Please refer to following table for the power factor of the most common loads Device Load cos φ tg φ Ordinary asynchronous motor 0% 0.17 5.8 25% 0.55 1.52 50% 0.73 0.94 75% 0.8 0.75 100% 0.85 0.62 Incandescent lamps   1 0 Fluorescent lamps   0.5 1.73 Discharge lamps   0.4 to 0.6 2.29 to 1.33 Resistance furnaces   1 0 Induction furnaces   0.85 0.62 Dielectric heating furnaces   0.85 0.62 Resistance welding machine   0.8 to 0.9 0.75 to 0.48 Single-phase static arc-welding centres   0.5 1.73 Rotary arc-welding sets   0.7 to 0.9 1.02 Arc-welding transformers/rectifiers   0.7 to 0.9 1.02 to 0.75 Arc furnaces   0.8 0.75 Cos φ of the most commonly-used devices.

Active harmonic filters are parallel filters (which means the current doesn’t go through the filter) that are used to reduce, or mitigate, harmonics to tolerable levels as defined by IEEE-519.  Active filters use a set of transistors and capacitors to filter (or clean) the current wave by injecting inverse currents to cancel out the undesired harmonic components.  Active filters are significantly more expensive than passive filters and take up more space.  Size is an immense factor in system design today and should be accounted for when deciding on what type of harmonic filter is right for you. Active filters can work with multiple drives; when the active filter reaches its limit, it won’t overload. In addition, if an active filter breaks, it won’t stop the motor (since current isn’t going through the filter); it just won’t filter the current wave. AHFs can take care of several other power quality problems by combining different functions in a single device: ⦿ Elimination of harmonic currents and voltages. ⦿ Power factor correction (lagging or leading). ⦿ Voltage variations (sags & swells) reduction. ⦿ Voltage fluctuations (flicker) mitigation. ⦿ Load balancing in three-phase systems. ⦿ Controlled & selectable harmonic generation. How AHF Works? An Active Harmonic Filter is a power electronics-based device connected in parallel with the load that requires harmonics mitigation. AHF works as a controlled current source providing any kind of current waveform in real time. AHFs monitor the currents of the load and compensate any produced harmonic currents by generating a compensation current for each selected harmonic order in phase opposition to the harmonic current. Result is  reduction on the levels of harmonics of the installation to the limit requested by the customer ensuring compliance with power quality standards and recommendations.  ZDDQ--excellent manufature of active harmonic filter/static var generator.

ZDDQ’s STATCOM gives customers the ability to solve power quality issues, maximize productivity and increase profitability. A STATCOM is a voltage regulating device. It is based on a power electronics voltage source converter (VSC) and can act as either a source or sink of reactive AC power. It is a member of the flexible AC transmission systems (FACTS) family which detects and instantly compensates for voltage fluctuations or flicker, as well as controls power factor. As a fully controllable power electronic device, the STATCOM is capable of providing dynamically both capacitive and inductive VArs. Compared to a SVC (static VAr compensator), a STATCOM has faster response time and better reactive power capability. STATCOM delivers maximum output current even at low system voltages, reducing the need for harmonic filter. ZDDQ is an excellent power quality solution Supplier from China.

Reduce Overheating Active Harmonic Filter reduce overheating of transformers,switchboards, and cables due to increased current. Reduce Nuisance Tripping Active Harmonic Filter reduce Nuisance tripping of thermal protection devices such as overloads and circuit breakers. Reduce Overloading High Harmonic levels can overload neutral conductors. Active Harmonic Filter is the best solution for this. Reduce Equipment Failure Active Harmonic Filter reduce poor power factor and premature failure of Power Factor corretion capacitors. Improve Reliability Active Harmonic Fitler avoid overheating of internal components,PLCs,DCS, and other low voltage power supplies.

