“Active power” and “reactive power” are critical terms in electrical engineering. Active power, measured in watts (W) or kilowatts (kW), represents the actual power consumed by electrical equipment to perform useful work, such as running motors, lighting, and heating. Reactive power, measured in volt-amperes reactive (VAR), represents the power that oscillates between the source and the load, necessary for creating magnetic and electric fields in inductive and capacitive components.

“Power factor” expresses the ratio between active power and apparent power, where apparent power is the combination of active power and reactive power, measured in volt-amperes (VA). The power factor is a dimensionless number ranging from 0 to 1, typically expressed as a percentage. A power factor of 1, or 100%, indicates that all the supplied power is being effectively converted into useful work.

When designing an electrical circuit or feeder for loads in watts or kilowatts, it’s imperative to know the power factor of the load. A low power factor indicates inefficient utilization of electrical power, leading to higher current flow for a given amount of useful power. This inefficiency can result in increased energy losses in the distribution system and higher electricity costs.

Even though electric utilities measure customers’ electricity consumption in active power (kilowatts, e.g.), they assess a penalty to customers whose systems operate at a low power factor, typically below 90%. This penalty is imposed because low power factor systems require utilities to generate and deliver more apparent power to supply the same amount of active power, straining the electrical infrastructure and increasing operational costs. Improving the power factor can lead to reduced energy losses, lower electricity bills, and enhanced capacity of the electrical system.

Now let me use the following “beer in a jar” analogy to visualize and understand the relationship between active power, reactive power, and apparent power, and emphasize the importance of maintaining a high power factor in electrical systems for efficient energy usage.

1. Real Power (Active Power):
   • Depicted as: The actual beer in the glass.
   • Measured in: Kilowatts (kW).
   • Explanation: This represents the useful power that performs actual work, like lighting, heating, or running motors.

2. Reactive Power:
   • Depicted as: The foam on top of the beer.
   • Measured in: Kilovolt-amperes reactive (kVAR).
   • Explanation: This represents the power used to maintain the electric and magnetic fields in inductive and capacitive equipment. It does not perform any useful work but is necessary for the functioning of AC systems.

3. Apparent Power:
   • Depicted as: The entire content of the glass (beer plus foam).
   • Measured in: Kilovolt-amperes (kVA).
   • Explanation: This is the combination of real power and reactive power. It represents the total power that must be supplied by the source to meet the demands of the load.

Power Factor:

• Formula: Power Factor = Real Power (kW) / Apparent Power (kVA)
• Depiction: The ratio of beer to the entire glass capacity.
• Explanation: The power factor is a measure of how effectively the electrical power is being used. A higher power factor indicates more efficient utilization of electrical power. A power factor of 1 (or 100%) means all the power is being effectively converted into useful work, whereas a lower power factor indicates inefficiencies due to the presence of reactive power.

Key Points:

• High Power Factor: More beer (real power) compared to the foam (reactive power), indicating efficient use of electrical power.
• Low Power Factor: More foam compared to beer, indicating inefficiencies and the need for the electrical source to supply more apparent power to achieve the same amount of real power.

Key Takeaways:

• Designing Electrical Circuits: Knowing the power factor is crucial for designing efficient electrical circuits and feeders.
• Electric Utility Penalties: Utilities often penalize customers with low power factors because it indicates that the customer’s system requires more apparent power, thereby straining the utility’s capacity and increasing operational costs.

Enjoyed our beer analogy? Stay tuned for more unique perspectives and expert insights. Follow us on social: LinkedIn, X, and Facebook for regular updates. Join our email list to get the latest content delivered straight to your inbox. Cheers to staying informed!