A Modified Sine Wave inverter is a type of inverter that has been modified to include a sinusoidal input. This type of inverter is used in some applications where the input signal is not a pure sine wave. A Modified Sine Wave inverter can be used to create an AC or DC power supply. A Pure Sine Wave inverter is a type of inverter that has been designed specifically for use with pure sine waves. A Pure Sine Wave inverter can be used to create an AC or DC power supply. A Pure Sine Wave inverter is also more expensive than a Modified Sine Wave inverter, but it offers better performance and reliability.
What Is an Inverter?
An inverter is a device that can take a Direct Current (DC) power source and convert it into Alternating Current (AC). AC power is what comes out of your wall sockets, so any device designed to plug into the wall expects AC power to function.
An inverter essentially does the opposite of what the power brick for your laptop or smartphone does. Electronic devices like PCs and consoles need DC electricity, so they convert AC power into that using a component known as a rectifier. This is important to remember after we’ve covered the main inverter types.
DC vs. AC Electricity
In case you don’t know the difference between AC and DC power, here’s an optional recap of the basics.
AC power is generated at power stations by devices called alternators. There’s one in your internal combustion car as well. An alternator is like an electrical motor but in reverse.
Using steam power, the alternator spins copper wire within a magnetic field. This causes electricity to flow. However, since the copper wire is spinning through both magnetic poles, the direction of the flow flips with each full rotation.
DC power, on the other hand, only flows in one direction. It never changes direction but flows from the negative terminal of a battery or other DC power source to the positive terminal.
As you can see in this diagram, when you plot out AC and DC current polarity, AC power forms a smooth wave. This is known as an AC sinusoidal or “sine” wave.
An inverter’s job is to reproduce that wave from a DC power source, and there are two answers to this problem.
Modified Sine Inverters Simulate AC Power
A modified sine wave inverter produces an approximation of a real AC sine wave. If you chart it out, it looks like a sine wave at first, but if you look closely, there are jagged stair steps in the waveform as the inverter crudely flips between polarities rather than the smooth wave seen above.
Devices designed to run from an AC power source will all generally run on a modified sine wave. However, they might not work correctly. AC electrical motors in particular shouldn’t be used with modified sine inverters. Since the curve of the wave isn’t smooth, the motor vibrates, builds up heat, and will have a shortened lifespan.
Devices without AC motors tend to work as expected with modified sine wave inverters, and any device with a rectifier cleans up that rough AC wave as it turns it into DC power. So lamps, TVs, and other devices are OK for modified inverter use. The major advantage of modified sine inverters is that they are less expensive than pure sine models.
Pure Sine Inverters Offer the Real Deal
Pure sine inverters are more sophisticated devices that can exactly replicate an AC sine wave from a DC power source. Because of their added complexity, they’ve historically cost a lot more than modified sine inverters. However, their cost has decreased dramatically, making it harder to choose which type is right for you.
If you have to run any AC motors, then a pure sine wave system is required. If you want to run your electronics with perfect reliability, a pure sine inverter is highly-recommended. If you never want to worry about whether something will work on your inverter, pure since is the way to go.
Do You Need AC Output?
Remember when we said that lots of your appliances and devices have a power supply that converts AC power into DC power? Well, that conversion isn’t free. Converting from one type of current to the other results in a small but not insignificant power loss as heat. When you plug an AC to DC power brick into an inverter, you go from DC to AC and back to DC again.
This is quite wasteful, so if you have any other choice, it would be best to have a DC to DC power transfer. Many modern inverters, modified or pure sine, offer direct DC output. This can be in the form of USB ports or as barrel-plug DC output like the one that plugs into your laptop. If you can, make use of these and the inverter turns your batteries into one huge power bank.
