Released: 18/3/2009

The particular strength of Schaffner ECOSine active filters is their ability to react to large load and harmonic patterns. Furthermore there is the inherent ability to respond to inrush current and, importantly to correct power factor. Take the example of a large rock crusher driven by a 400 kW motor. After complaints by other consumers about the flicker caused, the supply company forced the disconnection of the plant. A 1000 kVA generator put in place, barely coped with the starting up of the motor when very high reactive loads were encountered. During startup, the fluorescent lights in the control cab switched off. An active filter was installed and in due course the plant was reconnected to the supply system.
 
Active filters are also very effective in commercial installations. Such installations characterized by large numbers of electronic ballasts and IT equipment, generate very large harmonic distortion (much more than encountered in many industrial plants). Segregation of these loads is impossible and the use of active filters per phase on sub-distribution boards off loads the premises’ mains supply.
 
The new ECOSine Active filters from Schaffner are ideally suited to harmonic distortion mitigation as well as power factor correction for three phase circuits (three and four wire). Utilising Fast Fourier Transform (FFT) analysis to the 50th order, and performing the operation and consequent corrective current injection within 300 microseconds, the Schaffner ECOSine active filters provide a tailored solution to harmonics compensation. The response time is extremely fast so that the ECOSine filters combine the advantages attaching to FFT methodology with the response speed associated with so-called broadband active filters. The disadvantage of the latter is that they are unable to provide harmonic detail, merely correcting as far as possible overall current distortion.
 
The Schaffner ECOSine Active filters because of their high response speed are suitable not only for power factor correction but also for inrush current compensation thus making them ideal for taxing applications involving stand-by generator systems supplying mission critical loads where UPS systems are also in use, or in MG set applications where the loads demand a very high inrush current. Power factor correction is performed on displacement as well as harmonic distortion components. Power factor correction using capacitors is of limited use. The use of an active harmonics filter, on the other hand may, given an appropriate piece of apparatus such as the Schaffner ECOSine, mitigate harmonics as well as correcting effective power factor (i.e.: including displacement power factor).
 

Current THD %	Effective Power Factor
0	1.00
20	0.98
40	0.92
60	0.86
80	0.78
100	0.71
120	0.63
140	0.57

The Schaffner ECOSine Active filters are available in various frame sizes with compensating current ratings varying from 30 to 300 Amps, and in line voltages to 480 Volts. Overload capacities are considerable in order to allow for high transients. As an example, the 300 Amp rated model has an overload capacity of 750 Amps for 10 milliseconds. ECOSine filters can be operated in parallel with up to 5 units in circuit.
 
The ECOSine Active filters calculate compensating current profiles in microseconds, and permit the programming of harmonics to be compensated for. This is an invaluable feature because it allows for example, the selective elimination of those harmonics likely to induce resonance conditions (circuits with fixed or variable capacitive loads as encountered in displacement power factor correction equipment). The Schaffner ECOSine Active filters are therefore well suited to smoothly install into existing electrical reticulation networks.
 
The Schaffner ECOSine Active filters are highly serviceable, incorporating a modular construction, permitting extraction of various modules from the front, and also for safe, convenient disconnection of liquid cooling lines (used in filters with ratings above 100 Amps). ECOSine Active filters are provided with Ethernet, RS485 and Modbus interfaces.
 

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