Avoid unnecessary energy costs and increase the efficiency of your systems – A comprehensive guide for engineers and plant operators.
What is the difference between the general power factor (λ) and the displacement factor (cos φ1)?
Der Displacement factor (cos φ1) describes only the phase shift between the fundamental wave of current and voltage. The general power factor (λ) on the other hand, additionally takes into account the harmonics caused by nonlinear loads such as frequency converters, and is therefore more meaningful for actual energy efficiency of modern industrial plants.
Why is a high power factor important for my manufacturing business?
A high power factor (ideally >0.95) means that you are using the electrical energy consumed efficiently. This results in lower electricity costs due to avoided reactive power charges, reducing the strain on your electrical equipment (cables, transformers) and minimizing energy losses in the grid.
What role do frequency converters and servo motors play in the power factor?
Frequency converters and servo motors are nonlinear loads that can generate harmonics. These harmonics lead to what is called distorted reactive power, which deteriorates the total power factor (λ), even when the displacement factor (cos φ1) is good. A correct design and possibly filtering is crucial here.
How can I concretely improve the power factor in my facility?
The most common methods are the installation of capacitor banks to compensate for inductive reactive power, the use of active reactive power compensators (SVG) for dynamic loads or high harmonic content, as well as the use of harmonic filters. The selection of energy-efficient drives and their correct sizing also contribute.
What costs can arise from a poor power factor?
A low power factor (e.g., below 0.9) can lead to significant additional costs . These include penalties from the energy supplier for consumed reactive power, higher energy costs due to increased transmission losses and potentially higher maintenance or replacement costs due to overloading of equipment.
What value should the power factor ideally be at?
Energy suppliers often require a power factor of at least 0.9 inductively. Technically and economically desirable, however, is a value of 0.95 or higher, to optimally minimize grid losses and costs. A value of 1 would be ideal, but is hardly achievable in practice.
How do I correctly measure the power factor, especially with drives using frequency converters?
With non-sinusoidal currents, as seen with frequency converters, a simple measurement of cos φ1 is not sufficient. The total power factor Lambda (λ) must be captured. Modern network analyzers integrate the power over at least half a grid period (10ms at 50Hz) to obtain accurate values despite harmonics .
What are the advantages of active reactive power compensators (SVG) over capacitor banks?
SVGs provide a more dynamic and precise compensation than capacitor banks. They can compensate both inductive and capacitive reactive power seamlessly and very quickly (within milliseconds) and often additionally filter harmonics. This is particularly beneficial in rapidly changing load profiles and a high share of nonlinear consumers.
The distinction is crucial: The general power factor Lambda (λ) takes into account harmonics from modern drives, while cos φ1 captures only the fundamental wave – essential for a correct assessment of energy efficiency.
A low power factor leads to higher energy costs, possible penalties and up to 46% greater line losses; an optimization increases the efficiency of the system and reduces the strain on the equipment.
Through targeted measures such as reactive power compensation (e.g., capacitors, SVG), harmonic filters, and optimized system design, the power factor can be improved to target values of over 0.95, which directly lowers costs and increases supply reliability.Learn all about the power factor cos φ, its importance for industrial drive systems, and how to optimize it to reduce costs and increase efficiency.
The power factor cos φ is a critical parameter for the efficiency of your drive systems. Understand the basics and learn how targeted actions can help reduce your energy costs and extend the lifespan of your systems. Do you need assistance in optimizing your drive technology? Contact now Contact with our experts!
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Introduction to the power factor (cos φ)
Power factor (cos φ) understand and optimize drive systems
An optimized power factor lowers energy costs and increases system efficiency. This article explains methods for optimizing the power factor cos phi and avoiding pitfalls to highlight cost-cutting potentials.
The true meaning of the power factor
The term “cos φ” is often incomplete. The general power factor Lambda (λ) captures, unlike the displacement factor cos φ1, also distortions from non-sinusoidal currents from frequency converters. This distinction is important for precise analyses of the energy efficiency grade. Understanding the active power factor
Challenges from modern loads
Modern industrial plants increasingly use power electronics (e.g., servo motors, LEDs). These nonlinear consumers generate harmonics that cause distorted reactive power. EU Regulation 1194/2012 requires a power factor of >0.9 for LEDs >25W.
