternating current when converting mechanical energy into electrical energy, making it much easier to generate electricity than direct current.

3. Alternating current is also used in the operation of remote control and automation systems. It is preferred in low-voltage circuits used for the transmission of signals and control signals. In this way, AC makes transmission and sensing more convenient in applications such as remote control devices, security systems, automation and control mechanisms.

Transformers

Transformers are electrical machines that allow the current or voltage value in an alternating current circuit to be changed as desired. In this way, energy is transferred from one circuit to another using magnetic coils. As the current passes through the conductor, it loses some of its electrical energy as heat energy due to resistance. Transformers aim to minimize this heat loss. For example, thousands of kilowatts of alternating current produced in dams are delivered to houses many kilometers away with minimal loss thanks to transformers. Transformers minimize heat loss by increasing the voltage as the current passes through the conductor.

The logic of transformers is electromagnetic induction. The variable current passing through the helix wrapped around a ferromagnetic core produces a variable magnetic flux in the core. This variable flux generates an electromotive force that varies along the other helices wrapped around the core. In this way, electrical energy can be transferred without any connection between the coils.

There are two types of transformers.

1) İdeal Transformers

In ideal transformers, efficiency is accepted as 100%. There is no core loss and it has infinite permeability. The current generated in the primary helix tries to create magnetic flux. Thus, current is generated in the secondary helix. This current is equal and opposite to the primary helical current according to Lenz’s law.

In ideal transformers the following equality is satisfied:

Vp/Vs=Np/Ns=Is/Ip

As can be seen from this equation, while voltage and number of turns are proportional, current is inversely proportional to these two variables.

2) Non-Ideal Transformer

The non-ideal transformer differs from the ideal transformer in the following ways:

· The energy efficiency of the ideal transformer is 100%. So, the output power is equal to the input power. Non-ideal transformers have various losses.

· In non-ideal transformers there is loss of magnetic flux, so inductance is limited and frequency is also limited.

· In non-ideal transformers, iron and copper losses are observed along with the resistances of the ferromagnetic core and helices.

So ideal transformers are used in mathematical analysis and to understand the operating logic of basic transformers, while in reality non-ideal transformers are used.