Resources Contact Us Home
Apparatus and method for measuring power factor and torque on the output of variable frequency drives

Image Number 3 for United States Patent #5003252.

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.

  Recently Added Patents
Method and system for placing an emergency call
Selecting one of a plurality of print modes based on pixel coverage of a document
Vacuum cleaner filter adapter ring
Epoxy composition for encapsulating an optical semiconductor element
Scaleable status tracking of multiple assist hardware threads
Method for production of fermentable sugars from biomass
Package for a medicinal product
  Randomly Featured Patents
Method for producing an article having an elastic bonded between two webs
Manual motion control override apparatus
Bland whey product and process of preparation
Method and a catalyst for the oxidation of a conjugated diolefin
Antifungal bicyclic hetero ring compounds
Process for preparing styrenic resin
Tool coupler and extender mechanism
Touch-sensitive operating panel for cooking zones
Integrating social contact identifiers into wagering games
Memory system with multiple addressing and control busses