Overview of solutions
Power quality analysis is the first step in optimization. Identification of the types of reactive power (fundamental, harmonic, asymmetry) is crucial for compensation measures (capacitor banks, active filters) to approach an ideal power factor Lambda (λ) of 1.Basics of the power factor and cosine phi
What is the Power factor (cos φ)?
Der power factor (λ) is the ratio of active power (P, kW, used) to apparent power (S, kVA, supplied), comparable to the usable content to the total volume of a drink. λ=1 means optimal energy utilization; λ=0.8 indicates 20% unusable power, underscoring the importance of a high power factor.
- Der power factor (λ), also known as the total power factor, defines the ratio of utilized active power (P) to supplied apparent power (S).
- A value of λ=1 signals ideal energy utilization without losses, a goal for any good power factor cos phi.
- The displacement factor (cos φ1) measures the phase shift between the fundamental waves of current and voltage.
- Cos φ1 corresponds to the total power factor λ only for purely sinusoidal currents and voltages.
- With nonlinear loads, the distortion factor (g = I1/I) affects the total power factor λ.
- Reactive power (Q) is energy that oscillates in the grid without doing work but stresses components and thus affects the power factor .
- Inductive consumers like motors need reactive power to build magnetic fields.
The difference between power factor and displacement factor
The displacement factor (cos φ or more precisely cos φ1) describes the phase shift of the current and voltage fundamental waves. It is only identical to the total power factor λ in purely sinusoidal curves. For nonlinear, harmonic-generating loads, the total power factor is given by λ = (I1/I) * |cos φ1|, where I1/I is the distortion factor g. A drive with a good λ = (I1/I) * |cos φ1|, wobei I1/I der Verzerrungsfaktor g ist. Ein Antrieb mit einem guten cos φ1 of 0.95 may have a reduced total power factor λof 0.85 due to harmonics. von 0,85 aufweisen. Determine three-phase power
The significance of reactive power
Reactive power (Q, kVAr) oscillates unused between producer and consumer but stresses network components. Inductive loads (e.g., motors) require it for magnetic fields; capacitive loads compensate for it. Example: 100 kVAr uncompensated reactive power at 400V means an additional 144 amps in the grid, illustrating the need for power factor optimization.Effects of a low power factor
Increased electricity costs and penalties
A low power factor increases electricity costs. Energy suppliers often impose penalties on industrial customers for falling below a threshold for the cos phi (often 0.9). These costs arise because the supplier has to provide more apparent power to meet the required active power when the power factor is poor. A shortfall below the threshold by 0.1 can already cause monthly additional costs of several hundred euros.
overloading of equipment
A low power factor requires a higher total current for the same active power. This causes greater heating and potential overload of cables, switchgear, and transformers, shortening their lifespan. A transformer rated for 1000 kVA delivers only 700 kW of active power at a power factor of 0.7 instead of 900 kW with an improved cosine phi of 0.9.
Increased energy losses
Transmission losses in lines (P_loss = I²R) increase quadratically with the current. Improving the power factor from 0.7 to 0.95 can reduce these losses by over 40%. The saved energy from an optimized power factor cos phi lowers costs and relieves the environment. Energy savings potential in motorsCauses of a low power factor
Inductive loads as the main contributors
Inductive consumers such as electric motors, transformers, or welding machines require reactive power to build their magnetic fields. Especially motors in partial load operation often exhibit a low power factor, sometimes below 0.7, which negatively affects the overall cos phi of the system. A single, incorrectly sized 50 kW motor can already cause significant reactive power.
- Inductive consumers: Electric motors (especially in partial load operation), transformers, and welding machines require reactive power for their magnetic fields, which affects the displacement power factor .
- Incorrectly sized motors: An oversized motor that does not operate under full load has a poor power factor power factor.
- Non-linear loads: Devices such as frequency converters, UPS systems, and LED lighting systems generate harmonics that worsen the λ = (I1/I) * |cos φ1|, where I1/I is the distortion factor g. A drive with a good power factor.
- Harmonics: These lead to distortion reactive power, which reduces the overall power factor (λ), even if the displacement factor (cos φ1) is good.
- Overcompensation: Too large capacitor banks can lead to an undesirable capacitive power factor and voltage increases.
- Long cable runs: Especially unloaded or lightly loaded long cables can act capacitively and affect the power factor cos phi power factor.
