What is the functioning of the solar inverter?

After learning the basic concepts and the functioning of the solar panels and the solar charge controllers, now it is the time to understand the functioning of the inverter, the other important component in your solar power system.

This conversion from direct current to the alternating current is done by the inverter.

As you know that the electricity produced or provided by the solar panels are DC (Direct current) in nature and most of our home appliances run on AC (Alternating current) current. There should be an interface which can convert the direct current from the solar panels into the alternating current to run our home appliances like fans, tube lights, fridges and televisions etc.

(1) Types of current

First of all, let us understand the basic difference between these two types of current. The direct current has the constant value of current while the value of current in case of the alternating current keeps on changing or it alternates between the maximum value and the minimum value with respect to time.

(2) The components of the inverter

The basic inverter consists of the following parts:

• Oscillator
• Amplifier
• Transformer (consists of primary and the secondary coil)

(3) Functioning of the inverter

Basically, an inverter does three main activities:

• It converts direct current into an alternating current through an oscillator
• It amplifies the alternating current through the amplifier.
• The transformer step ups the voltage to the desired level, which is 220 volts ac for Indian homes.

Let us understand with an example:
Take a magnet and a coil, and start rotating magnet near the coil, a current will be generated in the coil, the reason is that the varying magnetic field with respect to the time will induce the current in the coil. When one pole of the magnet reaches closest to the coil the current induced in the coil will have the maximum value and it will keep on deceasing as the magnet starts going away from it. Also, when the opposite pole starts reaching close, the current in the coil will change its direction. When this process is repeated, an alternating current is induced or produced in the coil. This alternating current produces its own magnetic field. No current will be induced when the magnet is static.
So, we need a changing magnetic field to induce alternating current in the coil.
Can an alternating current in one coil produce or induce an alternating current in other coil, placed near to it?
Yes, the alternating current in one coil will generate varying magnetic field, and the coil which is placed near to it will come under the influence of the varying magnetic field and the current will be induced in it. 

(i) Function of an oscillator:

• When you connect solar panel to the primary coil through an ON/OFF switch and put the switch ON, the direct current which has the constant value will start flowing in the primary coil. As the current is static in nature, no varying magnetic field will be generated and hence no current will be induced in the secondary coil. Therefore, we do not receive any output. Now, frequently connect and disconnect the circuit using the ON/OFF switch, this will generate a current which is changing with respect to the time and this alternating current will generate a varying magnetic field which will further induce the alternating current in the secondary coil. In this case, we receive output from the secondary coil. This switching function is performed by the oscillator.

(ii) Function of an amplifier:

• Actually, the output current of the oscillator is low and it needs to be amplified before feeding it to the primary coil of the transformer and this function is performed by the amplifier, it amplifies the current to the desired level.

(iii) Function of a transformer:

• The transformer consists of two coils one is called the primary coil and the other is called the secondary coil. The voltage supply in Indian homes is 220 volts ac. The basic function of the transformer is to either step up or step down the ac voltage. This can be achieved by increasing or decreasing the turns of the secondary coil. By doubling the turns of the secondary coil with respect to the primary coil you can double the output voltage. Actually, it does not increase or decrease anything, the input power to the primary coil and the output power to the secondary coil remains the same. It just converts low voltage and high current into high voltage and low current or vice-versa.

The direct current from the panel goes to the oscillator which converts it into alternating current. This current is further amplified by amplifier and in the last, the transformer step ups the voltage to the desired level. So, from here we get an idea about the importance and the basic functioning of the inverter.

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