Choosing the Right Capacitor Bank for Power Factor Correction!

Choosing the Right Capacitor Bank for Power Factor Correction!

What is capacitor bank? A capacitor bank consists of several capacitors. All these capacitors are of the same rating and are connected in series or parallel sequence. It stores electrical energy in an electric power system. These devices store electric charge by creating an electric field between two metal plates. The metal plates in the capacitor banks are separated by an insulating material. So, what are capacitor banks used for? Usually, they are used for power factor correction, harmonic filtering, voltage regulation and transient suppression.

To know more about these banks and how to choose the right one, continue reading.

What are Capacitor Banks Used for?

The following are the most common uses of capacitor banks.

  • They are primarily used to increase the quality of the electrical supply. They also help enhance the efficiency of power systems. 
  • Capacitor banks are usually used for AC power supply correction in industries that use transformers and electric motors. 
  • They help solve power lag in systems at less cost by alterations in the power grid. 
  • Capacitor banks assist in decreasing the phase difference between the voltage and current. 
  • They are used in Marx generators, radars, fusion research, nuclear weapons, detonators, pulsed lasers, coilguns and electromagnetic railguns. 

How to Calculate Capacitor Bank?

For single-phase AC circuit:

First, convert the given power factors into angles. Use the following formula for it. 

CosØ = power factor

Ø = Cos-1 (power factor)

Now, calculate the angle of the old and new power factor required.

Ø1 = Cos-1 (old power factor)

Ø2 = Cos-1 (new power factor)

The next step involves calculating the required capacitance reactive power.

Qc = P(tanØ1-tanØ2)

For calculating capacitance, use the following formula.

C = Qc/V2*2*pi*f

For 3-phase AC circuits:

First, convert the given power factors into angles:

CosØ = power factor

Ø = Cos-1 (power factor)

Now, calculate the angle of the old and new power factor required.

Ø1 = Cos-1 (old power factor)

Ø2 = Cos-1 (new power factor)

Calculate the required capacitance reactive power:

Qc =P(tanØ1-tanØ2)

For the capacitance:

If line-to-line voltage is given, you must convert it using the following formula. 

Vph = Vll/ 1.73

Calculation capacitance with the formula:

C = Qc/ Vph2*2*pi*f

How Many Types of Capacitor Banks are Available?

Following are the three types of capacitor banks. 

Internally Fused Capacitor Banks

Internally fused capacitor banks are made with a certain setup which combines capacitor elements in parallel arrangements and series based on their rating. Every capacitor element is individually protected by its own fuse unit. As the name implies, both capacitor components, as well as the fuse units, are housed in the very same enclosure. The unique capacitor components in these banks are fairly small, dependent on their ratings.

If capacitor elements break, the functioning of the capacitor bank isn't affected. This particular redundancy allows the bank to keep working even if one or maybe more capacitor elements are of service. Among the crucial advantages of internally fused capacitor banks are their ease of setup and low maintenance requirements. 

Externally Fused Capacitor Banks

In an externally fused capacitor bank, each capacitor unit is shielded by a fuse situated outside of the capacitor casing. If a fault happens in virtually any capacitor unit, the outside fuse blows, isolating the defective capacitor out of the system. This particular style enables the capacitor bank to keep on working with no interruption despite specific unit failures.

In this particular configuration, capacitor units are generally connected in parallel inside each stage of the bank. If one capacitor unit fails, the general functionality of the bank is just minimally impacted. Nevertheless, the loss of a capacitor product in a single stage is able to result in a minimal decrease in capacitance for that stage, possibly affecting the balance between the 3 phases.

Fuse Less Capacitor Banks

In a fuseless capacitor bank, capacitor strings are created by linking many capacitor units in series. These strings are now connected in parallel to produce a capacitor bank for every stage. To produce an entire three-phase capacitor bank, three such banks are attached in a star or even delta configuration.

In this particular kind of setup, there's no external or internal fusing to safeguard the capacitor strings. As an outcome, if a string fails because of a short circuit or maybe some other fault, the flow of current through the string is still mostly unaffected. This is because the sequence arrangement of capacitors ensures the general course stays intact regardless of the failure of specific units.

Selecting the Proper Capacitor Bank

The key to selecting the proper capacitor bank is to use the Power factor correction formula and calculate the right size. Also, you must follow the entire process of calculating capacitor bank size, as explained above in this blog. Following a step-by-step procedure will ensure you invest in the right device. 


In the End

The crucial role of capacitor banks can never be neglected. However, to ensure you relish the functionality of these devices, you must pick the most suitable capacitor bank. Follow this guide to calculate the right size and consider other crucial factors to find the bank that fulfils all your requirements. Also, no matter what type of capacitor bank you need, you can conveniently shop for them from the Schneider Electric e-shop

Frequently Asked Questions

Q1. What is Capacitor Bank?

Ans: A capacitor bank is a device consisting of several capacitors. These capacitors are of the same rating. They might be connected in series or parallel and store electrical energy in them. 

Q2. What are the different types of capacitor bank?

Ans: Capacitor banks are of the following three types.

  • Internally Fused 
  • Externally Fused
  • Fuse less