Why should you care about Power Factor Power Factor ?
- Truewatts
- Feb 10
- 4 min read
Updated: Jul 21
When it comes to electrical systems, Power Factor (PF) is one of the key indicators used to measure how efficiently energy is being utilized. PF tells us how effectively electrical equipment or the overall system uses the power it receives.
When the Power Factor is close to 1.0 (or 100%), it means the electrical system is operating at maximum efficiency with minimal energy loss. However, when the Power Factor drops, it negatively impacts energy efficiency, which may lead to power losses and increased long-term operational costs.
A low Power Factor reduces system efficiency in several ways, including:
1. Increased Current
When the Power Factor is low, the system requires more current to deliver the same amount of real power. This is because reactive power causes the apparent power to increase.
Higher current results in energy losses (I²R losses) in cables and electrical equipment, reducing the overall energy efficiency of the system.
Additionally, increased current may force electrical components such as transformers or wiring to carry higher loads, leading to excessive heat and accelerated wear of the equipment.
2. Voltage Drop
When a system has a low Power Factor, it causes more current to flow through the wires, which leads to voltage drops along the electrical lines.
This voltage drop can cause electrical equipment to operate below optimal performance. For example, motors or machinery may not function as designed, resulting in system instability and reduced efficiency.
3. Increased Burden on Electricity Providers
When the Power Factor is low, electricity providers must generate more power to meet demand — even though part of that energy (Reactive Power) does not perform actual work. However, it still needs to be supplied to support the system load.
As a result, the overall cost of the electrical system increases for both electricity users and providers.
4. Increased Costs
In some cases, electricity providers may impose Power Factor penalty charges to help reduce the overall cost of the electrical system and encourage more efficient electricity usage.
In this article, we will discuss Power Factor and divide it into two main categories: Displacement Power Factor (DPF) and True Power Factor (TPF), along with an explanation of why both types deserve our attention.
1. Displacement Power Factor (DPF)
Displacement Power Factor (DPF) refers to the power factor that reflects the phase relationship between voltage and current, specifically the phase shift. It is measured by the phase angle of the current that either lags or leads the system voltage. In electrical systems using linear loads—such as motors or electrical devices that do not cause waveform distortion—DPF is primarily related to phase shift and can be easily calculated.
2. True Power Factor (TPF)
True Power Factor (TPF) is the power factor that includes both phase shift and current waveform distortion. Distortion typically arises from non-linear loads, such as electronic equipment, computers, or variable speed drives (VSDs), which generate harmonics in the current and distort the waveform.
Why Should We Care About DPF?
🔹 Reducing Power Losses:When current is out of phase with voltage, it generates reactive power, which cannot be used to perform real work.
DPF reflects the efficiency of delivering real power in a system. The closer DPF is to 1.0, the more effectively the system converts supplied energy into useful work. A low DPF indicates poor energy usage efficiency, leading to unnecessary power losses in the system.
🔹 Improving System Efficiency:Improving the DPF (bringing it closer to 1.0)—often by using capacitor banks—can reduce energy losses and make the overall power system more efficient.
Why Should We Care About True Power Factor (TPF)?
🔹 Reducing the Impact of Harmonics:Harmonics generated by electronic devices or non-linear loads (e.g., VSDs, computers, or industrial equipment) affect both Displacement Power Factor (DPF) and True Power Factor (TPF). These harmonics distort the current waveform, which causes the TPF to drop—resulting in increased energy losses, even when the DPF may still appear acceptable.
🔹 Improving System Efficiency in Harmonic-Rich Environments:In systems with high harmonic distortion, it is necessary to install harmonic filters to improve both DPF and TPF. These filters help reduce current waveform distortion and enhance overall energy efficiency.
DPF vs. TPF: When Should You Pay Attention to Both?
If You Have Linear Loads:If your electrical system primarily uses linear loads—such as motors or standard electrical appliances that do not generate harmonics—then improving the Displacement Power Factor (DPF) is usually sufficient. In this case, the phase angle between voltage and current is the key factor affecting efficiency.
If You Have Non-Linear Loads:If your system includes non-linear loads such as electronic devices, computers, Variable Speed Drives (VSDs), or power supplies with signal conversion that generate harmonics, then monitoring the True Power Factor (TPF) becomes essential. TPF helps provide a more complete picture of energy losses due to both waveform distortion and phase shift.
From the real example in the image below, it is clearly observed that in a system with high harmonics, the values of TPF and DPF differ significantly.
Summary
Power Factor (PF) is a key factor in measuring the energy efficiency of an electrical system. Calculating PF helps us understand actual energy usage, particularly through the two main components: Displacement Power Factor (DPF) and True Power Factor (TPF), each of which plays a different role depending on the type of load in the system.
Focusing on DPF is appropriate for systems with linear loads and minimal harmonics, while TPF becomes more important in systems with non-linear loads, which may cause current waveform distortion. Understanding both DPF and TPF allows us to optimize energy usage and effectively reduce power losses within the electrical system.
If you're interested in having Truewatts conduct a system measurement at your facility, please contact us at: Info@Truewatts.co.th
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