What is the inverter working principle?

This article will introduce the inverter working principle from 3 phase inverter, DC to AC inverter, pure sine wave inverter.

1. 3-phase inverter working principle

A three-phase inverter is a device that converts direct current into three-phase alternating current. Here’s how it works:

Rectification stage: First, the DC power supply passes through a rectifier to convert the DC power into positive pulses with fixed amplitude. This usually involves the use of thyristors or diodes for rectification, ensuring that the DC current is in a consistent direction.

Intermediate Capacitor (optional): In some cases, the inverter may include an intermediate capacitor to smooth out fluctuations in DC power to reduce ripples in the output.

Inverter stage: The rectified DC power then enters the inverter, which uses switching devices (such as transistors or IGBTs) to convert the DC power into AC power. This involves splitting direct current into a series of pulses, simulating the waveform of three-phase alternating current.

PWM modulation: Modern three-phase inverters usually use pulse width modulation (PWM) technology to generate high-quality AC output waveforms by adjusting the frequency and duty cycle of the switches. PWM modulation provides more precise voltage and frequency control, producing a near-sinusoidal output.

Output stage: The output of the inverter passes through an output filter to smooth the output AC power and remove any high-frequency noise or harmonics. Finally, the generated three-phase AC power can be supplied to the grid or load.

Control system: The entire inverter system includes a control system that monitors the characteristics of the input DC power, adjusts the operating parameters of the inverter, and ensures that the output AC power meets predetermined standards in terms of voltage, frequency, and waveform. Control systems typically use microprocessors or digital signal processors to implement advanced control algorithms.

2. DC to AC inverter working principle

A DC to AC inverter is a device that converts DC power into AC power. Here’s how it works:

DC input: The starting point of the inverter is a DC power source, which can be a solar cell, battery or other DC energy source.

Inversion stage: DC input is inverted into AC power through the inverter’s electronic switching devices, such as transistors or MOSFETs. This involves splitting direct current into pulses, simulating sine waves or other shapes of alternating current.

PWM modulation: Modern DC-to-AC inverters often use PWM technology to generate high-quality AC output waveforms by adjusting the frequency and duty cycle of the switches.

Output stage: The inverter’s output is smoothed through an output filter to remove any possible high-frequency noise or harmonics. The output AC power can be used to drive AC motors, supply household electricity, or connect to the grid.

3. Pure sine wave inverter working principle

A pure sine wave inverter is an inverter that can produce a nearly ideal sine waveform. Here’s how it works:

Inversion stage: The DC input is inverted into a basic square wave through the inverter’s switching devices, such as transistors or IGBTs.

Harmonic filtering: By adding appropriate filters, the harmonic components in the square wave can be filtered out and gradually approach a sine wave.

PWM modulation (optional): Pure sine wave inverters may use PWM modulation technology to further optimize the output waveform by adjusting the frequency and duty cycle of the switch.

Output stage: The output AC power passes through the output filter to smooth the output waveform. The output of a pure sine wave inverter is very close to an ideal sine wave and is suitable for applications with high power quality requirements, such as precision equipment and some electric motors.

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