Describes how the ADE7758 chip calculates power factor, and how to detect phase dropouts that cause errors in power factor calculation
The ADE7758 is a polyphase, multifunction energy metering IC that performs kWh, kVAh, kVARh, and rms current and rms voltage measurements. This document describes how phase dropout affects VAR calculation and provides solutions to detect and handle it.
Two solutions are presented for phase dropout detection. The first involves using a combination of zero-crossing timeout interrupts and voltage SAG interrupts to promptly identify the dropped phase. The second method suggests monitoring voltage rms values, though this is noted as not recommended due to higher system resource usage and power consumption.
If the phase used for frequency measurement drops out, it can induce an error in the reactive power calculation of the other phases.
The corresponding zero-crossing timeout detection bit is set in the status register after 384/CLKIN x ZXTOUT seconds.
A voltage SAG event is recorded when the absolute value of the line voltage drops below a set peak value for nine half cycles.