Some AC power consumed by the inductive load is used to maintain the magnetic reversal due to the phase shift between current and voltage. This energy is not used to perform valuable work and is a waste. Power factor correction capacitors reduce reactive power and the efficiency with which inductive loads consume AC power. Capacitors are essential components in power factor correction circuits, and this article discusses design considerations when using these components for power factor correction.
Reactive power of the inductive load
Inductive loads such as chokes, motors, induction heaters, generators, transformers, and arc welding equipment create an electrical delay usually called induction. This induction makes a phase difference between current and voltage. The signal current and voltage may vary due to the phase shift due to inductance. Negative energy is generated and returned to the power grid during these periods. If the two regain the same sign, they would require the same energy to create the magnetic field. The energy lost due to the magnetic reversal of an inductive load is called reactive energy.
Inductive AC loads are broadly classified as linear and non-linear devices. The current and voltage waveforms have identical sinusoidal profiles for linear loads. On the other hand, a non-linear load draws current at different frequencies, so the waveform of current and voltage varies. The current waveform is usually non-sinusoidal for most of the non-linear electric load. Examples of linear electrical loads include heaters, motors, and incandescent lamps. Non-linear devices include variable frequency drives, DC motors, programmable controllers, arc lighting devices, induction furnaces, uninterruptible power supplies, and personal computers. Non-linear electrical loads cause significant harmonic distortion in power distribution systems.
Electrical appliances or installations consume alternating current power with varying efficiencies. Some loads use energy efficiently, while others waste the most energy. Power factor describes how efficiently a load consumes alternating current power. This dimensionless quantity ranges from 0 to 1.
The total AC power consumed by an electrical device or device, also called virtual power, depends on two components: available power (active power) and reactive power. Precious energy refers to a device’s ability to accomplish a task. On the other hand, reactive energy does not produce any valuable work. Active power is usually measured in kilowatts and reactive power in kilovolts-amperes.
An ideal electrical load has a power factor of 1.0. This means that all the power consumed by the load is used for actual work. However, this isn’t easy to achieve with an actual electrical load.
Why is it difficult for an electrical load to achieve a constant power factor? Most electrical loads have inherent reactive properties that make achieving the ideal power factor challenging. It added a power factor correction capacitors to the network to compensate for the reactive load characteristics and overcome this limitation.
Power Factor Correction (compensation)
An electrical load with a low power factor consumes more power than is necessary to perform its task. This can lead to significant losses of power in the network and its loss of transformers. Increased energy consumption increases operating costs for equipment and facilities. A weak power factor also leads to a significant voltage drop in the distribution network. Electric suppliers commonly penalize industries where the power factor is less than a specific value.
Power suppliers encourage industrial consumers to improve their power factor for various reasons:
- You can significantly reduce your electric bill by improving the power factor.
- The higher power factor helps reduce efficiency losses in consumer transformers.
- Adding a power factor correction system can increase the appropriate capacity of the consumer power grid.
- A high power factor helps extend the life of electrical equipment.
The power factor correction grid reduces the power required by the load and improves the overall power factor. The electric load compensation grid allows for a good power factor, usually between 0.95 and 0.98. A power factor of 0.85 or less is generally considered a poor power factor by utility companies.
Capacitor-Based Power Factor Correction Circuit
There are various ways to improve the power factor or load fitting. A commonly used process is the addition of power factor correction capacitors to the network. How do capacitors help improve the power factor? The phase difference between current and voltage in AC circuits causes the magnetic pole to flip 50 to 60 times per second. Capacitors help improve the power factor by relaxing the reactive power supply line. Capacitors do this by storing magnetic reversal energy.
In most industries, capacitor systems controlled by power factor correction capacitors are installed to compensate for reactive power. When designing a power factor correction system, it is necessary to avoid adding excessive capacity to the network. Adding additional capacitance to the circuit can increase compensation.
For power factor correction, Semiconductor devices are widely used. Active compensation connects the semiconductor to the circuit to improve the power factor. Synchronous over-excited machines are also commonly used to improve the power factor of networks.
