Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Patent
1989-08-16
1991-03-26
Karlsen, Ernest F.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
324 83R, G01R 3102, G01R 2500
Patent
active
050032526
ABSTRACT:
An apparatus and method for sensing power factor and torque on the output of a variable frequency machine is disclosed. Initially, power is sensed in each phase of the three-phase machine by utilizing Hall generators for multiplying the phase current flowing through each phase by a current proportional to a phase voltage for each phase. The products are then summed to obtain a reading of the instantaneous power drawn by the three phase machine. The AC component is filtered out of the summed signal using a multistage filter which allows for maintaining a fast response time with low ripple. This output is divided by the speed of the machine and multiplied by a constant to result in a signal representing torque. For measuring power factor, power signal sensed in each phase is applied to a DC blocking capacitor, effectively separating the AC envelope proportional to voltage times current. The three signals are applied to absolute value amplifiers and summed to provide a signal yielding total power. The instantaneous power is then divided by this signal to provide power factor.
REFERENCES:
patent: 4442393 (1984-04-01), Abbondanti
patent: 4724373 (1988-02-01), Lipo
patent: 4764720 (1988-08-01), Nystrom
Karlsen Ernest F.
Load Controls Incorporated
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