Service
Power Factor Correction
Client
Fasque Timber Products
Industry
Sawmill
Location
Fordoun
Introduction
The purpose of a power factor correction unit is to improve the efficiency of an electrical system. When electrical devices like motors, heaters, and lighting are used they require power that is supplied by the grid and/or a generator. Some of these devices can cause the electrical system to work less efficiently, which can result in wasted energy, higher electricity bills, and increased strain on the grid/generator.
A power factor correction unit helps to address this problem by optimising the way electricity is used in the electrical system. It does this by increasing the active power and reducing the reactive power, which helps to reduce energy waste and lower electricity bills.
Active power (also known as real power) is the power that is actually consumed by an electrical circuit and is measured in watts (W). Apparent power is the total power delivered to a circuit, and is the product of the voltage and current and is measured in volt-amperes (VA).
Reactive power, on the other hand, is a component of apparent power that does not result in actual energy consumption. It is the power that flows back and forth between the reactive elements of an electrical circuit (such as inductors and capacitors) and the source of the power, without actually being consumed. Reactive power is measured in units of volt-amperes reactive (VAR).
In the case of a sawmill, heavy usage of motors causes a high inductive load. This means the voltage and current sine waves from an alternating current (AC) supply are out of sync. This causes a reactive power (VAR) which is waste energy. The motors still require the same amount of active power (W) to function so a higher amount of apparent power (VA) is drawn in order to meet the required active power (W).
An inductive load causes the power factor to lag and a capacitive load causes the power factor to lead.
An inductive load can be countered with capacitors and a capacitive load can be countered with inductors. The power factor unit will monitor the power delivered on site and introduce capacitors/inductors as is necessary to achieve a unity power factor (1).
Post-Commissioning
The data below was taken after the power factor correction unit was commissioned. All three phases were analysed over the course of an hour during normal operation at the sawmill.
With the power factor correction unit connecting capacitors automatically to counter the inductive load from the site a significant increase in power factor was evident.
Power factor increased from 0.41 – 0.45 to 0.97 – 0.99. The active power required by the site was almost identical at around 60.1kW – 61.1kW. With the power factor correction unit functioning, apparent and reactive power both reduced significantly. Apparent power generated was reduced to 61.7kVA – 62.5kVA and reactive power lost was reduced to 12kVAR – 13.5kVAR.
Pre-Commissioning
The data below was taken before the power factor correction unit was commissioned. All three phases were analysed over the course of an hour during normal operation at the sawmill.
As seen below, the apparent power generated varies between 126.8kVA – 132.3kVA, active power consumed by the site sits between 55.6kW – 56.4kW and reactive power lost is between 113.6kVAR – 120.1kVAR.
The high apparent and reactive power is caused by the low power factor which stayed between 0.41 – 0.45.
Due to the low power factor the generator has to generate around 73kVA more apparent power to meet the active power (kW) required by the site demand.
Savings Comparison
With the installation of power factor correction, we estimate there will be a payback period of around 1.57 years with savings at around £6.3k per year.
Comparison below with pre-commissioning results in RED and post-commissioning results in
GREEN.
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