Single phase 3-wire electronic electrical energy meter

Abstract

Metering kWh in a single phase, 3-wire, F.sub.L Hertz a.c. electrical system is accomplished by detecting the current flow in two lines of the three-wire system by means of a current transformer having two primary windings and a single secondary winding. The voltage in the system is detected by means of a potential transformer having the primary windings thereof connected across the load impedances and having the secondary thereof connected to a pulse width amplitude modulated multiplier. The multiplier derives a signal which is proportional to the current in the system and the detected voltage across the load impedances thereof. The output of the multiplier is converted to a d.c. voltage which is proportional to the total average power consumed by each of the load impedances with the d.c. average power voltage being converted to a pulse train by an analog-to-pulse rate converter. Thus the output of the analog-to-pulse rate converter is a series of output pulse signals having a variable signal repetition rate f proportional to the average power with each pulse signal representing a constant or quantized amount of electrical energy. A counter or register performs conventional accumulation storage and display functions in response to the series of output pulses delivered thereto from the analog to pulse rate converter.

Dependencies are inferred from the claim text.