If you are using an inverter, you might have noticed that the output waveform is not a pure sine wave. Instead, it may be a modified or secure wave inverter. However, you can easily convert it into a pure sine wave inverter with some simple steps.
Firstly, you need to know how your inverter works. The two-volt DC from your battery is connected to a couple of MOSFETs, whose gates are connected to a PWM generator IC. The switching frequency in this case is 33 kilohertz. The voltage is then converted to 220 volts AC using a transformer and goes to the transformer inputs. The output voltage of this transformer is then connected to a bridge deal rectifier and a bit capacitor, which results in 260 volts DC. These four MOSFETs then switch by another PWM generator IC to convert the DC voltage back to AC voltage with a frequency of 50 Hertz.
To convert this secure inverter to a pure sine wave inverter, you need to solve the first problem which is the peak voltage. If you convert the inverter to pure sine without solving this problem, the output voltage will be 180 volts instead of 220 volts RMS. You can solve this problem by increasing the output voltage of the transformer. You can do this by either increasing the outputs or secondary winding turns number or decreasing the primary winding turns number.
After solving the peak voltage problem, you need to increase the switching frequency of the input MOSFETs from 33 kilohertz to 96 kilohertz. This is because you decreased the turning number of the primary and decreased the inductance. According to the data sheet of IC TL494, you will need to replace the 15 kilo ohm resistor to 4.7 kilo ohm resistor.
The next step is feeding an s PWM signal to the MOSFETs gates. To do this, you need to remove the IC from the board and connect the s PWM signals that come from an Arduino board in place of pin number 8 and pin number 10 of the IC. This will result in the output of the inverter having an s PWM.
To convert the s PWM to a pure sine-wave, you need to use a low-pass filter in the output. However, after connecting the low-pass filter, the waveform may not be clean and there may be some spikes. To fix this, you can put a 0.8-microfarad capacitor in the output and the output will become a clean pure sine wave.
Finally, you need to create a feedback loop by connecting the transformer to the feedback pin of the IC. This will make the output voltage stable whether the load is on or off.
In summary, there are five steps to convert any modified or secure wave inverter to pure sine-wave. These steps include increasing the output voltage of the transformer, increasing the frequency of output MOSFET switching, feeding an s PWM signal to the gates of the output MOSFETs, using a low-pass filter to convert the s PWM to pure sine-wave, and using a feedback loop to make the output voltage stable.
You can find the wiring and Arduino coding in the description of this video. By following these steps, you can easily convert your modified or secure wave inverter to a pure sine wave inverter.