Harmonics in Electrical Systems
Harmonics in electrical systems has become a significant challenge to electrical equipment manufacturers and engineers who are looking to keep up with rapidly advancing trends in power utilization. Harmonics is the term used to describe an irregular waveform, commonly referred to as a non-sinusoidal waveform, that is seen on the output of some electronic loads such as variable frequency drives (VFDs) and switched-mode power supplies (SMPS). Harmonics are a growing concern because they can lead to power and voltage issues, interfere with sensitive equipment, and cause excessive heating of components. Manufacturers and engineers need to be very aware of the potential risks when designing and installing harmonic generating devices. In this article, we will discuss the causes and effects of harmonics and how to reduce the impact of harmonics on electrical systems and equipment.
Harmonics can be described as a frequency component in an AC power system that is not a multiple of the fundamental frequency. This non-sinusoidal distortion can be caused by the presence of harmonic generating devices, such as VFDs, SMPS and certain types of electrical motors. These devices produce harmonics due to the non-linearity of the switching or conversion process that occurs within the device. These harmonics will then propagate through the wiring systems, often with higher voltage and current ratings than the fundamental frequency causing multiple harmonic orders to be present in the system.
When these harmonic frequencies are present, it can lead to several problems such as increased heating of components, power supply failure, equipment malfunction, potential power factor penalties and reduced system efficiency. Higher harmonic components can also cause resonance with system components, amplifying current and voltage levels and leading to overcurrent and overvoltage conditions. The heating of components can be caused by the additional current flow due to the harmonic frequencies, but this can be especially present in motors due to the increased nervousness, or increased losses that occur when the stator is supplied with the irregular waveform.
There are several measures that can help to reduce harmonics and its negative effects in an electrical system. Active power factor correction (PFC) is one way to help reduce harmonics by using an active power converter to reduce the level of harmonics by creating a more sinusoidal current waveform. This is especially beneficial when high levels of harmonic distortion is present in the system or where the prevailing power factor is below its ideal value.
Additional measures can be taken to reduce the levels of harmonic distortion by minimizing the amount of harmonic generating devices in the system, or by equipping existing devices with harmonic-filtering capacitors. Filtering capacitors should be chosen carefully as they are sensitive to certain harmonic frequencies, so they should be selected based on the level of harmonic distortion in the system.
Finally, harmonic mitigation can also be achieved by increasing the system’s wiring size and capacity, as this can reduce the impacts of harmonic frequencies in the system. Increasing the wiring size of the system is not always feasible, and other options might be the installation of an isolation transformer, the addition of an AC line-reactor to absorb some of the harmonics, or the addition of an external filter to contain harmonic distortion.
Harmonics in electrical systems is becoming an increasingly important topic, as the utilization of power becomes more efficient and devices become smarter. By recognizing the potential risks of harmonics, designers and manufacturers can better ensure that the electrical devices they create and install are safe and reliable. By following the proper harmonic mitigation strategies, the costs of harmonic damage can be minimized and the life span of equipment and systems can be increased.
