SAF - active filter
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ACTIVE FILTER

Shunt active filters for harmonic currents The COMAR factory, established in 1968, was built with the future in mind. By installing superior equipment the factory has remained technologically advanced even by to-day's standards. Originally, the production was based on a wide range of "oil-paper" capacitors. The quality of the product was such that the COMAR brand was soon acknowledged both in Italy and world wide. A large investment in research and development during this early period made it possible to commence production of the innovative metallized polypropylene film capacitors. The...

In the last twenty years the fast introduction on the market of electronic equipment has brought along with their advantages many problems due to the noise on the electrical distribution network. In particular the most dangerous phenomena that degrades the power quality is the presence of harmonic currents generated by these non linear loads that are continuously changing their impedance during their working cycle, the absorption of current from the mains is not perfectly sinusoidal at the fundamental frequency, but is a sum of current with a different frequency multiple of the fundamental....

The presence of harmonic current in the installation can be a large problem because while the equipment works coupled with the impedance network, it creates also voltage distortion: this distortion can have a so high level to introduce problems with the other connected equipments in the installation as > vibration and overheating on the electric motors > noise and loss in the transformers > shortened life of components and conductors in the installation > erratic working of the control circuits that synchronize to the zero-crossing point of the sine wave. In fact there could be errors in...

SAF is designed to correct latest generation electronic load harmonic problems so: > it recognizes and compensates all the current up to the 50th harmonic order > it has excellent dynamic response to fast load variation > it compensates if network features change due to new machinery or equipment in the installation > every module is easily connected > it fits every kind of load so it will not be obsolete These good performance of SAF, with the possibility to connect it to existing an installation and its modular design allows the filter to give the right solution for every problem with...

In order to understand how SAF operates, look at the picture below there are three different blocks, each one showing different operating stages of the Active Filter: linverter block Regulation block Active Filter block schematic Main break switch; fuses; pre-charge circuit for electrolytic capacitors ; line filter; The main break switch with automatic turn-off and the pre-charge relay, allows the filter to turn-off and completely disconnect from the network when a internal fault occurs. So that an internal malfunction of the SAF (i.e. capacitor / microprocessor etc.) doesn't damage the...

solo armoniche Control filter chart The typical current emitted by Active Filter with a PWM modulation and hysteresis control is shown in the figure below where the current has a triangular shape with a carrier frequency of 10 kHz: This current is then modulated with the next rule: it changes continuously between the upper band and the bottom band, where it is forced to change. These two bands are shaped from the regulation block based on the load harmonic current and the internal regulation PWM control rules. Then a DC internal bus composed by two electrolytic capacitor banks, one with a...

flows to the load from the negative potential, reaching the lower side of the band control shaped (t2 time in figure) With this operations a current wave shape as the calculated one is flowing to the network, after that the waveform is filtering by the induction coil working in high frequency. In the same way (with the same method of control) the filter can generate current to correct the reactive power of the load, giving at the same time correcting the harmonics. In order to give a full power factor correction of the load, where it is necessary a reactive power greater than the one...

Active Filter Regulator The easy basic interface allows with leds to understand the system operation and the changing internal In particular the green led monitors the right function of the system during the compensation, and the start- up procedure, lighting in two different way to show the "pre-charge" operation and the "contactor on" The four red leds are monitoring the fault that occurs in the filter: > Power supply out of the rated range ("Supply voltage") > Fault of the contactor or of the inverter section start-up ("Contactor") > Fault of the internal temperature ("Temperature") >...

Power factor correction: It is possible to select on the regulator board the possibility of a partial power factor correction while filtering with a good final result. Voltage and current before the filtering (left waveforms) and with the filter with both the operation of harmonic pollution and power factor correction (right waveforms) In the two pictures it is possible to see the initial displacement between the voltage and the current of a non linear load before filtering that is with the current affected by harmonics. In the right figure it is possible to see that after the filtering the...

If SAF is working also as a power factor correction equipment, it is necessary to measure the parameter cosqpi for the fundamental components, remembering the relation Qi=V-li-sincp1. Now it's easy to find the right current for the filter for the reactive power compensation that is: When used only for harmonic mitigation it's possible easily find out the formula giving a zero value to the sinO term in the expression. Connection of SAF: shunt active filter for 3 phase - 3 wire system The C.T.'s transformer are one of the most important part of the filtering system, because is from them that...