Interference and overloading problems caused by harmonic frequencies can be eliminated by using ABB Control's harmonic filters. Harmonics cause overheating, damage and power losses in apparatus; generate electromagnetic fields; and decrease the quality of current, causing malfunctions. The solution is the ABB THF (Third Harmonic Filter), which removes third harmonics from the network.

Third Harmonic Frequencies are generated by equipment such as computers, discharge lamps, welding equipment, rectifiers, Uninterruptible Power Supplies (UPSs) and many types of home electronics.
Third harmonics are particularly problematic because they accumulate in neutral conductors. The 150 Hz alternating current which is generated in the neutral conductor can be stronger than the current in the phase
conductors.
A strong current in the neutral conductor can cause large power losses in the network, generate strong electromagnetic fields and cause overheating of cables leading to the risk of fire. Equipment is also affected by strong neutral currents, with power losses, strong magnetic fields, overheating, malfunctions of earth fault alarms and other kinds of interference and faults.
THF-filters remove about 95% of the third harmonic in the neutral conductor, greatly reducing harmonics problems. It has no effect on other frequencies but it also removes the 150 Hz current in the phase conductors and increase the life-time of capacitors, for example.
Harmonic filters also considerably decrease electromagnetic fields and power consumption.
ABB harmonic filters were installed and tested in a Scania factory in Sweden. The results exceeded all expectations. The neutral current decreased by 95% and the power consumption by 6%. The transformer load
went down considerably and the magnetic field measured in the premises was greatly reduced.
For installations currently in use, it has been shown that ABB's THF-filters reduce the energy consumption by up to 10% and may increase the lighting effect by up to 15% depending on the type of light source and compensation.
There are currently three different THF-filters available, rated at 63, 125 and 160 A. By connecting filters in parallel, a suitable filter for higher currents can be obtained.
The filter is sized according to the fuse of the power supply conductor and will be installed in a five-conductor system in the neutral conductor and in a four-conductor system at the star-point of the transformer.

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For further information contact:
ABB Control Oy, P.O. Box 622, 65101 VAASA
Tel.: +358 (0)10 22 4000
Fax: +358 (0)10 22 45708

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