Electrical efficiency is a balance between two forces: inductive loads, such as motors and transformers, that make current lag voltage and create inefficiency; and capacitive loads, such as PFC capacitor banks, that make current lead. Power factor correction adds capacitive load to counteract the inductive lag, bringing the system to near-unity efficiency and avoiding demand penalties.
Every piece of equipment can be classified by the type of load it places on the supply. Understanding the difference between inductive and capacitive loads is the key to mastering system efficiency, which is measured by the power factor.
Inductive loads are the heavy lifters. They use magnetic fields to operate, and include electric motors and transformers. They are critical for driving mechanical processes, but they demand reactive power to sustain those magnetic fields.
Common examples include electric motors (especially at start-up), transformers, refrigeration compressors and fluorescent lighting ballasts.
Capacitive loads are the electrical energy savers. They store and release energy, and their main job in a commercial or industrial system is to improve power factor.
Examples include capacitor banks used for power factor correction, certain filtering components within variable speed drives, and specific electronic power supplies.
The art of power factor correction is balance: adding just enough capacitance to cancel the inductive lag, without overcorrecting. Get it right and the system draws close to only the real power it needs, cutting kVA demand and the charges that come with it.
Equipment that uses magnetic fields to operate, such as electric motors, transformers, refrigeration compressors and fluorescent lighting ballasts. They draw reactive power to sustain their magnetic fields, which makes current lag voltage.
The lag between current and voltage increases the apparent power (kVA) drawn from the utility, even though the useful power (kW) is unchanged. That artificially inflates maximum demand charges.
A load that stores and releases electrical energy and makes current lead voltage. In a commercial or industrial system, capacitor banks are added specifically to improve power factor by counteracting inductive lag.
By adding just enough capacitive reactive power to cancel the inductive reactive power, bringing current and voltage back into alignment and raising the power factor toward unity.