Understanding Energy Sources: What is an AC Current & How is it Different From a DC Current?

When working with large-scale lighting, lighting experts need to consider multiple factors to find the right lighting solution for the job. Some of these variables are fairly obvious, like brightness, placement, and lamp temperature. Other solutions require a more nuanced approach.

In parking garages, for example, brightness is one of the most important criteria of effective lighting. But running bright LEDs continuously for a 24 hour period can skyrocket energy costs. That’s why Imperial Lighting made the decision to install multi-level sensors in addition to energy-saving LEDs in a municipal parking garage in the Chicago-area.

Placing bright LEDs on a sensor is just one example of taking the nuanced approach with lighting, but there are many other factors experts can weigh to achieve  energy efficiency and savings. And that includes considering the right energy source to power that lighting system.

What is an AC Current?

AC, or alternating current, is an electric current that alternates direction to continuously change its output. Alternating currents generate high voltages which make them a great option for lighting systems that span long distances — think delivering power to homes on a power grid or powering transformers.

Alternating currents are considered a sinusoidal waveform. The current begins at zero and slowly reaches the top of the sinusoidal peak, above the x-axis. The flow then reverses, returning to zero, and reaches its maximum level below the x-axis. This pattern is referred to as frequency.

Due to its long-range transmission, alternating currents are able to make up for energy losses on a large scale. It’s also cheaper to change the voltage amount of ACs than DCs. But direct currents offer their own unique advantages that ACs do not.

What is a DC Current?

Where alternating currents flow in more than one direction, a direct current, or DC, puts out energy in one, consistent direction. When you flick on a flashlight or start your car, you are experiencing the power output of a direct current. Because the power travels in one consistent direction, this type of current is able to flow through conductors, semiconductors and insulators.

What is the Difference Between AC & DC Current?

The difference between AC and DC current is actually very simple. As we stated, ACs alternate the flow of energy output while DCs send direct energy. ACs tend to be higher voltage and lower current while DCs are lower voltage with the ability to travel at high capacity for short distances.

Another striking difference between AC and DC current is that a direct current travels through conductive material, like the center of a wire, while an alternating current travels just under the surface. This is due to the wave-like pattern of an alternating current and it results in a phenomenon called AC resistance which is a measure of energy loss.

Alternating currents have a higher rate of energy loss than direct currents. This is largely due to the way an alternative current’s energy field is constantly growing and expanding through the sinusoidal cycle. On a small scale, AC resistance can cause greater energy loss relative to its output, but generally, the energy loss amount of an AC current is not as noticeable on a large scale.

How is AC Power Converted to DC Power?

When an AC current flows through a transformer it is converted to DC power through transformer action. Transformer action uses electromagnetic induction to create an electromagnetic field that converts an AC signal at the primary coil into DC voltage in the secondary coil. This transformation relies on the ratio of turns between the first and the second coil and is called the turns ratio.

Transformers can either increase or decrease the amount of voltage it puts out by the number of turns in the secondary coils. For instance, if the secondary coil has more turns than the primary, the primary voltage will be lower. When secondary coils have fewer turns than the primary, this will create a decrease in voltage. This is called a step down transformer.

What Devices Use AC Vs DC Currents and Vice Versa?

Lamps, refrigerators, TVs, and other electrical devices that plug into an outlet run on DC power. Additionally, when it comes to AC vs DC currents, small electrical devices like a cellphone are powered by direct currents.

It sounds contradictory that a majority of household items run on direct power when power grids use AC. However, transformers run on alternating current. On the power grid, transformers convert the long-range alternating current into the direct current that powers lighting systems, electronics, and home appliances.

In the AC vs DC current debate, experts question whether a direct current could be used to power homes and businesses as opposed to an alternating current. One possible solution is a DC microgrid. In this scenario, small, local grids generating direct power would provide energy to solar panels and wind turbines that would then power homes and commercial buildings in the area.

Microgrids offer a more sustainable energy option than power plants that run on fossil fuels but as the vast majority of our nation’s energy supply comes from an AC power grid, there are smaller adjustments business owners and homeowners can make to reduce overhead costs from energy and create more eco-friendly energy use.

Can LEDs Run on AC Power?

One of the easiest ways to increase energy efficient practices is to upgrade building and facility lighting to LEDs and invest in an energy management solution. With utility monitoring and energy efficient lighting, business owners can take control of their energy use and discover various ways to improve its efficiency.

Because LEDs run on direct current, when linear strip-lighting stretches beyond 100m, “DC drivers suffer from losses over distances”, according to LEDs Magazine. The way to get around this limitation is higher voltage drivers at the start of the circuit and regulators at the end. Regulators, however, can waste power. This is where an AC current can help in large-scale LED installations.

Modern LEDs have a transformer between the fixture and the wall socket that convert AC into DC power. DC bridge circuits also offer a similar solution, converting AC power into DC, this option however, requires a higher voltage driver. There is also an AC-LED system in which lamps are placed on a series so that the “voltage drop across the whole string equals the supply voltage”.

Whether a series of LEDs get their power from a traditional DC source, or large-scale LEDs around a building’s exterior are configured to run on an AC current, LEDs still offer facilities and business owners the greatest opportunity for energy savings. Contact the lighting experts at Imperial Lighting today and discover where you can save on utilities, lighting, and building energy management costs.