Alternating current (AC) and direct current (DC) are used side-by-side nowadays and both have attributes that make them valuable for certain situations. Nevertheless, modern history of electricity started with an existential war (the war of the currents) between AC and DC, with parties of each side trying to discredit one another. AC’s superiority of transmission and DC’s better ability to power electric motors were arguments that set the tone of early rivalry. While these qualities mattered, it was safety that raised most concerns for the public. 1
This day, after almost 150 years, safety is still the number one concern. Due to the varying nature of AC and DC different techniques must be used to safely disconnect the current. AC’s “zero crossing” interrupts current flow and is therefore relatively easy to break. DC, on the other hand, has no such characteristic and thus the arc tends to be longer and requires special blow-out coils or magnets to stretch and break the current. It is essential to use a right solution, and special attention should be focused on systems that operate with both currents, such as photovoltaics. 2
Difference between AC and DC
Past few decades have seen the rise of residential solar power systems and a drop in panel prices and increase in productivity has led to installation of smaller systems. This means that many owners of domestic PV systems choose to do some of the maintenance work by themselves. While it is okay to do some of the maintenance without having an electrician’s qualifications, it is only safe if the system has been properly installed and has separate isolators for the panels and the inverter – DC for the panels and AC for the inverter.
We strongly courage people to install solar power systems whenever it’s possible. It is a reliable source of power and can save a lot of money in the long term. Just remember that safe isolation of current before maintenance can only be accomplished with a switch that’s designed for the situation – whether it’s AC or DC.
Below, a video explaining different characteristics of breaking load in AC and DC.
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