Active Power Filter – APF2000

APF2000 Delta’s Active Power Filter APF2000 is your key to a clean grid for more efficient production. Today’s automation equipment benefits us with a more convenient life style and cost savings from higher production efficiency, however it can also bring significant power distortion problems that can lead to energy loss, increasing costs and many other power quality issues.

Power quality is a major influence on power efficiency. A clean and efficient power system normally generates a sinusoidal current waveform, but the electric equipment used in today’s industrial automation industry generates non-sinusoidal currents that tend to cause power quality problems. Voltage or current distortion, reactive power impact, and unbalanced loads, are common problems that lower power reliability and power efficiency and also increase operation costs. Major concerns in the industrial automation industry are how to improve power quality and how to manage power grids.

Delta’s APF2000 adopts the industry’s highest standard 32-bit digital microprocessor to instantly compensate for all types of harmonics for ultimate power quality improvement. Perfect control of harmonic distortion reduces power loss and heat generation. The APF2000 is compact in design for all users to manage their space efficiently and is mounted with 65,536-color TFT HMI for more realistic images and a vivid display. The ultimate mission of Delta’s APF2000 is to provide you with improved power quality, lower energy loss and lower maintenance costs.

Energy Bill Consultation

Features & Benefits

Delta’s Active Power Filter – APF2000 is a power filter device that can monitor load current and filter harmonics in real-time to maintain a clean line current. It monitors the load current in real-time using a current transformer and injects the exact opposite phase to the network of components that are to be filtered. It can also provide leading and lagging reactive current in real-time to improve the power factor and compensate reactive power.

APF2000 Specs1


  • Excellent filtering result and provides harmonics compensation up to 90%

APF2000 Specs2

  • Compensation for harmonic current, reactive power, power factor and load balancing

APF2000 Specs3

  • Advanced Modular Design: Safe, Reliable, Labor-saving

APF2000 Specs4

  • Provides diversified communication network and optional fieldbus cards


  • Metallurgy and petrochemicals industries: rectifiers, converters, rolling mills, electric arc furnaces, medium frequency furnaces, inverters
  • Chemical and electrolysis industries: rectifiers, calcium carbide furnaces, electric soldering, inverters
  • Mechanical industries: rectifiers, rolling mills, inverters, electric arc equipment
  • Metal, paper, plastic processing and textile industries: rectifiers, rolling mills, inverters, electric arc furnaces, electric furnaces
  • Transportation industries: rectifiers and inverters for electric vehicles, electric motorcycles and metro systems
  • Automobile manufacturing industry: soldering equipment, car painting equipment, battery chargers and inverters
  • Telecommunication, medical and construction industries: Server stations, EPS, UPE, converters, chargers, inverters


Power Factor

What is power factor?

Power factor measures how effectively your equipment converts electric current (supplied by your power utility) into power output, such as light, heat or mechanical motion. Technically, it is the ratio of active or usable power, measured in kilowatts (KW) to the total power (active and reactive) measured in kilovolt amperes (KVA).

power factor

What is power factor correction?

Power factor correction is a method of improving a low power factor on a power system by traditionally installing power factor correction capacitors or harmonic filters that increases the ratio of active/usable power to total power. It reduces the amount of kVAR that is required from the utility, and therefore may reduce the customer’s energy bill.

Active Harmonic Filters (APF2000) and Static Var Generators (SVG2000) both provide reactive power to compensate for poor power factor which is caused by inductive loads. Energy Utilities are beginning to charge their customers on kVA rather than kW usage as this power is a measure of the true strain on the network’s infrastructure. Since kVA (Apparent Power) is a representation both kW (Real Power) + kVAR (reactive power), it would be in the customer’s best interest to reduce the wasted kVAR on site and therefore reduce the kVA demand, which would result in savings on their energy bill. Below is a visual representation of this where a common induction motor requires kVAR.


power factor diagram 2

This figure shows kVAR 2 inductive & non- linear loads which require kVAR. This entire portion of kVAR is supplied by the utility and the kVA demand tariff is at its maximum


APF design

This figure is a representation after a Delta Active Power Filter has been installed on site, which provides a portion of reactive power (kVAR) to the loads requiring it. This reduces the amount of kVAR required from the utility and therefore will reduce the kVA demand tariff.


