Cos Phi compensation: supporting cost saving and installation reliability

Cos Phi compensation supports cost saving

If you’re looking to improve the efficiency and reliability of your electrical installation, Cos Phi compensation will definitely be of interest. Installation of a Cos Phi capacitor bank offers numerous advantages, particularly in installations with inductive loads. Cos Phi compensation allows the installation’s available capacity to be used optimally. You can also prevent unnecessary energy losses and costs. Furthermore, Cos Phi compensation can make an essential contribution to CO2 reduction, which is beneficial to your profit margins as well as the environment.

Cos Phi compensation allows for improvement in electrical energy efficiency

Advantages of installing a Cos Phi capacitor bank

  • Better use of available installation capacity
  • Option to connect more loads within the same installation without requiring larger (or additional) transformers
  • Reduction of overload and overheating of installation and components (and associated risks)
  • Improvement of installation and component lifespan by reducing load and heat
  • Less energy losses and a lower energy bill
  • Sustainability through CO2reduction
  • Optimization of the overall Power Quality
  • Compensation for varying loads



Advantages of Cos Phi Compensation with capacitor bank


Cos Phi compensation is mainly beneficial to electrical installations with inductive linear loads (engines, transformers, reactors) and/or inductive non-linear loads (motor controllers, welding equipment, MRI scanner, rectifiers, UPS systems). To ensure this equipment works as intended, inductive power is required to maintain magnetism. However, this creates reactive power in the network. This reactive power, in turn, introduces an undesirable extra load for the electrical installation and components. By installing a Cos Phi capacitor bank, you can reduce reactive power, thereby improving energy efficiency and reducing costs.

Utilization Cos Phi Compensation

The functioning of a Cos Phi capacitor bank

Installing a Cos Phi capacitor bank reduces consumed reactive power. The capacitor bank provides capacitive power to compensate for the inductive power (reactive power). As a result, the reactive power does not pass through the entire installation. Energy losses in the installation are greatly reduced and energy efficiency is improved.

The right type and capacity

Different types of Cos Phi capacitor bank (regulated and fixed) are available, with dozens of different capacities. Each installation and situation requires correct analysis and calculation, in order to dimension the most suitable capacitor bank. HyTEPS has considerable knowledge and years of experience, allowing us to advise you. We supply a wide range of high-quality Cos Phi capacitor banks from several high-quality suppliers.

Commissioning Cos Phi capacitorbank

Controlled Cos Phi capacitor bank

Controlled Cos Phi capacitor banks are available in a wide range of capacities (kVAr). Depending on the value of the reactive power available and the desired or necessary compensation, the most suitable capacitor bank can be advised. The bank is built up in a number of steps. The regulated Cos Phi capacitor bank continually measures the required reactive power and switches capacity on or off with the available steps as required. Switching can be done by means of relays/contactors or thyristors. The greater the number of steps in a capacitor bank, the more accurately the reactive power can be compensated. This ensures optimal Cos Phi at all times. In electrical installations, in which harmonic pollution is present to a greater or lesser extent, the regulated capacitor bank is the most suitable type.

Relay switched capacitor bank

The relay switched capacitor bank responds to the inductive loads in the installation. When this capacitor bank detects a level of inductive power that is too high (causing the Cos Phi to deteriorate) the capacitor bank will respond by switching on a capacitor step by means of a relay. A relay-switched capacitor bank responds more slowly than a thyristor-switched capacitor bank.

Different combinations of steps are possible. It may be necessary to assign all steps an equal level of power, so that they alternately have the same duration of load. In this case, a capacitor step that has just been used may discharge while another step takes over the compensation. An additional advantage of this approach is the fact that compensation can be applied more rapidly.

There may also be a need for highly accurate compensation. In that case, capacitor steps may contain different values. By choosing the correct step, a capacitive load can be created that will be as close to the desired power as possible. This is very similar to paying an exact amount of money using coins of different value.

Thyristor controlled capacitor bank

A thyristor-controlled capacitor bank works in the same way as a relay switched capacitor bank. However, the thyristor-controlled capacitor bank has a much shorter response time. This extra speed is desirable when many rapid changes occur in the load, for example, in installations with welding equipment, cranes or short-term heavy inductive loads that regularly repeat their operation. Thyristor-controlled capacitor banks can switch on/off within milliseconds, perfectly compensating any highly inductive variance on the installation.

Thyristor-controlled cos phi compensation capacitor bank is ideal for installation with rapidly changing loads

Multiple installation options

Depending on the desired result and the connected load, there are two installation options: decentralized installation and centralized installation. In some cases a combination of decentralized and centralized compensation is required to achieve the optimal result.

Decentralized compensation

(at the end-user)

The Cos Phi capacitor bank is placed directly at the end-user.

Mainly used:

  • For heavy loads (load > 25kW) that are almost continuously in operation
  • To transport less apparent power through the power supply cable by reducing the reactive power
  • To reduce cable losses caused by reactive power

Centralized compensation

(at the main busbar)

In this case, the Cos Phi capacitor bank is installed at the main busbar. Central compensation generates more capacity from the transformer or main connection and prevents reactive power fines.

Combination of centralized and decentralized compensation

What does Cos Phi (Cos φ) mean?

Cos φ indicates the degree to which power is out of sync with voltage: the phase difference between the current and voltage. In other words, it indicates the amount of undesired power consumption in an installation. The smaller the Cos φ, the greater the degree to which the power is out of sync. The ratio between the active (actual) power and the apparent power is the cosine phi (Cos φ) or power factor. Cos φ is calculated as follows:

Cos Phi (at 50 Hz) =  Active power (kW) / Apparent power (kVA) = Power factor

Cos Phi diagram

In an ideal situation, Cos Phi equals 1. The more the value of Cos φ deviates from 1, the less efficiently energy can be transported through the installation. A lower Cos φ value yields higher losses and increased risk of dangerous situations. In these cases, Cos φ compensation provides numerous benefits.

A lower value for Cos φ is included in the grid code, from 0.85 for 50Hz installations to 50kV and from 0.80 for 50Hz installations of more than 50kV. If the Cos φ value is lower than the prescribed minimum, the grid operator will charge for this on the energy bill.


HyTEPS delivers more than only the product


HyTEPS not only supplies innovative high-quality products, but also offers added value in terms of measurements, analysis, advice, service and maintenance based on extensive knowledge and years of experience. As a result, we know for sure that the type of Cos Phi capacitor bank (or any of our other products) we recommend will be the best fitting solution for your specific situation and installation. After delivery and installation, we keep an eye on the installation. Commissioning is carried out by our highly qualified engineers. We also support you in the area of inspections, service and maintenance in order to guarantee the proper functioning of the solution we have provided.