THD IN TOLERANCE
The PHF series IREM passive filters are characterized by a high capacity to attenuate harmonic disturbances and are designed to be applied in systems where current harmonic distortion must be reduced within defined limits.
The use of passive filters contributes to reduce the thermal and electrical overload caused by harmonic currents in installations that include variable speed motor drives, UPS, power rectifiers and other non-linear three-phase loads.
Typical applications include loads present in air conditioning, water treatment, oil sector and industrial automation processes in general.
Passive Filters (PHF) are additional filters usually installed on the power supply line of the drive.
The filters consist of a combination of inductor (filter inductor) -capacitor inserted in derivation from an asymmetrical series inductor (main inductor). The performance of the passive harmonic filters IREM PHF series are very high: they reduce the harmonic distortion in current from 100% of THDi to typical values lower than 5%; the filters are made up of capacitors that form a resonant circuit with a reactor that has a high impedance path at the fundamental frequency and a low impedance path at higher specific frequencies.
Passive filters are more commonly connected to individual loads in the system rather than to the common coupling point since the application requires a consistent load for effective harmonic mitigation.
The passive harmonic filter is installed in series with the line and therefore must be chosen according to the current absorbed by the load or by the group of loads. IREM passive harmonic filters guarantee excellent attenuation and do not need to be tuned with reference to the impedance parameters of the installation site.
HARMONICS IN ELECTRIC POWER SUPPLY
It is essential that the user is aware of the expensive problems and dangers associated with high levels of harmonics, especially in consideration of the important increase in the use of non-linear devices.
Harmonic components can significantly affect the electrical distribution network by acting on all of the connected structures and equipment.
Harmonic distortions cause the following problems in an installation:
- Conductor overtemperatures, in particular the neutral one in presence of single-phase distorted loads;
- MV/LV Transformer overtemperatures;
- Harmonic distortion of the voltage caused by the saturation of the MV/LV transformers;
- Overheating of standard power supply transformers with consequent expensive downtime and repairs or replacement of the transformer;
- Resonance with other reactive components on the same power line (e.g. power factor correction banks);
- Poor power factor;
- Resonance producing overvoltages;
- Increase in electricity supply costs due to harmonic losses;
- Interferences in telecommunication systems and equipment;
- Irregular operation of the control and protection relays;
- Intervention of automatic circuit breakers and other protective devices;
- Failure or malfunction of computers, motor drives, lighting circuits and other sensitive loads;