The Design And Construction Of 2kva Inverter

3.2 METHODOLOGY
3.2.1 STAGES INVOLVED IN THE PROJECT
These various stages are involved in the design and construction of a 2KVA inverter:
i.    Power supply unit
ii.    Multi-vibration unit
iii.    Frequency counter
iv.    Power amplifying stage/inverting stage
v.    Transformation stage
vi.    Filtering unit  
3.2.2 DESCRIPTION OF VARIOUS STAGE IN THE INVERTER POWER UNIT:
This unit consist of a power source that is obtained from a DC battery or cell. The power associated with any circuit can be divided from the multiplication of total voltage across the circuit and the total current flowing through the circuit. The power unit consist of a capacitor for smoothing the output. Thus the 12volts DC from cell battery. Which has been inverted to 12volts AC pulsating signal is now transformed to a higher AC voltage of 220volts rating. The rating of the transformer is 2000VA of 220volts with a constant frequency of 50Hz.

3.2.3  POWER AMPLIFYING STAGE OR INVERTING STAGE
This stage consist of power transistor that is connected in darlington pair. The transistor involved are the 1RN 250N of FET type. The drains of the transistors the output from the multivibrator drives the gates.
The mode of connection employed to connect the bank transistor in common source configuration in which the source leads of the entire power transistors in each half section of the transistor bank are connected in the common input of the transformer with respect to the ground.
Therefore, each section of the transistor banks conducts current in the opposite direction as a result of their alternating magnetic flux which links to the primary winding of transformer. (http://www.Sulekha.com/types of inverter/html).
3.2.4 MULTI-VIBRATOR         
This is also known as oscillator stage. The oscillator generates the pulse needed to drive the MOSFET. The unit is made up of an integrated circuit SG3524. The IC SG3524 in the oscillator generates 100Hz frequency but the required frequency needed to drive the MOSFET is 50Hz frequency.
This is obtained by; F/2 =100/2
                    = 50Hz
Where f = frequency
The oscillator generate 5V with a frequency of 50Hz trigger the two banks of the MOSFETs.
Also, the IC SG3524 is capable of operating in either mono-stable or Astable mode. It required an external capacitor (between pin 1 and 3) and an external resistor (between pin 2 and 3) to determine the output pulse width in the mono-stable mode and output frequency in the Astable mode.
Astable operation is enable by high level on the Astable output. The output frequency (at 50% duty cycle) at Q and Q output is determined by the timing component. Astable mode is what is needed in this project. (http://www.tahmidmc.blogspot.ng/2013/01/using-SG3524-pum-controller-explaination.html).
The connection and block diagram of IC SG3524NP is show below.