What Is Power Factor in Diesel Generator?

If you are looking for a diesel generator (DG) on the Internet, you may find power factor in the technical specifications of different diesel generators provided by manufacturers. What does it mean? In fact, power factor in a generator measures how efficiently this unit uses its energy. It is one of the key considerations when you are investing in an electric power generator. Read on and learn more about power factor.

What is the power factor in a generator?

Power factor or PF is the ratio of actual power (kW) to apparent power (kVA), which is typically expressed as a decimal or percentage. It essentially measures the efficiency with which the generator uses its energy. It’s worth noting that power factor is created by load, not by the generator. It is essentially calculated on the basis of the devices connected to the generator. Most of diesel generator manufacturers mention 0.8 or 80% as the rated power factor of DG, meaning these loads can use 80% of the generator’s power supply. Power factor is measured as a unitless quantity and the number is usually accompanied by leading or lagging.

Typically, data such as the kW, kVA and PF values will be displayed on a diesel generator’s nameplate. First of all, you need to understand the difference between active power, reactive power and apparent power. Active power is used to measure the real electric power provided by the generator, and it is measured in kW (kiloWatt). Reactive power is the used power that creates and maintains the electromagnetic fields of the inductive loads (engines, converters, ballast for discharge lamps, induction ovens). It’s measured in kVAr (kiloVolt Ampere reactive). Apparent power is a combination of both reactive power and active power. It is measured in kVA (kiloVolt Ampere). Apparent power is the product of a circuit’s voltage and current, without reference to phase angle.

As a rule, active power is a result of resistive components and reactive power is a result of capacitive and inductive components. Apparent power is a function of a circuit’s total impedance. Power factor is caused by kVArs. When a generator is producing (positive) kVArs the load is inductive, such as a motor, and thus the current is lagging the voltage. When a generator is absorbing (negative) kVArs the load is capacitive such as fluorescent lighting and long cable runs, and thus the current is leading the voltage. If the generator is feeding a purely resistive load, such as a heating element, there are no kVArs, and the PF is 1, also known as unity. This is when real power is equal to apparent power.

How to calculate power factor of diesel generator?

As mentioned above, power factor is the ratio of actual power or real power to apparent power. You can use the following formula to calculate the power factor:

PF = kW / kVA

Where:

PF = power factor

kW = real power (or actual power) measured in kilowatts

kVA = apparent power, measured in kilovolt-amperes

As the formula implies, the higher the PF, the more efficient is the diesel generator in using its energy. For the purely resistive circuit, the power factor is 1 (perfect), because the reactive power equals zero. In most cases, single-phase generators are known to have a power factor of 1.0 and three-phase diesel generators usually have a power rating of 0.8. Single-phase gensets usually do not go above 40 kW, which are commonly used in residential environments. 3-Phase diesel generators are mainly for larger industrial power generation.

Why is the power factor important?

Power Factor is a measure of how effectively incoming power is used in your electrical system (energy efficiency). Most of diesel generator manufacturers mention 0.8 as the rated power factor of DG. As a DG cannot absorb reactive energy the power factor must stay in the lagging region. So the power factor has to be kept between 0.8 and 1.0.

Low or poor power factor indicates that the energy efficiency is low, which means that more current is required to perform the same amount of work, resulting in a waste of money for the end user. A low power factor can cause problems like voltage drops and increased current in the system, which can lead to reduced system performance. Additionally, large currents at a low power factor can also cause voltage losses in the alternator, which in turn can lead to reduced loading handling capacity. 

How to improve power factor? Generally, many factors can contribute to a low power factor, such as inductive loads, unbalanced loads and improperly sized power factor correction capacities. You can improve power factor in a few ways, such as adding power factor correction capacitors, optimizing generator excitation, using electronic devices, using synchronous condensers, optimizing the load and using power factor controller. These can help you reduce your electricity costs.

All in all, power factor is a key consideration that should note be overlooked when you purchase a diesel generator. If you’re still unsure how to choose the right generator, contact us today. Dingbo Power is a professional diesel generator manufacturer with more than 17 years’ experience. We can help you find the generator set that best suits your needs. Don’t hesitate to reach out for any further information or assistance regarding to diesel generator technical specifications.