A mains inverter works by converting a DC (Direct Current) voltage into an AC (Alternating Current) voltage, matching the frequency and voltage characteristics of the mains electricity supply. It essentially mimics the power coming from your wall outlet.
Here's a breakdown of the process:
1. DC Power Source:
The inverter starts with a DC power source. This can be a battery, solar panel, or any other DC voltage source.
2. Inversion Stage:
This is the core of the inverter. It uses electronic switches (typically transistors like MOSFETs or IGBTs) to rapidly switch the DC voltage on and off. These switches are controlled by a circuit that determines the output frequency (e.g., 50 Hz or 60 Hz).
- Switching: The switches flip the polarity of the DC voltage back and forth. This creates a square wave AC voltage.
3. Waveform Shaping (Optional but Common):
The raw square wave output isn't ideal for most appliances. Therefore, inverters often include circuitry to shape the waveform into a smoother approximation of a sine wave.
- Modified Sine Wave Inverters: These are simpler and cheaper. They produce a stepped waveform that's closer to a sine wave than a square wave. Many appliances work fine with this, but some sensitive electronics may not.
- Pure Sine Wave Inverters: These are more sophisticated and produce a waveform very close to a true sine wave. They are suitable for all types of appliances, including sensitive electronics. They often use techniques like Pulse Width Modulation (PWM) to create the sine wave. PWM involves varying the width of the pulses to create a smooth sine wave output.
4. Voltage Regulation and Stepping Up:
The voltage from the inversion stage may not be at the desired level for the mains supply (e.g., 120V or 230V).
- Transformer: A transformer is used to step up the voltage to the required level. The transformer also provides galvanic isolation, separating the DC input from the AC output for safety.
- Voltage Regulation: Circuitry is included to regulate the output voltage, ensuring it remains stable even as the DC input voltage or the load changes.
5. Filtering:
Filters are used to remove any unwanted harmonics or noise from the AC output, resulting in a cleaner power signal. This usually involves inductors and capacitors.
Summary:
In essence, a mains inverter takes DC power, rapidly switches it to create AC, shapes the waveform to approximate a sine wave, steps up the voltage to mains levels, and filters the output to provide clean, stable AC power. The key is the controlled switching and shaping of the waveform to match the characteristics of the mains supply.
