A single-phase full bridge inverter is a type of power electronic circuit that converts direct current (DC) power to alternating current (AC) power. It is one of the most common and versatile inverter topologies, and it is used in a wide variety of applications, including motor control, power supplies,
The circuit diagram of a single-phase full bridge inverter is depicted below:
The power circuit of a single-phase full bridge inverter is quite straightforward. It consists of four components: four thyristors labeled T1 to T4, four diodes labeled D1 to D4, and a two-wire DC power source labeled Vs. Each diode is connected in a way that opposes its respective thyristor’s operation, for instance, D1 opposes T1, and so on. You can see this configuration in the figure below, which depicts the power circuit diagram of the single-phase full bridge inverter.
In the diagram, we’ve omitted the specific components responsible for turning the thyristors on and off to keep things simple. For our explanation, we’ll assume that each thyristor only conducts when its gate signal is active, and as soon as the gate signal is removed, the thyristor turns off.
Single-phase full bridge inverter Working Principle
The working principle of a single-phase full bridge inverter is based on the sequential triggering of thyristors that are positioned diagonally opposite to each other. In other words, for half of the time, thyristors T3 and T4 will be triggered, while for the remaining half, T1 and T2 will be triggered. This means that at any given moment, only two thyristors are active for half of the time.
Pay close attention to the gating signal waveform. You’ll notice that thyristors T1 and T2 are triggered simultaneously for a duration of T/2. During this period, the load is connected to the source through T1 and T2, resulting in the load voltage being equal to the source voltage with a positive polarity. This explains why the load voltage appears as positive and equal to Vs in the output voltage waveform.
Once the gate signals (ig1 and ig2) are removed, T1 and T2 are turned off. However, at the same instant, gate signals (ig3 and ig4) are applied, causing T3 and T4 to turn on. When T3 and T4 are conducting, the load is again connected to the source, and the load voltage magnitude is Vs, but with a reverse polarity. This reversal of polarity is the reason why the output voltage is depicted as negative in the voltage waveform.
Applications of Single-Phase Full Bridge Inverters
Single-phase full bridge inverters have a wide range of applications, including:
- AC Motor Control: They are used in variable-speed drives to control the speed of AC motors.
- Uninterruptible Power Supplies (UPS): They provide backup power to critical loads in case of power outages.
- Induction Heating: They are used to generate high-frequency currents for induction heating applications.
- Photovoltaic (PV) Inverters: They convert DC power generated by solar panels into AC power for grid integration.
- Laboratory Applications: They are used in various laboratory settings to generate controlled AC waveforms for research and testing purposes.
Advantages of Single-Phase Full Bridge Inverters
Single-phase full bridge inverters offer several advantages, making them a popular choice for various applications:
- Simplicity: The circuit topology is relatively simple, making it easy to understand and implement.
- Efficiency: They operate with high efficiency, minimizing power losses.
- Versatility: They can be used with a variety of load types, including resistive, inductive, and capacitive loads.
- Controllability: The output waveform can be precisely controlled using PWM techniques.
- Reliability: They are robust and reliable devices, capable of operating in harsh environments.