How Does A Pure Sine Wave Inverter Work?

If you’re a fan of camping or extensive road travel, but also enjoy modern conveniences that run on electricity, a pure sine wave inverter may be your new best friend. Sine wave inverters are devices that transform power from a battery into the same type of power you get from a typical wall outlet in your home or office.

Specifically, sine wave inverters transform direct current (DC) from a battery into an alternating current (AC). The AC power can then be used to run appliances, lamps and light strips, compressors and other devices that cannot run directly on battery power.

The concept of a sine wave inverter is relatively straightforward, but things can get a bit more complicated when you start to browse through all the different sine wave inverters out there. You’ll find two main types of inverters: pure sine wave inverters and modified sine wave inverters. Once you know the differences between the two, you’ll know the right inverter to choose.

What is the Sine Wave Inverter?

Let’s start by understanding what a pure sine wave inverter is and why you would need one for your electrical system.

By now, you might already know that there are two types of current:

• AC, for Alternating Current
• DC, for Direct Current

What Is The Difference Between AC vs DC?

Brief History

When the world started its electric revolution (end of the 19th century, beginning of 20th), two famous scientists tried to establish their technology as a standard.

On the one hand, Nikola Tesla was pushing for the adoption of AC electricity and Thomas Edison strongly defended DC electricity. Obviously, Tesla won the battle as nowadays AC is the main electric current for all common household appliances and electric motors.

However, DC is still used and regained interest recently with the development of solar energy. Indeed, solar panels are producing DC power, and so are batteries.

Now that some historical context has been provided, you may still be wondering what the main differences between AC and DC are?

First of all, electricity is a flow of electrons.

With DC, electrons flow in one way, from the negative electrode to the positive electrode. It can be represented by a straight and continuous current over time.

On the other hand, with AC, electrons flow alternatively in both ways in a periodic cycle. It can be pictured as a sine-wave current over time.

Now that you understand AC and DC are different in their nature, it is recommended that you do not ever connect an AC appliance to a DC power source, it will be irreversibly damaged.

How Do We Convert DC Into AC?

To overcome the compatibility problem between DC and AC, electrical engineers created a device that converts DC into AC, and alternatively AC into DC if needed – this is whats known as the inverter.  

A pure sine wave inverter, will, therefore:

• Produce alternating current (AC) from a direct current (DC) source.
• Deliver high quality electric current similar to utility standards (voltage: 230V, frequency: 50/60hz).

In addition, pure sine wave inverters are also transformers. They raise the input DC voltage to a much higher AC voltage – e.g., 12V to 230V.

How Does A Pure Sine Wave Inverter Work?

Previously, we saw that pure sine wave inverters first convert DC into AC, and then increase the input voltage (12V, 24V, 48V…) to reach an output voltage of 230V (transformer), usable by all our household appliances.

Let’s detail those two steps performed by a pure sine wave inverter.

From Direct Current (DC) To Pure Sine Wave Alternating Current (AC)

In this section, a simple working principle that illustrates how pure sine wave inverters work will be provided:

The challenge is to turn a straight line (DC) into a wave (AC) in which the current flows periodically in both directions.

Let’s start with a simple switch.

Switching the DC current periodically will give you a squared shape current alternating between zero (switch Off) and maximum value (switch On).

Ok, now you have a periodical current but not flowing in both directions and still very far from a sine waveform.

To make the current flow in both directions, you would need a kind of automated switch that will alternatively flip the incoming direct current back and forth by reversing the contact.

This can be illustrated as a rotating disk with criss-cross connections. The speed of the rotating disk will determine the frequency of the alternating current.  

Now, you have a periodical current flowing in both directions. However, it is still the shape of a square. It takes a bit more electronic circuits to smoothen the square into a nicely defined sine wave.

How Do Pure Sine Wave Inverters Increase Voltage?

The second step is to increase the voltage of the pure sine wave current. DC is usually 12V, 24V or 48V. Whereas AC is 230V.

The transformer will do the job. It is an electromagnetic device, made of an iron core wrapped with two coils of copper wire: the primary and secondary coil. The low voltage current enters through the primary coil and the high voltage current exits out of the secondary coil.

Schematic representation of a transformer from 12V to 230V

In the end, the two coils are not in contact and the current is transferred from one to another via electromagnetic induction.

The wiring density of the two coils controls the output voltage. In a step-up transformer (increasing the voltage) the secondary coil has a higher wiring density than the primary one.

Transformers are everywhere, for example, your cell phone and laptop chargers are step-down transformers.

When You Need a Pure Sine Wave Inverter?

Pure sine wave inverters are typically the most expensive of the bunch. That’s because they produce AC power that most closely matches an actual sine wave, or the power provided by wall outlets. A pure sine wave is a steady, continuous wave that provides a smooth, periodic oscillation.

Pure sine wave inverters are at the top of the list of functionality, with the ability to run any and all equipment designed to work on a pure sign wave. All devices you power with a pure sine wave inverter will work to their full specifications. Another note is that certain devices will only work with pure sine wave inverters, and there’s a risk of damage, malfunction or not functioning at all if you try to run them with other types of sine wave inverters.

Devices that require pure sine wave inverters include:

• Appliances with AC motors, such as refrigerators, compressors or microwaves
• Other devices, like bread makers, certain battery chargers and light dimmers
• Audio and video equipment, satellite systems
• Certain medical equipment, such as many CPAP devices for sleep apnea and oxygen concentrators

Pure sine wave inverters cover all bases, ensuring everything you power with it will be running to its full functionality and capacity.

What Size Pure Sine Wave Inverter Should I Buy?

Pure sine wave inverters come in many sizes and power outputs to satisfy all needs.

Let’s first consider a car pure sine wave inverter:

Car Inverter – Max 1500 Watts

Many pure sine wave inverter models offer a cigarette socket to connect directly into your car. The source of energy will come from the car battery or from the car alternator.

In this configuration, your maximum inverter wattage should be 1500 Watts. There is no need for you to get a more powerful inverter, simply. Because your car alternator cannot produce enough power.

A typical car alternator produces between 40 Amps and 120 Amps at 12V. Therefore, maximum power of 480 W to 1440 W.

Don’t worry, 1500 W of power is already huge and you can run many appliances and electronic devices at the same time with this size inverter.

Solar inverter 1000 – 10kW

Pure sine wave inverters are widely used in solar off-grid and grid-connected systems. Usually, the inverter is connected to a solar charge controller (regulating the power of the solar panels) and to an energy storage system (Powerwall) or a lithium battery bank.  Some solar inverter models also have a built-in solar charger.

There is virtually no power limit for a solar inverter. However, most solar inverters range from 1000W to 10kW.

However, the rule of thumb would be to get an inverter as powerful as your solar panel array. For example, if you have 3kW of solar panels then you could get a 3kW inverter.

As the solar system can be easily upgraded. It is recommended that you get an inverter slightly more powerful than your solar panels.

Picking Equipment to Match Your Application

If you find yourself planning on the inverter being hooked up to public power, a generator or another power source and acting as a back-up source, you want a pure sine inverter charger. They have a built-in charger that will store power in a battery bank automatically when connected to outside power. With a transfer switch included as well that seamlessly transitions from external power to the inverter’s stored power. These are an excellent fit for mobile uses such as in a car, boat, RV and more.

Choosing the best sine wave inverter for you depends on its intended use. Review the variety of equipment you expect to run with the inverter, along with any specific manufacturer instructions that outline the type of inverter that works best. You can then move forward with confidence to select the optimum inverter for your needs. You can also shop with confidence when you shop for sine wave inverters at The Inverter Store.

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