Active Harmonic filters are systems employing power electronics. They are installed either in series or in parallel with the nonlinear load to provide the harmonic currents required by nonlinear load and thereby avoid distortion on the power system. The active filters inject, in opposite direction, the harmonics drawn by the load, such that the line current Is remains sinusoidal. They are effective and recommended for the commercial installations comprising a set of devices generating harmonics with a total power rating less than 200 kVA (variable – speed drives, uninterruptible power supplies [UPSs], office equipment, etc.). Also, they are used for the situations where the current distortion must be reduced to avoid overloads. Where: Is = source current; Iact = current injected by active filter; Ihar = harmonic current generated by nonlinear load. In general, active harmonic filters(AHF) are special harmonic filters. Active filter is usually utilized in the form of a parallel filter. Note that this part does not analyse the differences between parallel filters and serial filters. Sometimes, for the term ‘active filter’, the term ‘active harmonic filter’ is more common. In contrast to the passive filter described above, this filter improves everything right down to the sinusoidal shape of currents or voltages at the connection point. Active filters supply harmonic currents used by the consumer so that, under ideal conditions, only the fundamental frequency current is still obtained from the distribution network of the local distribution system operator (power utility). Most active filters are digital (i.e. the harmonic spectrum is determined by amount and phase location from the current measurement and an appropriate counter-phase current spectrum is generated). Most of the ‘active harmonic filters’ on the market today are current controlled and can filter the harmonic current of a measured load. The harmonic level from the MV or the harmonic generators outside the measuring circuit are not affected by this. AHF can filter harmonic currents up to their nominal current, whereby an individual so-called derating factor (reduction factor) must be considered for every specific frequency. Examples of typical applications of the active filter are: 1.Distribution networks in office buildings with a lot of nonlinear loads which cause a total harmonic distortion of THD-I · S/Sr > 20%. 2.Distribution networks whose voltage distortion caused by harmonic currents must be reduced to avoid malfunctions of sensitive loads. 3.Distribution networks whose harmonic current must be reduced to avoid overloads; in particular, those of the neutral conductor. Some additional typical applications are as follows: 1.Power inverter load with high harmonic feedback and low reactive power requirements. 2.Networks with a high share of the third harmonic due to the use of single-phase consumers. Some important characteristics of active filters are as follows: 1.Most active fi...

Inside structure of Automatic Power Factor Correction Panel without reactors

Inside structure of Automatic Power Factor Correction Panel

To select a capacitor bank, there are two major compensation systems or types. 1.Fixed type capacitor banks: The reactive power supplied by the bank is constant irrespective of the variations of the power factor and load of the receivers and, therefore, of the reactive energy Consumption of the installation. These banks are switched on: ◆either manually by a circuit breaker or switch, ◆or semi‐automatically by a remote‐controlled contactor This type of bank is generally used in the following cases: ◆Constant load electrical installations operating 24 hours a day, ◆Internal reactive compensation of transformer, ◆Individual compensation of motor. 2. Automatic type capacitor banks: ◆The reactive power supplied by the bank can be modulated according to the variations of the power factor and the load of the receptors and, therefore, of the reactive energy consumption of the installation. ◆This type of bank is composed of a parallel combination of capacitor steps (step= capacitor +contactor). Switching all or part of the bank on and off is controlled by a incorporated VAR meter regulator. ◆h a banks are generally used in The following cases: (1).variable load electrical installations, (2).compensation of main switchboards (MDB) or major outlets, (3).Installation of a bank with a power greater Than 15% of the Transformer power S(kVA). Fixed capacitor banks Automatic capacitor banks

One contributing element to power quality is power factor. Power Factor Correction (PFC) aims to improve power factor, utilising capacitors to offset usually inductive loads, for example motors. PFC systems increase the efficiency of power supply, delivering immediate cost savings on electricity. Power Factor is a measure of how effectively incoming power is used in your electrical system and is defined as the ratio of Real to Apparent (total) power where: • Real Power is the power that actually powers the equipment and performs useful, productive work. • Reactive Power is required by some equipment (e.g. transformers, motors and relays) to produce a magnetic field for operation; however it does not perform any real work. • Apparent Power is the vector sum of Real and Reactive Power and corresponds to the total power required to produce the equivalent amount of real power for the load. Power Factor Correction may be required where a system has a power factor of less than 90% (or 0.9). A poor power factor can contribute to equipment instability and failure, as well as significantly higher than necessary energy costs since it means that more current is required to perform the same amount of work. By optimising and improving the power factor, the demand on the electricity distribution system is reduced. Power Factor Correction equipment achieves a decrease in the total amount of electrical demand by using a bank of capacitors to offset an inductive load (or reactors if the load is capacitive).