Need for Power Factor Correction
Electricity is the lifeline of modern life. It is powering everything from household appliances to industrial machinery. We are familiar with the basics of electricity—voltage, current, and power—there’s one more important aspect that often goes unnoticed: power factor. A good power factor can save money, improve efficiency, and reduce the strain on electrical systems.
What is Power Factor?
- Power factor angle(θ) is the phase difference between the supply voltage and the supply current. The greater the difference, the lower the power factor. The cosine of the power factor angle is the power factor. (cosθ)
- Inductive loads are a major contributor to decreasing power factor. Lightly loaded induction motors and lightly loaded transformers are one of the few reasons.
- Power factor (PF) indicates how effectively electrical power is being used. It’s the ratio of real power (kW), which performs useful work, to apparent power (kVA), the total power supplied by the utility. Power factor can only range from 0 to 1.
- PF = 1: All the power is being used effectively.
- PF < 1: Some power is wasted, usually due to reactive loads like motors, transformers, or fluorescent lighting.
Why Low Power Factor is a Problem?
A low power factor isn’t just a technicality—it has real-world implications:
- Increased Electricity Bills
Utilities charge for apparent power (kVA), not just the actual work done. If your PF is low, you’re paying for energy that isn’t being used efficiently. - Overloaded Electrical Systems
Low PF increases current in the electrical system, which means wires, transformers, and switchgear must carry more current than necessary. This can cause overheating and reduce the equipment’s lifespan. - Reduced Capacity
In industrial settings, low power factor limits the capacity of generators and transformers, meaning less actual output can be achieved without upgrading the conductor size in the equipment. - Energy Losses
Extra current caused by low PF results in higher losses in cables and other electrical components, reducing overall system efficiency.
Power Factor Correction
Power factor correction (PFC) improves efficiency by reducing the phase difference between voltage and current. As low power factor is introduced because of inductive loads, adding capacitor banks in the system is an obvious solution. Along with capacitor banks, we can introduce synchronous condensers in the system.
Once the capacitor bank is added to the circuit, inductive reactive power reduces. Thereby, the phase difference between the supply voltage and supply current is reduced. Note that θ2 is less than θ1.
How Power Factor Correction Helps?
The phase difference between the supply voltage and supply current is reduced. Power factor correction (PFC) improves efficiency by reducing the phase difference between voltage and current. It makes sure that useful power remains the same as earlier, but reactive power is reduced. So overall efficiency increases.
- Lower electricity bills: Less wasted power means lower utility charges.
- Reduced current draw: Minimises losses and prevents overheating.
- Increased system capacity: Free up space in transformers and generators for more real work.
- Improved voltage stability: Provides a more reliable and stable supply, especially for sensitive equipment.
Practical Examples
- Industrial Motors: Motors often cause a lagging power factor because they draw reactive power. Adding capacitor banks near motor loads can correct PF.
- Commercial Buildings: Fluorescent lights and HVAC systems introduce reactive loads. PFC reduces unnecessary strain on the electrical system.
Let’s dig in and see how our Ausinet Power Factor Correction Calculator can help you calculate the required capacitor size for the power factor correction.
Required Inputs
Power factor correction involves reducing reactive power (Q) by adding capacitive reactance, thereby improving the power factor from Cos θ₁ (original) to Cos θ₂ (target).
| Input Field | Description |
| Frequency (Hz) | System frequency (typically 50 Hz in Australia) |
| Voltage (V) | Line voltage of the system |
| One of the following: | |
| – Original Apparent Power (S) | Total power (VA) before correction |
| – Real Power (P) | Total Active Power (VA cosθ) |
| – Reactive Power (Q) | Inductive reactive power before correction (VA sinθ) |
| – Rectified Apparent Power (VA) | Apparent power after correction (S), if known |
| Enter both: | |
| Cos θ₁ | Original power factor (before correction) |
| Cos θ₂ | Target power factor (after correction) |
| Click on ‘Calculate’ to see the results | |