What is a capacitor bank and why is it used?
The Cost Implications of Low Power Factor Operation:
Apparent power (S) (often measured in kVA) is the product of RMS voltage and current values and is made up of two very different sorts of power components:
Actual or true power (P) is given to the load (often measured in kW), which over time reflects electrical energy converted or transformed into other forms such as heat, light, and mechanical work.
Reactive (or wattless) power (Q) (usually measured in kVAR) represents the power required to establish magnetic fields around inductive components (lagging reactive power) and electric fields in capacitive components (leading reactive power) and then supplied back into the supply system as these fields fall to zero.
Power factor is defined as the ratio of actual power (P) to apparent power (S) given to a load. It also denotes the cosine of the phase angle between voltage and current at every point in a power supply system, electrical infrastructure, or individual circuit.
As a result, because phase angles can range from 0 to 90 degrees, power factors can range from one to zero, depending on the nature of the load.
Power factor (pf) = P/S = cosΦ
Low power factor operation is undesirable for the following reasons:
(c) The installed plant of the supply company can only withstand a specific amount of kVA before becoming overloaded. As a result, a customer's kVA need for the energy (kWh) they really utilize is unreasonably high due to the low pf performance of their electrical infrastructure. In actuality, a low pf consumer consumes more generating, transmission, and distribution equipment and produces more losses than a comparable consumer running at a higher pf. This, in turn, limits the number of clients who may be served within the capacity of any particular system. As a result, supply firms charge a fee based on the maximum kVA given by the consumer as well as the cost per kWh consumed.
As a result, it makes financial sense for an energy user to run their loads at as high a pf as is financially feasible in order to avoid incurring an extremely high maximum demand cost.
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Sites with a considerable reactive power requirement for large inductive loads, such as a high proportion of electric motors, arc welding equipment, induction furnaces and induction heating equipment, overhead cranes, etc., tend to operate at low power factors.
A power factor less than 0.8, as a general rule, indicates that some type of pf correction is financially worthwhile.
In general, it is preferable to connect pf improvement equipment as close to inductive loads as feasible, because all conductors and control equipment benefits from a lower current from their point of connection on the supply side.
NB - The real LOAD current remains constant; only the supply current changes up to the point where the pf enhancement equipment is connected.
Most industrial and commercial consumers with a large number of inductive loads, on the other hand, do not fit each individual item with pf improvement equipment (capacitors), but rather install banks of capacitors at the supply intake position where capacitance is automatically switched in and out to maintain the overall installation's pf at the desired level (typically 0.95 lagging) as the daily load changes.
Individual capacitors are used in some goods such as discharge lights, welding transformers, and induction heating equipment because they allow for the use of smaller cables and switchgear up to the point of connection.
Some facilities use synchronous motors to increase overall pf since these machines can operate at leading power factors. They have dc supplies to their rotors, and it is the tuning of these that allows the motor to run at a LEADING pf.
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