Patent ID: 9628016
Date: 2017-04-18
CPC Classifications: E21B,F04B,H02J,H02P

Claim:
1. A system comprising: an AC motor having an input and an output adapted to be connected to a changing load; a variable frequency AC drive having an input adapted to be electrically coupled to an electric power grid and an output electrically connected to the input of the AC electric motor; said variable frequency AC drive including an active converter having a predetermined maximum apparent power capacity and an inverter connected to the converter and an output connected to the AC motor to provide reactive power to the motor; a programmed controller coupled to said converter to regulate reactive power generation and consumption of the variable frequency AC drive so that said drive produces reactive power when said converter is utilizing less than said converter's maximum apparent power capacity, said reactive power being generated without compromising the ability of the drive to provide real power as demanded by said load, said reactive power being fed to the power grid; wherein the programmed controller has a selectable mode control that establishes which one or more than one of a plurality of control strategies is employed, said strategies governing the combination of reactive power and real power to avoid the apparent power exceeding the maximum apparent power capacity of the active converter; wherein the programmed control strategies include (1) a first control strategy where the load on the motor changes slowly, (2) a second control strategy where the load changes rapidly, and (3) a third control strategy where the load is cyclic; and a device that monitors current and voltage from the power grid and generates a reference signal corresponding to a power factor for a system in which the apparatus is connected, and the controller is programmed to respond to said signal.