 Why does power factor matter?

A poor power factor may cost your company money through inefficiency and increase the carbon footprint. If the site has a low power factor, it will demand more power than it is in fact using. This will create additional charges to the electricity bill.

What is the cost of low power factor to my business?

If your company is demanding more power than it is actually using, it can be paying avoidable charges on its monthly electricity bill. Some electrical utilities charge users a penalty when their power factor drops below a certain level and the power factor surcharge covers the electric utilities cost of supplying your power system with additional reactive power.

Below is an example of a bag of crisp that has a low power factor of 0.3. In this example you pay for the entire packet (kVA), yet you only use the chips content (kW).


Chips example

What causes low power factor?

Equipment that creates a magnetic field to function, such as electric motors, transformers, arc welders, are the main causes of a low power factor. The energy used to create the magnetic field that functions these pieces of equipment, add additional loads to your power system. If harmonics filters such as the Active Power Filter (APF2000) are not installed, your power system will draw this excess energy from the utilities and cause a low power factor, which results in excessive charges.

What are the benefits of power factor correction?

Saving money on electricity is the most beneficial part of installing power factor solutions. If you are taking measures to reduce your electricity demand, you will achieve lower monthly demand charges. There are also environmental benefits associated with power factor correction, as your company’s power system is putting less demand on the electricity grid and therefore reduces the carbon footprint.

Can you correct poor power factor?

Delta provides an Active Power Filter solution (APF 2000). The APF2000 mitigates harmonics and provided reactive power compensation to the electrical infrastructure. This solution will achieve a power factor >0.96 that improves the efficiency of the site. This solution will be professionally sized and recommended by qualified engineers at Delta Energy Systems.



What are harmonics?

Harmonic currents and voltages are integer multiples of a systems fundamental frequency (50Hz in Australia). The 5th harmonic will have a frequency of 250Hz (5 x 50Hz) and the 7th will be a 350Hz (7 x 50Hz) current carrying frequency. These are unwanted frequency components of currents running through the entire electrical network infrastructure on site.


How do harmonics affect the fundamental frequency waveform?

The fundamental frequency component which is always predominant becomes distorted by the addition of harmonic sinusoidal waveforms. The level of measured distortion is given as Percentage Total Harmonic Distortion (THDi%-Current or THDv%-Voltage).


Where do harmonic currents come from?

The equipment we use today (computers, automated process control equipment, variable speed drives and solid state power conversion equipment) are all examples of non-linear loads that contain circuits that convert alternating current (ac) to direct current (dc). When these are energised, the power conversion circuits (themselves very sensitive to power) create harmonics that can severely distort the power supply and cause problems for others connected to the same source. Harmonic currents can overload wiring and transformers, creating heat and, in extreme cases a fire.

What harmonic orders are affected by common non-linear loads?

Single-phase line-to-neutral rectifier loads, such as switch-mode power supplies in computer equipment, generate current harmonics 3rd, 5th, 7th, 9th and higher. The 3rd will be the most predominant and typically the most troublesome. 3rd, 9th and other odd multiples of the 3rd harmonic are often referred to as ‘triplen harmonics’; they add arithmetically to the neutral and are also considered zero sequence currents. Line-to- neutral non-linear loads can be found in computer data centres, telecom rooms, broadcasting studios, schools,

financial institutions, etc

However, the majority of Industrial Applications will have high harmonics in the 5th, 7th, 11th, 13th orders and the amount of harmonic current content in the neutral wire (3rd order harmonic frequency) will not be an issue unless there is a significant single phase-non-linear loads connected to the same supply. The 3 Phase/3 Wire Active Power Filters is the preferred solution if the harmonic current in the neutral wire is insignificant. Most variable frequency drives have a 6 pole IGBT internal architecture that produces harmonic currents at the output of the inverter which are seen by the motor. See the diagram below for a formula example of the primary harmonic orders which will be affected.

harmonic orders

Harmonic orders typically reduce in magnitude as they increase in frequency. In the variable speed drive example above, the 5th and 7th order will have a greater impact than the 11th and 13th orders. Below is the harmonic spectrum for a typical 6 pole IGBT variable speed drive.

harmonic magnitude

What problems do harmonics create?

