Electricity: motive power systems – Induction motor systems – Power-factor control
Patent
1989-01-30
1991-01-01
Shoop, Jr., William M.
Electricity: motive power systems
Induction motor systems
Power-factor control
318721, 318722, 318800, 318808, 318809, 388812, 388903, H02P 528
Patent
active
049821474
ABSTRACT:
A device and associated method to control the electromechanical energy conversion process of a variable speed drive utilizing a doubly fed machine, which provides the mechanical energy as demanded by some mechanical load. Alternatively, a device and associated method is provided for a synchronous motor. The terminals of either the stator or rotor winding of the doubly fed machine are directly connected to a polyphase AC power grid of a certain grid frequency. The device establishes through electronic control a stable operation of the drive at a desired power factor at the terminals of these windings, irrespective of varying load conditions. This capability is provided without the need for computing or sensing this desired power factor and the subsequent feedback of its deviation from the desired value through a properly designed regulator. All signal processing as required can be conveniently and reliably implemented; only the easily accessible quantities of the stator voltage and real power supplied to the motor are sensed and subjected to simple algebraic manipulations. Torque speed characteristics produced by the drive are compatible with any demanded load condition within design limits. These flexibilities are retained along with the capability of electronically adjusting the drive speed without the need for detecting the mechanical load condition.
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Martin David
Shoop Jr. William M.
State of Oregon Acting By and Through the State Board of Higher
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