Energy Measurement in Split-Phase Systems Using 78M6612


This document discusses energy measurement in split-phase systems. A split-phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial (up to about 100kVA) applications. A 3-wire system, using a distribution transformer with a single-phase input (primary) winding, is common in countries with a standard phase-neutral voltage of 120V.

This article analyzes three different load cases:

  • Line1/Neutral + Line2/Neutral: balanced load (case 1)
  • Line1/Neutral + No load on Line2: unbalanced load (case 2)
  • Line1/Neutral + Line2/Neutral + Line1/Line2: unbalanced load (case 3)

A firmware load for the 78M6612 energy-measurement IC was developed to implement split-phase measurement for two independent phases with a phase offset of 120° or 180°. It implements 4 channels (2I and 2V) and measures RMS for each channel as well as power for two phases. Two voltage dividers and two current transformers as sensors are required. Read full article.