Most electrical loads, such as transformers, welding sets, induction motors, and furnaces, are inductive. Operating an inductive load requires both working power, usually measured in kilowatts (kW), and reactive power, conventionally measured in kilovolts reactive amperes (kVAR). The workforce is used to perform actual work, and reactive energy is used to maintain the magnetic field required for inductive loads. When combined, the power and reactive power are measured from the apparent power, usually in kilovolt-amperes (kVA).
Power factor measures the efficiency of an electrical load converting electrical energy into valuable work. It is the ratio of beneficial (working force) to total energy supplied (apparent power). A high power factor indicates that the electrical load is using energy efficiently, and a low power factor indicates that the connected electrical load is not using energy efficiently. I mean common power factor wastes a lot of energy and reduces the electrical system’s capacity. This can be caused by current and voltage phase differences or distorted current waveforms at the ends of the electrical load.
Power Factor Correction Solution
Connecting a suitable capacitor can correct the power factor drop caused by induction motors, transformers, and other inductive loads. Power factor degradation due to current waveform distortion is updated by adding a harmonic filter. Generating the required magnetic field for an inductive load creates a phase difference between voltage and current. The capacitor corrects the power factor by providing a maximum current that compensates for the lagging current. Power factor correction capacitors are designed so that the power factor is as close to unity as possible.
Power factor correction capacitors can significantly reduce the burden caused by the inductive load of the power supply, but it does not affect the operation of the load. By neutralizing magnetic currents, capacitors reduce losses in power distribution systems and help reduce electricity bills.
To prevent energy wastage, some distribution companies penalize consumers if their power factor falls below a specified value and offer incentives to consumers with a good power factor (usually 0.95 or higher). This prompts consumers to install power factor correction capacitors in their electrical systems. Adding power factor correction capacitors to your power grid includes reducing waste, optimizing voltage, increasing system capacity, and lowering your electric bill. The main variables to consider when selecting capacitors for power factor correction are load type, load constant, load size, load capacity, utility billing method, and load start method.
Different Types Of Installation For Power Factor Correction Capacitors
Power factor correction capacitors are usually installed as capacitor banks when substations and large installations exist. For sinusoidal or linear loads, they are easy to install and replace and can be established as individual capacitors that do not require separate switching. On the other hand, capacitor bank installations have a lower cost per kVA and provide precise capacitors for power factor correction when using automatic switching systems.
Fixed or automatic switching capacitor banks can be installed depending on the needs of a specific substation or facility. The constant power factor capacitor bank turns on when the inductive load is on and off when a single load is off. These capacitors are energized only when power factor correction is required. Facilities with multiple loads require frequent load conditions and power factor correction changes. Automatic condenser systems are suitable for such facilities. They prevent over-correction and under-correction.
Large inductive loads such as oil drilling rigs, wind turbines, large engines, arc furnaces, and automatic crushers have dynamic load characteristics. Such large dynamic loads require advanced automated capacitor systems with rapid response capabilities. A transient-free automatic capacitor bank is used for power factor correction applications with large inductive loads. Harmonics can significantly shorten the life of a capacitor bank. For loads that generate harmonics, you must add a harmonic filter. The harmonic filter then removes unwanted harmonic frequencies.
Types of Power Factor Correction Capacitors
Power factor correction capacitors are manufactured in many different types, sizes, and designs. The most commonly used types are made using metalized polypropylene film, but very few use polyester or metalized paper.
Bimetallic sheet capacitors are commonly used in applications that require a robust power factor correction solution. The technical papers that build these capacitors contain thin layers of metallic alloys. Polypropylene film separates form. These capacitors are made to withstand high temperatures and harmonic content. Bimetallic paper capacitors have many applications in power electronics. Metalized polyester film capacitors are small, lightweight, and have excellent capacitance stability. These capacitors are mainly used in DC applications but are also suitable for AC line filtering and power factor correction.
Inductive loads such as transformers, generators, motors, chokes, and arc welding equipment cause electrical delays, giving different current and voltage signals. Reaction energy is required to maintain magnetic reversal in an inductive load. Optimizing the power factor of AC loads to reduce reactive power can reduce the overall cost of operating inductive loads. The industry commonly uses capacitors to improve power factors and minimize energy waste.