Power Factor and Three Phase Power Loggers

Use this guide when you need to understand power factor, kW, kVA, kVAR, peak demand or three-phase load behaviour from recorded proof.

Power factor investigations need voltage and current measured together. Current-only or voltage-only loggers can answer narrower questions, but they cannot calculate real power, reactive power, apparent power or power factor by themselves.

When to investigate power factor

• You need to check whether poor power factor is increasing demand, losses or supply capacity requirements.
• You are assessing whether power factor correction equipment is needed, correctly sized or operating as expected.
• You need proof of kW, kVA, kVAR, power factor and peak demand over a normal operating period.
• You want to compare three-phase load behaviour before and after correction, maintenance or process changes.
• You need to understand phase loading as well as total site demand.

What to measure

• Three-phase voltage and current at the same time.
• kW, kVA and kVAR.
• Power factor over time.
• Peak demand and load profile.
• Phase loading, imbalance and operating patterns.

Recommended logger

Quick comparison

Use this table as a quick route from the investigation type to the most likely logger.

How to choose

• Choose EC-7VAR-RS when the investigation needs voltage, current, power, energy and power factor together.
• Consider a current logger only when current trend or load profile is enough and calculated power values are not required.
• Consider a voltage logger only when the question is supply voltage, voltage variation or interruption timing rather than power factor.

Typical investigation workflow

• Define the measurement point, such as an incoming supply, distribution board or major load.
• Record long enough to include representative operation, including shifts, process cycles, start-up periods or high-demand periods.
• Review kW, kVA, kVAR, power factor, peak demand and phase loading together.
• Compare the data with billing, plant operation, correction equipment status or planned capacity changes.
• Use the results to support power factor correction decisions, capacity planning or energy-audit recommendations.

Useful reading

• Power Factor Correction
• Power Factor Correction article
• Energy Auditing
• Saving Energy in Industry
• Recording Electrical Energy Use is Easy
• Products by Use: power factor and three-phase power analysis

Need help choosing?

If you are not sure whether you need power factor measurement or a simpler current/voltage logger, contact us with the supply type, load type, measurement point and what decision the data needs to support.