Going ‘green’ is an ideal concept that is fast becoming a necessity, rather than a preferred option. In the global construction industry, there is an increasing drive to find means to integrate ‘green’ practices into building services. One of the prime areas where this can occur is in the field of building power consumption. In addition to using various alternative power sources, the efficient functioning of electronic appliances is critical. The extent of efficiency in electronic appliance functioning is further dependent on power quality, which is improved by power factor correction. With precise electrical design services, specifically electrical drafting services, and the use of active harmonic filters, smart MEP (M&E) engineering design for building services can contribute to the longevity of electronic equipment, resulting in decreased power consumption and reduced costs.

So, what is power factor correction?

Typically using capacitors to offset inductive loads, such as those produced by motors, power factor correction (PFC) tries to improve power factor and thus power quality. Ideally, a system should use all the power drawn from its source to perform useful work. This can happen if the current is in phase with the voltage. If a variation exists between the two, some of the energy from the AC mains is lost and does not perform work.

A measure of the effectiveness of using incoming power in electrical or electronic equipment is known as power factor. The technique of PFC attempts to achieve a power factor of 1 for any system, although most appliances will function effectively at a power factor of 0.95 also. Power factor is also known as the ratio of Real to Apparent power, terms which can be defined as follows:

The efficient functioning of the power supply is increased with the use of PFC systems, resulting in cost savings on electrical consumption and supporting green architecture.

There are a number of reasons why the process of PFC may be needed, such as:

Electrical equipment can become unstable and fail to work when the power factor is deemed poor. A system with a power factor of less than 90 percent will need power factor correction. Systems with poor power factors incur heavy energy costs, as an increased amount of current is needed to execute the same amount of work. Thus, improving power quality reduces power distribution system loads, reduces load on switching gear and cables, reduces costs.

To maintain systems that require power factor correction, the following levels should be regularly monitored, ideally every 6 months:

Now, traditionally, PFC equipment used a bank of capacitors to help reduce the total amount of electrical demand. The capacitors would offset an inductive load, or it would offset reactors in case of capacitive loads.

Enter the harmonic filter. A harmonic filter eliminates unwanted harmonics in electrical systems produced by non-linear loads, thus improving the performance of the equipment and reducing energy costs. Harmonic filtering is useful when the following situations occur:

Non-linear loads, such as uninterrupted power supplies (UPS), low-energy lighting and switched mode power supplies in personal computers, cause unwanted harmonic voltages and currents. By drawing current in short pulses, rather than a smooth wave-like manner, non-linear loads generate electrical harmonics, which create currents of varying frequencies that are reflected into the system, thus twisting the AC waveform.

It is in this way, by reducing the system’s efficiency, that harmonics reduce the power quality, leading to a lower power factor and ultimately higher energy costs. Harmonic filters sieve out a system’s electrical harmonics, reducing equipment overheating, tripping of fuses and breakers, improving power quality and thus reducing energy costs. By installing resonant circuits in series or in parallel, the harmonic currents are blocked or minimised, reducing harmonic voltage distortion.

The three main types of harmonic filters are:

Passive

Active

Hybrid