In this article we will cover what is a DC / AC power inverter, How do current inverters work? and what are the applications of voltage inverters ?. For this we need to understand the principle of transforming energy into AC voltage, through a 12 Vdc inverter with a transformation to 220 Vac.
What is a current / voltage inverter?
Voltage inverters or current converters have arisen for an increasing demand to use electrical equipment such as televisions and equipment for domestic use in cars or camps and also the use of these resources in areas where electricity is not available. Household appliances are available on the market with voltages between 127 v and 220 v, thus the need for the inverter or voltage converter to help in these conditions arose.
Current inverters are electrical equipment with specific electronic circuits capable of transforming DC energy from batteries into alternating electrical energy, usually at a voltage of 127V or 220V.
A widely used example is emergency lamps that, under the normal power supply, charge the 12 Vdc battery, but when there is a power outage, the lamp is energized through a converter circuit, which converts the 12Vdc to alternating from 110V or 220V, supplying power to the lamp.
How a current inverter works:
But how current converters work, look at the diagram below:
An inverter as shown in the block diagram above is formed by a circuit called a power oscillator, this power oscillator converts the DC voltage into a pulsating DC voltage, this same voltage is applied to a Trafo ( transformer ).
Converting the DC voltage into a pulsating voltage is necessary since transformers do not operate with a continuous voltage, it is necessary that voltages that fluctuate in time be applied so that the process of converting electric energy into magnetic flux takes place.
This conversion in turn generates currents induced in the secondary of the transformer. This phenomenon in alternating current is called electromagnetic induction.
The process generates an electromotive force in a coil traversed by a variable magnetic flux, this created force goes against the cause that originated it (source current). In other words, a variable magnetic force produces a variable electromotive force, so they cancel each other out. If we apply a continuous voltage to a transformer, this phenomenon does not occur, generating high currents in the secondary coil. The transformer is responsible, in turn, for raising the input DC voltage at alternating voltages at the output, which can be increased between 10 and 50 times the input voltage.
Oscillators are not always able to print a perfect sinusoidal voltage waveform, similar to the distribution network, they can generate dangerous voltage spikes to the equipment, being necessary to use the voltage regulator circuit to stabilize the output of the current inverter. After going through the voltage regulator circuit we have a perfect conversion performed, being able to take advantage of the alternating voltage.
Weakness of current inverters:
By the principle of energy conversion we have to observe that, as the block diagram demonstrates, we cannot create energy, only transform it. For example, we have a 24V battery as a source, with a maximum working current of 10A, so we have a total power of 240W.
Thus, if we disregard electrical losses, after carrying out 100% of energy conversion to a voltage of 220Vac, we have a total utilization current of 1.09 A. This working current provides us with exactly the same initial power as the DC source, proving that the energy is the same initial, being only transformed.
Look at the image below:
We can conclude that voltage converters generally do not support large loads, due to the principle of energy conservation, since the batteries do not have a large amount of power. This way, we can observe a disadvantage in the use of this equipment.
Inverters are divided into two broad categories:
Pure wave inverters
The waveform that pure wave inverters produce is a perfect sine wave, just like the energy supplied by the power grid. These inverters guarantee the correct functioning of the equipment connected to it. They are fundamental to supply refrigerators with compressor, motors and pumps in their majority. Some electronic equipment may not work well if the wave is not pure sine.
Modified wave inverters
The waveform that the modified wave inverters produce is not a round, progressive sine wave as in a normal sine wave, but a square or a ladder shape. Some equipment is not perfect, although resistive loads (heating, incandescent lamps, etc.) do not suffer from this type of modified waveform. However, the various electronic equipment may have their lifetime compromised, given the difficulty of their power supplies in converting this type of modified wave into the direct current they need to function.
For example, on televisions, it is common for a horizontal streak or interference to appear along the screen.
Applications for the current inverter:
They can be used to power common electrical appliances from batteries in boats, cars and camping tents. Current inverters can be used in places where conventional energy does not exist for the same purpose, batteries are often charged by solar panels during the day.
In emergency lighting systems for cinemas, shopping malls and companies, current converter systems for lamps are used, in the absence of mains voltage they are energized by converting the energy stored in batteries.
In rooms of server systems called CPDs where it is necessary for the computers to operate without ceasing, the servers remain energized, even without the availability of conventional voltage through the UPS, keeping the circuits energized until the power is restored. The autonomy time of the conversion carried out by the voltage inverter varies according to the available battery bank.
There are important applications for current inverters and we often use these resources in our daily lives without even realizing it. If you want to go even deeper into the topic of converting DC power to AC, we provide a frequency inverter measurement video .
I hope you have learned more about this important application as we increasingly use this conversion feature in electrical applications and day-to-day solutions.