VFDs are a major source of harmonics in modern industries. This results in various issues, from power quality to power factor to transformer failures & much more.
Let’s look at some striking points on effectively suppressing these harmonics. Check the simple point-wise explanation of available solutions.
Line reactors for Harmonics
Install inductive reactors between VFD and power supply—the cheapest way to filter out harmonic distortions.
Passive harmonic filters for Harmonics
Installed between VFD and power supply. Use inductance and capacitance to filter harmonic. Effective at low frequencies but less at high frequencies.
Active harmonic filters
Use active power electronics to filter harmonic. More expensive but has better performance at high frequencies. Can filter specific harmonic and adjust to changes.
Multi-pulse VFDs
Use multiple rectifier sets to reduce harmonic order.
12-pulse VFD uses two 6-pulse sets, canceling the 5th and 7th harmonic. Similarly, 18-pulse and 24-pulse solutions are available, but complexity & prices become an issue with these systems.
Manufacturers like ABB, Siemens, Danfoss Drives, etc., have these solutions with them.
Active front-end VFDs
Use active power electronics to only shape current and filter harmonic inside the VFD. Highest mitigation but is the most expensive.
Matrix VFDs
Innovative technology for AC to AC conversion in VFDs. Some OEMs like Yaskawa Electric Corporation have a propriety technology product on this.
Some extra points to suppress VFD Harmonics
Use a motor with lower susceptibility to harmonics and a high power factor.
Properly ground and shield VFD wiring for minimum interference. Keep wiring short.
Optimize motor & VFD load vs actual application requirement. Improper VFD selection is another major cause of harmonic in Industries as people select oversize VFDs.
Read More on the cause of harmonics by clicking here.
If you are struggling with harmonics & related issues in your facility. You should consider seeking professional support from experts