Power Factor Correction

What is "Power Factor?" Power factor is a measure of how efficiently, or inefficiently, that electrical power is used by a customer. For industrial customers, a low power factor is generally caused by inductive loads such as transformers, electric motors and high-intensity discharge lighting. Customers that do not use electrical power efficiently are being charged additional fees for the inefficient use of power by their electric utility company.

What is "Power Factor Correction What is "Power Factor Correction?" An electric utility's power load on an electrical distribution system fall into one of three categories; resistive, inductive or capacitive. In most industrial facilities, the most common power usages are "inductive." Examples of inductive loads include transformers, fluorescent lighting and AC induction motors. Most inductive loads use a conductive coil winding to produce an electromagnetic field which permits the motor to function. All inductive loads require two different types of power for the motor to operate: Active power (measured in kW or kilowatts) - this power produces the motive force Reactive power (kvar) - this energizes the magnetic field of the motor. The operating power from the distribution system is composed of both active (working) and reactive (non-working) elements. The active power does useful work in driving the motor whereas the reactive power only provides the magnetic field. Unfortunately, electric utility's customers are charged for both active and reactive power.

Example: A customer's power factor drops, the system becomes less efficient. A drop from 1.0 to 0.9 results in 15% more current being required for the same load. A power factor of 0.7 requires approximately 40% more current; and a power factor of 0.5 requires approximately 100% (twice as much) to handle the same load. The answer to these problems is to reduce the reactive power drawn from the supply by improving the power factor. If an AC motor were 100% efficient it would consume only active power. However, since most AC motors are only 75% to 80% efficient, they operate at a lower power factor. This means inefficient and even "wasteful" energy usage and cost efficiency because most electric utilities charge penalties for poor, inefficient power factor. Simply installing capacitors will improve a commercial or industrial company's power factor and will result in savings on their electricity bill every month! Additional potential benefits for correcting poor power factor include: Reduction of heating losses in transformers and distribution equipment Longer equipment life Stabilized voltage levels Increased capacity of your existing system and equipment Improved profitability Lowered expenses

Understanding Power Factor    Consider a canal boat being pulled by a horse. If the horse could walk on water then the angle (Phi) Ø would be zero and COSINE Ø=1. Meaning all the horse power is being used to pull the load.  However the relative position of the horse influences the power. As the horse gets closer to the barge, angle Ø1 increases and power is wasted, but, as the horse is positioned further away, then angle Ø2 gets closer to zero and less power is wasted

Why do I need Power factor correction? Capacitive Power Factor correction (PFC) is applied to electric circuits as a means of minimising the inductive component of the current and thereby reducing the losses in the supply.  The introduction of Power Factor Correction capacitors is a widely recognised method of reducing an electrical load, thus minimising wasted energy and hence improving the efficiency of a plant and reducing the electricity bill. It is not usually necessary to reach unity, ie Power Factor 1, since most supply companies are happy with a PF of 0.95 to 0.98 How does it work? By installing suitably sized switched capacitors into the circuit, the Power Factor is improved and the value becomes nearer to 1 thus minimising wasted energy and improving the efficiency of a plant

ACTIVE & REACTIVE POWERS Power Factor Fundamentals ACTIVE & REACTIVE POWERS Most plant loads are Inductive and require a magnetic field to operate: Motors Transformers Florescent lighting The magnetic field is necessary, but produces no useful work The utility must supply the power to produce the magnetic field and the power to produce the useful work: You pay for all of it! These two types of current are the ACTIVE and REACTIVE components

Power Factor Fundamental Definitions: Working /Active Power: Normally measured in kilowatts (kW). It does the "work" for the system--providing the motion, torque, heat, or whatever else is required. Reactive Power: Normally measured in kilovolt-amperes-reactive (kVAR), doesn't do useful "work." It simply sustains the electromagnetic field. Apparent Power: Normally measured in kilovolt-amperes (kVA). Working Power and Reactive Power together make up apparent power.

Power Factor:The Beer Analogy Mug Capacity = Apparent Power (KVA) Foam = Reactive Power (KVAR) Beer = Real Power (kW) kVAR Reactive Power kVA Apparent Power Beer (kW) Mug Capacity (KVA) Power Factor = kW Active Power Capacitors provide the Foam (KVAR), freeing up Mug Capacity so you don’t have to buy a bigger mug and/or so you can pay less for your beer !

Power Factor Fundamental Power Factor : A measure of efficiency. The ratio of Active Power (output) to Total Power (input) Power Factor = Active (Real) Power Total Power = kW kVA = Cosine (θ) = DISPLACEMENT POWER FACTOR Total Power (kVA)  Active Power (kW) Reactive Power (KVAR) A power factor reading close to 1.0 means that electrical power is being utilized effectively, while a low power factor indicates poor utilization of electrical power.

Examples of Electric Equipment and Their Power Factor Different types of electric equipment have different Power Factors and consequently different efficiencies and current requirements: Name of Equipment Power Factor Percent Lightly loaded induction motor .20 Loaded induction motor .80 Neon-lighting equipment .30 - .70 Incandescent lamps 1 All types of resistance heating devices (e.g. toaster, space heater) 1

Typical Uncorrected Power Factor (Use only as a Guide)

Why do we care about Power Factor? In Industrial Facilities, Mostly Induction Motor loads Energy Efficient Motors not optimized for PF Low power factor is caused by oversized or lightly loaded induction motors Low power factor results in: Poor electrical efficiency! Higher utility bills ** Lower system capacity On the Supply Side, Generation Capacity & Line Losses Power Factor Correction Capacitors (PFCC) provide an economical means for improving Energy utilization

CAUSES OF LOW POWER FACTOR A poor power factor can be the result of either a significant phase difference between the voltage and current at the load terminals or it can be due to a high harmonic content or distorted/discontinuous current waveform. Poor load current phase angle is generally the result of Poor load current phase angle is generally the result of an inductive load such as an induction motor power transformer, lighting ballasts, welder or induction furnace, Induction generators Wind mill generators and high intensity discharge lightings. A distorted current waveform can be the result of a rectifier variable speed drive, switched mode power supply, discharge lighting or other electronic load.

