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 efficient DRX operation during handover in LTE
Financial transaction cards
Systems and methods for identifying similar documents
Method and apparatus for connecting signal lines of multiple layers to certain contacts while preventing connections with other contacts
Clusterin antisense therapy for treatment of cancer
Grounding fitting
Systems and methods of using dynamic data for wear leveling in solid-state devices
  Randomly Featured Patents
Intermediates useful in preparing certain pyrrolotriazine compounds and process for making such intermediates
Shoe cartridge cushioning system
Resin composition comprising unsaturated dicarboxylic acid anhydride polymer, polycarbonate resin and modified olefin polymer
Belt lock with a switch arrangement for detection of the locking status
Connector for attaching a cable to a printed circuit board
Optical image detecting device with optical image differential capability
Solder-bearing components and method of retaining a solder mass therein
Lubricating oil containing dispersant viscosity index improver
Side tear shaped vacuum pouch
Efficient method and apparatus for access and storage of compressed data