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.
KATKO’s terminal series updated. Class A terminals available from 1.5 mm² to 300 mm².
KATKO’s terminals for aluminium and copper cables covers now terminals up to 300 mm2. 1.5-16 mm2 has also been updated and the whole range has been tested and certified according to EN 61238-1 Class A. Terminals also conform to EN 60947-7-1. Class A terminals are suitable for equipment and general use as feed-in terminals…
KATKO Oy has moved Katko Oy has moved to new premises on 18.11.2019. The new premises are located in Konala industrial area in Helsinki, close to the old Vantaa factory. “The increased capacity in the new premises allow us to better respond to our growing customer demand. Also, it was important for us as an…
Katko’s change-over switches – with or without an enclosure, 16-160 A & 630-800 A
Change-over switches, or transfer switches, are used when power source needs to be transferred, for example for the duration of maintenance work. The advantage of a change-over switch is that the user can easily switch the source of power. The mechanism of the switch makes sure that when main power is switched off, the alternative…