AC Input Current And Harmonics

Online Business

Harmonic currents are often generated in AC power supplies. A limiting of these harmonic currents requires legislation and the relevant standard for this legislation is EN61000-3-2 monitoring. There are four classes of equipment that are each shown for their own emissions standards on harmonic currents.

Class D: These are devices that are consuming less than 600 W of power such as monitors, televisions, and personal computers.

Class C: Lighting equipment and other devices commonly fall within this rating.

Class B: Portable tools and devices with larger power draw fall within this rating.

Class A: Is reserved for everything else that draws a large power limit.

When using equipment that falls under class A and B specification the limits for harmonics are set within absolutes. Class C equipment has a limit that is processed as a percentage whereas class D equipment has limits which are proportional to the power consumed by a device. C and D classifications require power supplies with a power factor correction. Further correction may be required for other categories of equipment.

Harmonic distortion can be a problem because it changes the efficiency of devices and it can often oversee devices if the extra current from a low power factor is not managed in some way. Neutral conductors within the device can quickly overheat if they are not sized to carry the extra harmonic currents that are available when devices are at high power load.

Connecting resistors and working on some type of power factor correction can help to prevent devices from overheating and make sure that a device can fall under required standards. If you would like to learn more about this technology, contact us today.

This post was written by Justin Tidd, Director at For nearly a half a century, Swartz Engineering has been at the forefront of industry safety. They are a family-owned company specializing in power distribution for the electrical industry. Our design ensures maximum flexibility for excellent reliability and a high return on investment.