DC/AC power inverter represents a piece of equipment used to convert DC Power (Direct Current ) to AC Power (alternating current). But before we get to its operating principle, let us first clarify how DC and AC differ.
DC and AC power: what is the difference?
DC refers to electrical power with charges flowing in one direction. This happens because of two poles – positive and negative - with the electric potential difference, more commonly known as voltage. It is the force that pushes free particles through a closed circuit, which creates a direct current.
Alternating current represents the type of electric power where the flow of charge periodically changes its magnitude and direction. This current is produced using an AC generator, where the potential between two terminals switches in a fixed time interval, forcing the electrons to move back and forth at a regular frequency.
DC power runs most portable appliances using batteries such as phones and laptops, DC-based lighting (LED), and car batteries. And, of course, DC power is the power solar panels generate.
The most important application of AC is power transmission. It is cheaper to produce and easier to step up and down in voltage with transformers. As our homes most commonly receive power from the public grid, most of our home appliances are designed to receive AC power.
Working principle of a power inverter
We might need to convert DC to AC, for example, to draw power from a battery and use it to run all kinds of devices, such as TVs or kitchen appliances. Power inverters are used for exactly that purpose. Here's a quick glimpse at how they work.
As DC flows continuously in one direction, it can be thought of as a straight line, while AC flows in the shape of a sine wave going up and down at regular intervals. To turn the linear DC into a wave, most inverters use Pulse Width Modulation (PWM) technology. Basically, PWM switches the voltage on and off with specific pulses. The width of these pulses is configured in such a manner that the current gradually takes a form similar to that of an AC sine wave.
What are the three types of power inverters?
Power inverters fall into three types: sine wave inverters (sometimes called pure sine wave inverters), modified sine wave inverters, and square wave inverters.
- Pure sine wave inverters produce an almost perfect copy of the original alternating current. That is why they’re perfect for sensitive equipment and electronics requiring clean AC power to run smoothly.
- Modified sine wave inverters offer a cheaper but less efficient alternative. In these inverters, the polarity reverses from positive to negative less smoothly, giving the wave a stair-step, square pattern. They can be used to power simpler devices such as lights and old TVs.
- Square wave inverters represent the oldest and simplest type that generates abrupt square pulses. These options have proven much less reliable and can potentially damage the devices.