Search

Premium Membership

Save 15% on Pro Premium Plan with discount code: UX778 (expires on October 31st). Study specialized LV/MV/HV technical articles and papers.

Harmonic distortion of the AC power line in HVAC systems
Harmonic distortion of the AC power line in HVAC systems (photo credit: ke-next.de)

Causes of power line distortion

Most adjustable frequency drives operate by using a bridge rectifier to convert the incoming AC voltage to DC voltage (see figure 1). An inverter in the drive then converts the DC voltage into a precise output voltage and frequency to control the speed of the motor.

General block diagram of an adjustable frequency drive
Figure 1 – General block diagram of an adjustable frequency drive

Drives today use a diode bridge rectifier to convert the AC line power into a fixed‐voltage DC bus (see figure 2). A DC bus capacitor bank is then used to filter out the AC ripple.

Diode bridge rectifier on a PWM drive
Figure 2 – Diode bridge rectifier on a PWM drive

While this results in a very efficient drive, it can cause disturbances on the AC power line due to the way the drive draws AC current.

Current cannot flow from the rectifier into the DC bus until the input voltage is greater than the DC bus voltage. As shown in figure 3, this only happens for a very short period of time for each phase.

Input with high peak current
Figure 3 – Input with high peak current

This causes a non‐sinusoidal current flow created by the input stage of the drive. In order to transfer the energy required by the motor in such a short period of time, the peak current must be high.

Title:Harmonic Distortion of the AC Power Line – Danfoss
Format:PDF
Size:365 KB
Pages:7
Download:Right here | Video Courses | Membership | Download Updates
Harmonic Distortion of the AC Power Line
Harmonic Distortion of the AC Power Line – Danfoss

Premium Membership

Get access to premium HV/MV/LV technical articles, advanced electrical engineering guides, papers, and much more! It will help you to shape up your technical skills in your everyday life as an electrical engineer.
More Information

2 Comments


  1. Pavel Chernikov
    May 26, 2014

    Detail description see IEEE Std 519-1992 section 4


  2. mark lodovice
    May 25, 2014

    thanks for the news it is very useful to me

Leave a Comment

Tell us what you're thinking... we care about your opinion! Please keep in mind that comments are moderated and rel="nofollow" is in use. So, please do not use a spammy keyword or a domain as your name, or it will be deleted. Let's have a professional and meaningful conversation instead. Thanks for dropping by!

  ×  three  =  twenty four

Learn to Design Power Systems

Learn to design LV/MV/HV power systems through professional video courses. Lifetime access. Apply a 15% discount code EAB77 and enjoy learning!

Subscribe to Newsletter

Subscribe to our Weekly Digest newsletter and receive free updates on new technical articles, video courses and electrical guides.