Non-linear loads and harmonics
Frequency converters, UPS systems, or LED systems are non-linear loads that generate harmonics. These harmonics cause distortion reactive power, which also deteriorates the overall power factor (λ) even with a good displacement factor (cos φ1). A B6 bridge rectifier in frequency converters can have a resulting cos φ1 near 1 of 0.85 due to harmonics. of only about 0.85.
Capacitive loads and overcompensation
Rarely do capacitive loads or overcompensation from too large capacitor banks cause problems with the power factor. Overcompensation leads to an undesirable capacitive power factor and can cause voltage increases. Long, unloaded cable runs can for example act capacitively and adversely affect the cosine phi power factor.Methods to improve the power factor
Reactive power compensation with capacitors
For compensating inductive loads and improving the power factor cos phi power factor, consumer-close capacitor banks have proven effective. These provide capacitive reactive power that compensates for inductive reactive power on-site and relieves the grid. A facility with 500 kW active power and a cos φ of 0.75 requires about 220 kVAr of compensation power to achieve a cos φ of 0.95. IE5 motors for efficiency
- Use of capacitor banks for compensating inductive reactive power directly at the consumer to optimize the power factor power factor.
- Use of Static VAR Generators (SVG) for fast, dynamic reactive power compensation and harmonic filtering, which improves the total power factor Lambda (λ) power factor.
- Installation of passive or active harmonic filters to reduce grid distortions caused by non-linear consumers and to stabilize the power factor..
- Optimization of system design by selecting energy-efficient motors (e.g. IE4, IE5) that inherently have a better cosine phi power factor.
- Correct sizing of drives to avoid partial load operation with poor power factor power factor.
- Avoiding idle operation of motors and other inductive devices as this unnecessarily lowers the power factor power factor.
- Utilizing modular system designs for Gear Boxes and motors for efficient drive solutions with good power factor.
Use of active reactive power compensators (SVG)
In rapidly changing loads or with many harmonics, Static VAR Generators (SVG) offer an advanced solution to improve the power factor.. power factor. SVGs dynamically provide (within milliseconds) both inductive and capacitive reactive power and additionally filter harmonics. power factor A manufacturing company improved its
from an average of 0.82 to a constant 0.98 by using SVG.
Harmonic filters for clean grids power factor cos phi When non-linear loads like frequency converters dominate, harmonic filters are often necessary to ensure an acceptable power factor. Passive or active filters reduce harmonic distortions in the power grid and improve the overall power factor λ. Precisely calculating motor power.
Optimizing system design
Even during system planning, a good power factor power factor can be promoted by selecting energy-efficient motors, correct drive sizing, and avoiding idle operation. Modular system designs for Gear Boxes and motors enable tailored, efficient drive solutions that contribute to a better cos phi. The use of an IE4 motor instead of an IE2 motor can for example improve the nominal loadpower factor by up to 0.05.Measuring technology and monitoring of the power factor
Modern power analyzers for precise data
Modern power analyzers (PQ boxes) are essential for accurate knowledge of power grid quality and the power factor cos phi power factor. They capture the displacement factor cos φ1, the overall power factor λ, harmonics, and various types of reactive power (Q-fundamental, D-Distortion), all of which influence the resulting power factor. A power analyzer can for example show that 30% of the reactive power results from harmonics and thus reduces the λ = (I1/I) * |cos φ1|, where I1/I is the distortion factor g. A drive with a good power factor.
Integration of measurement values into energy management systems
The integration of measurement values of the power factor. power factor and other grid parameters into an energy management system (EnMS) according to ISO 50001 is standard. This enables continuous monitoring of cos phi, trend analyses, and early detection of deviations to avoid penalty payments. Many systems alert when a threshold is undershot, e.g., when the power factor power factor falls below 0.92.
Importance of correct measurement with non-sinusoidal currents
With drives using frequency converters, the correct measurement of the power factor. power factor is critical. The multiplication of effective values of voltage and current, divided by the active power, often yields incorrect results for the power factor in non-sinusoidal waveforms. For an accurate measurement of the overall power factor Lambda (λ) the power must be integrated over at least half a grid period (10ms at 50Hz).
An optimized power factor results from deliberate planning and continuous monitoring. The distinction between the general power factor Lambda (λ) and the displacement factor cos φ is particularly critical for efficiency in modern drives. Applying these principles to improve the power factor cos phi power factor can reduce energy costs and increase system efficiency.
