Power quality filters boost density

Edited by the Engineeringtalk editorial team Jun 24, 2008

Active filters monitor power system currents in real time and then inject harmonic currents with exactly the opposite phase to the components that are to be filtered.

ABB has further extended its PQF series of microprocessor controlled active power quality filters for active harmonic filtering, load balancing and reactive power compensation to provide more power in fewer cubicles/enclosures.

The extensions to the PQF series cover both the PQFS range, designed to solve harmonic and neutral current related problems in commercial buildings and small industrial applications and the PQFM range for active filtering of lower capacity three-phase industrial loads.

The PQFS is a compact wall-mounting unit that has the versatility to work equally well with three-phase, three-wire or three-phase, four-wire systems.

It is ideally suited for smaller and medium loads where the equipment is connected between line and neutral or line and line or a mix of all these types.

The unique feature of load balancing between line and neutral enables the PQFS to reduce even the fundamental frequency current in the neutral, normally present due to unbalanced loading between phases, as well as filtering the harmonic currents from the line and neutral conductors.

Previously, the PQFS was available in three power ranges of 30, 40 and 60A RMS.

This has been extended with four further power ranges of 70, 80, 90 and 100A for both 240 and 415V applications.

This provides additional flexibility for an installer to meet their power quality needs with an extremely cost-effective solution based on a minimum of hardware units.

For example, a 240A PQFS solution can now be constructed from three 80A units, where four 60A units would be needed.

The PQFM is ideal for lower capacity three-phase industrial loads and can comprise of one master and up to seven slave units.

It is suitable for direct connection up to 600V and is offered in two voltage groups: 208 to 480V (V1) and 480 to 600V (V2).

The new models extend the V1 range to cover the power ranges of 70, 100, 130 and 150A.

As well as introducing new models in the PQFS and PQFM ranges, ABB has also optimised the hardware in its PQFK range, for active filtering of harmonics for commercial loads.

The PQF series also includes the PQFI range for heavy industrial loads.

The PQF series incorporates a number of standard features; including individual targeting of harmonics combined with curve setting functionality and closed loop control.

This allows achievement of standards such as G5/4, IEEE519 etc with optimal filter rating.

Reactive power compensation enables the load power factor to be increased to the desired level, while balancing loads between phases helps in reducing the negative sequence current.

Other features include a dynamic low loss control system, the highly advanced PQF-Manager user interface with network analysis capability, Modbus communication capability, real time stamp of events, parallel operation of units without derating, easy commissioning and so on.

The increasing use of nonlinear loads in all types of industrial and commercial applications has resulted in the introduction of potentially harmful harmonics into the power network that can lead to overheating of cables, motors and transformers, damage to sensitive equipment, tripping of circuit breakers and blowing of fuses as well as premature ageing of the installation.

ABB PQF active filters provide a reliable and cost-effective solution to this problem by continuously monitoring the current in real time to determine what harmonics are present and then injecting harmonic currents in the network with exactly the opposite phase to the components that are to be filtered.

The two harmonics effectively cancel each other out so that the feeding transformer sees a clean sine wave.

ABB PQF active filters are factory assembled and tested, ready to install and use at site.

They have a modular construction, which allows easy extension to cater for future load growth.

There is also no need to apply a de-rating factor when PQF units are coupled in parallel, which makes it feasible to achieve a high rating within a small footprint.

Since the PQF does not operate according to the conventional low harmonic impedance principle employed by passive filters it remains unaffected by changes in network parameters and cannot be overloaded.