US Patent 7629705 Method and apparatus for operating electrical machines

A method for operating an electrical machine includes coupling the electrical machine to an electric power system such that the electric power system is configured to transmit at least one phase of electric power to and from the electrical machine. The method also includes configuring the electrical machine such that the electrical machine remains electrically connected to the electric power system during and subsequent to a voltage amplitude of the electric power system operating outside of a predetermined range for an undetermined period of time.