Most power systems can accommodate a certain level of harmonic currents but will experience problems when they become a significant component of the overall load. As the higher frequency harmonic currents flow through the power system, they can create problems such as:

  • Overheating the electrical distribution equipment, such as cables and transformers.
  • High voltages and circulating currents caused by harmonic resonance
  • Equipment malfunctions due to excessive voltage distortion.
    Increased internal losses in connected equipment resulting in component failure and shortened lifespan. • Metering errors
  • Lower system power factor preventing effective utilization

What causes harmonic voltages?

The electrical distribution has harmonic impedances that cause the load-generated harmonic current to produce harmonic voltages (Hvoltage = Iharmonic x Zharmonic).

harmonic voltages

What is the solution to mitigate harmonic currents?

The original solution to correcting power factor was is to install power factor correction capacitors to provide the VAR’s and install LC trap tuned filters (e.g. tuned to 250Hz/5th order) that provide a low impedance path in order to mitigate harmonic currents. Active technology however is a more professional solution to mitigate a range of harmonic orders whilst simultaneously improving the power factor. The mitigation of these harmonics is done by injecting an opposite phase pulse for the specific frequencies to be moderated. The visual representation is shown below:

mitigate harmonic currents

Is there a solution to the problems caused by harmonics?

Mitigation of harmonic currents will solve all harmonic-related problems and the APF-2000 solution includes professional sizing by qualified engineers who will analyse all the information required to accurately mitigate harmonics. This service is free-of-charge to the clients who wish to install harmonic solutions. Delta Energy Systems will guarantee compliance with meeting the requirements of IEEE Standards 519 – IEEE Recommended Practices and requirements for harmonic control in electrical systems. This solution will result in increased load efficiency and reduction in capital expenditure costs. Delta Energy Systems also will provide a standard 3 year warranty.

The relationship between harmonics and power factor?

There is however a relationship between these two power quality issues, see the graph below.


power quality and harmonics relationship

If you have 50% THDi (Total Harmonic Current Distortion Rate) in your electrical system the max power factor that can be achieved will be 0.8 (in this example). Harmonics are included in the calculation of the true power factor and therefore have a direct impact on its value. Passive capacitor banks only improve the displacement power factor (which is caused by inductive loads), but do not mitigate harmonic currents which is included in Irms (As shown in the above formulas). In order to achieve a power factor of above 0.8 in the example above, harmonic current (THDi%) must be lowered from its original 50% THDi value. Active Power Filters mitigate harmonics and correct power factor simultaneously to achieve the highest possible power factor.

What is Load Balancing?

An Active Power filter (APF2000) has the ability to balance the 3-phase load in real time, which is another advantage over passive technology. Many buildings and plants have single-phase or two-phase loads installed. This inherently causes unbalanced loading per phase on the three-phase supply and therefore results in the formation of reactive current in a negative sequence current. This negative sequence current can be thought of as reactive current in the electrical system, which reduces the overall capacity (i.e. transformers and cables). The Negative sequence currents can directly cause unbalanced voltages that trigger unstable currents in other loads. A voltage can be unbalanced by around 3% and is said to reduce the life of an AC motor by 10-15%. You subsequently reduce the life of non-linear loads and intermittent shutdown on devices.

Delta’s APF2000 has the ability to calculate the amount in the unbalanced load (negative sequence current) in order to inject the required current to each phase to form a balanced load.

Load Balancing


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