Power Factor Correction
In general, the term power factor, the ratio of power actually used by the power actually delivered, and varies with the losses encountered in a particular system.
What are the causes of a low power factor? All inductive components within a system of distribution is necessary for the excitation of magnetic fields power. This applies to:
Asynchronous Transformers Induction Welder Induction regulators Fluorescent High Bay Lights Exhaust Magnets ClocksAll require electrical excitation current to the magnetic field needed to determine the function of individual elements of the system. Magnetic fields are a fact of life and power must be lived with.
Disadvantages
Here are some of the disadvantages that arise because of the presence of inductive circuits. First, the calculation of energy to the load you must:
Watt (W) = Volts (V) x Amps (A) xPower Factor
Initially increases as a power factor less than unity, the current in the system and therefore the system
Voltage to decrease with the following effects:
Low voltage lighting would reduce the light output. Induction motors at low speed (increased slip), the increased flows will need to do to meet the required loads. Increases due to increased flows of I2R power losses in cables and coils, toOverheating and consequent reduction in the lifetime of the devices. Capacity of contacts, switches, circuit breakers and fuses can be overcome with a reduction in the life cycle. Efficiency suffers as a whole, because more input in the development of performance improvement factor is absorbed losses.Advantages
After looking at the disadvantages now consider the advantages of improved power factor.
Ensure that the rated voltage of motors, lights, etc. applied for optimal performance. Reduction of losses in the circuits and cables. Reduction of losses in distribution transformers. Put your return is used in transformers and are not used in the manufacture-up losses. Allows existing transformers or additional load without overloading the need to support the capital costs of new transformers. Financial benefits from reducing peak demand charges.Simplified graphical representation will result
Power factor defined as the cosine of the angle betweenW and VA above, ie Cos (W / VA) is displayed. So with trigonometry, for any two given numbers, the rest can be solved. So, if we use (kWh) and reactive power (kvarh) know, we can calculate the power factor.
How to improve the power factor
As we approach the problem of improving the power factor? The usual method of making a capacitive system is through the introduction of static capacitors, the dielectric of chlorinated diphenyl impregnated paper reached the elements consist of asealed envelope, both in the circles of the load-source (for example in a sub-station) or near the inductive system.
Due to the fact that one of these capacitors, electrostatic first of these, are used to offset the income reflux inductive circuits. When connected to the circuit, the capacitors act as a reservoir of energy that can be exchanged between the field dielectric of the capacitor and the magnetizing current requirements of the inductive system.
Other methodsPower factor correction capacitors and synchronous motors are synchronous. Synchronous motors are excited by DC and therefore does not require a power delay for the purposes of the magnetization on the system. These machines are primarily for situations in which the rate constants are needed, determined on a wide range of loads, but are also able to operate in power factor between 0.8 units and leaders. This feature allows the system to benefit, in general, and an improved power factorResults. But unless the speed control characteristics are essential, would be the high cost of these machines, for reactive power compensation are just very uneconomical. Synchronous condensers are purely for situations which require large amounts of corrective measures kVAr, and not have the mechanical stress. These are not usually considered normal for industrial purposes.
Example:
If consumption of 100,000 kWh and 65 000 reactive kVArh was, then, using the methodologysaid, the power factor is 0.838. If we go above 0.95 to avoid surcharges, the capacity should be installed. This can be calculated by the installer.
Control of capacitors
Static control of capacitor banks from equipment contractor who in turn is controlled by a relay sensor. Basically a single-phase voltage and current to the relay, so they will be removed at unity power factor of the vectors of current and voltage applied to90 degrees.
Changes in this angular displacement will be either inductive or capacitive connect through the relay which then passes the contractors that the reactive kVAr required to correct the power factor, specified in or out of the system. Control relay can be mono or multi-phase, depending on the size of the capacitor equipment in use.
In a smaller system, the capacitor bank is likely to be close to the feed. The installation is the largest everCapacitors at different load centers would be located on the next distribution. In practice, however, is cheaper, the capacitor banks, along with multiple levels of supervision, possibly in a sub-station (which is also the possibility of interference of the relay).
Individual adjustment should be, for example, engine 37 kW and its volume. In this case, control relays would not be necessary, because the capacitors would be connected with the operation of itsthe engine. Individual correction can also be an advantage with welding equipment.
Level correction
Having established that there is a need for correcting the power factor, to what extent the correction should be applied?
This depends largely on the geographical location of the plant in question. While improvements in efficiency, it is desirable, the savings from low price / contract fees, which will inevitably determine whether a plant can be grownperformed. The power factor, under which bonuses are applied depending on the congestion charge zone network and from 0.85 to 0.98.
In general, the optimum is a residue from 0.95 to 0.98. At this level, both factors of customs, and efficiency are covered.
Maintenance
As for maintenance, as there are no moving parts, which have a capacitor, very little to go wrong. Capacitors can be controlled at every stage by measuring the current, what should beabout the same as indicated on the label. The only other maintenance is to clean the condenser bushings and check that the connections are tight.
Observed and entrepreneurs are moving contacts will be given every three months to ensure that there is no pitting or burning. Switches, if any, should be used at least once a week to clean the contact surfaces as well.
Under normal circumstances, that all the reactive kVAr no control relayMaintenance, but if in doubt get the manufacturer to find out there.
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