Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Phase comparison
Patent
1979-10-02
1982-03-23
Tokar, Michael J.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Phase comparison
324 83A, 324127, G01R 2500
Patent
active
043215297
ABSTRACT:
A power factor metering device. The power factor metering device includes a novel electronic circuit for deriving the power factor from a detected voltage and current. The device includes a current clamp that may be clamped onto any conductor of a three-phase or single-phase circuit. Voltage clips are used to detect the circuit's voltage. The current clamp induces a voltage that lags the detected current by 90 electrical degrees. An amplifier stage is coupled to the induced voltage through a low input variable resistance so that the input voltage to the amplifier stage may be adjusted to correct for errors induced in the phase relationship between the detected voltage and current. The output from the amplifier stage is input into a zero crossing detector stage that changes its output state each time the output of the amplifier stage passes through zero. The output of the zero crossing detector stage is applied to one side of a pair of EXCLUSIVE-OR gates, and is also applied to one of the inputs of a bistable multivibrator. The voltage detected by the voltage clips is stepped down by a transformer and is input to a second zero crossing detector stage. The output from the second zero crossing detector stage provides the other input to the EXCLUSIVE-OR gates and the bistable multivibrator. The output of each EXCLUSIVE-OR gate is directly proportional to the phase angle between the detected voltage and current. The outputs from the two EXCLUSIVE-OR gates are amplified and are used to drive a continuous recording device and an instantaneous meter which each display the magnitude of the power factor derived from the detected current and voltage. The output from the bistable multivibrator is used to determine whether the current signal leads or lags the voltage signal.
REFERENCES:
patent: 3052844 (1962-09-01), Varterasian
patent: 3986116 (1976-10-01), Smith
Ardin Dennis B.
Simmonds Charles W.
Nydegger Rick D.
Tokar Michael J.
Workman H. Ross
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