Linear vs Non-Linear Until recently, most electrical equipment drew current in a “linear” fashion: Today, many electrical loads draw current in a “non-linear” fashion: v i Current (i) & Voltage (v) are both “Sinusoidal” Current (i) is periodic, but not “sinusoidal” v i

What produces “Non-linear” Current? Computers Fax Machines Copiers M Variable Frequency Drives Electronic Ballasts Almost anything electronic

Time vs Frequency f1 + f3 + f5 + f7 = Time Domain Frequency Domain 60 Hz + f3 180 Hz + f5 300 Hz + f7 420 Hz =

POWER FACTOR CORRECTION Power factor decreases with the installation of non resistive loads such as induction motors, Transformers. Lighting ballasts and electronic equipments. Power factors can be corrected by using capacitors. These are rated in electrical units called VAR or KVAR.One VAR is equivalent to one volt of reactive power. VAR then are units of measurement for indicating just how much reactive power the capacitor will supply. As reactive power is usually measured in thousands the letter K is used for thousand. the capacitor KVAR rating then shows how much reactive power the capacitor will supply. Each unit of the capacitor's KVAR will decrease the inductive reactive power demand.

Total Harmonic Current Distortion Is Same As Total Demand Distortion (TDD) + = ´ å I TDD h 2 4 1 100 L % 3 ¥

Total or True Power Factor (TPF) (DPF) x (Harm Coefficient) KW DPF = = Cos f KVA 1 Harm Coefficient = Total or True Power Factor has two components – displacement power factor and harmonic power factor. However, harmonic PF is not a term used today. We call it the harmonic coefficient. The product of these two values equals the true PF. 1 + TDD2 TPF = Total or true power factor DPF = Displacement power factor Harm coefficient = Harmonic power factor = Cos d

How do utilities charge for Power Factor? Utilities recoup the cost of providing reactive power in different ways….. kVA billing: utility measures and bills every ampere of current including reactive current. kW demand billing with Power factor adjustment: utility charges according to kW demand and adds a surcharge for power factor, typically in the form of a multiplier applied to kW demand. kVAR Reactive Demand charge: A direct charge for use of magnetizing power. (example:$ 4.50/kVAR)

MOST COMMON POWER FACTOR RATE CLAUSE BILLING KW DEMAND = ACTUAL KW DEMAND X BASE PF/ ACTUAL PF

POWER FACTOR CORRECTION METHODS Static Var Compensator(SVC) Fixed Capcitors Switch Capacitors Synchronous Condensors Static Synchronous Compensator(STATCOM) Modulated power filter capacitor compensator

ADVANTAGES OF POWER FACTOR CORRECTION Eliminate Power Factor Penalties Increase System Capacity Reduce Line Losses in distribution systems Conserve Energy Improve voltage stability Less total plant KVA for the same KW working power Improved voltage regulation due to reduced line voltage drop Reduction in size of transformers, cables and switchgear in new installations Increase equipment life Save on utility cost Enhance equipment operation by improving voltage Improve energy efficiency

DISADVANTAGES OF LOW POWER FACTOR Increases heating losses in the transformers and distribution equipments. Reduce plant life. Unstabilise voltage levels. Increase power losses. Upgrade costly equipments. Decrease energy efficiency. Increase electricity costs by paying power factor surcharges.

Electronic Switch –Transient Free Fuses SCR-Diode De-tuned Inductor L1 L2 L3 Three phase capacitors connected with solid state switching elements which are controlled by a Transient Free Controller Solid State Capacitor Switching Modules provide reliable, high speed, transient free operation. Each Capacitor switching Module switches up to three capacitor groups (450kVAR) using double phase electronic switches for each three phase capacitor group. Fuses protect the electronic switching elements against short circuit currents. Custom designed Iron Core reactors in the AT6000 de-tune the network, prevent resonance and remove up to 50% of the 5th harmonic. AT6000 is recommended for power factor correction in networks with greater than 15% non-linear loads. For a non-linear load percentage of less than 15%, the standard AT5000 bank is suitable. AT6000 provide the following: Tunes the network below the first dominant harmonic, usually the 5th or 300 Hz May absorb up to 50% of the 5th harmonic current depending on network characteristics A heavy steel welded yoke to clamp the top and bottom laminations as opposed to traditional bolt through clamping AT5000 vs AT6000 example: suppose a transformer supplies 2000 kW. Of this, 400 kW is used by non-linear devices (AC or DC Drives, power converters etc.) The non-linear load percentage will be greater than 15% (400/2000) and, therefore, an anti-resonant TFRC (AT6000) system is recommended. Capacitors - Heavy Duty Dry Capacitors feature self healing metalized polypropylene film elements provide good heat dissipation resulting in longer life Elements for 480V networks are rated 590V +10% overvoltage; elements for 600V networks are rated 690V +10% overvoltage Unique open air-element design - modular design

CONCLUSION By observing all aspects of the power factor it is clear that power factor is the most significant part for the utility Company as well as for the consumer. Utility company rid of from the power losses while the consumer free from low power factor penalty charges. By installing suitably sized power capacitors into the circuit the Power Factor is improved and the value becomes nearer to 1 thus minimising line losses and improving the efficiency of a plant.

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