A couple of years ago when Honda released first generators equipped with the inverter technology, I had the same question in my mind – what is an inverter generator?
What is the difference between a generator and a good inverter?
What is an inverter generator and how does it work?
An inverter generator is a unit which operates like this:
Step 1. The raw AC (alternate current) energy produced by the engine of the generator is converted to the DC (direct current) power.
Step 2. The built-in electronic inverter converts it again back to the AC power rated at the standard US rate of 120V and 60Hz.
Result: This kind of inverted AC power is much more stable than in the case of conventional generators. Since it is delivered in steady sine waves, it creates less harmonic distortion and can be safely used to power sensitive devices such as laptops or medical equipment.
The following graph explains the difference between the AC electricity delivered by conventional generators and the “cleaner” power provided by inverter generators.
As you can see in the case of the conventional generators the AC current is “unsteady”. These deviations from the regular sine wave are known as harmonic distortion. The total amount of these occurring while the generator’s engine is on is known as THD – Total Harmonic Distortion.
But is THD a big thing and a potential cause for worries when it comes to the safety of your electrical equipment? In fact – yes, it is.
How does THD affect the safety of your electric equipment?
Quite a lot of old school electrical appliances can handle higher levels of THD pretty well. All in all things like drills, electric saws and a lot of other electrical equipment used at work and home were designed in the times when the electricity grids were much less technologically sophisticated than today. Those appliances can generally work safely even with the relatively high total harmonic distortions.
By saying “high” we should define here what is defined as “clean energy” – the type of power which can be safely used also with more sensitive hi-tech electronics. Engineers generally agree on 3% THD as the maximum threshold for the power to be classified as clean.
Modern electric grid power in the US operates for the vast majority of time below this threshold. This is one of the reasons why you should probably never be afraid of charging your laptop via a wall socket. That is simply because you are nearly guaranteed that it won’t damage your electronics (although rare exceptions happen).