Patent ID: 7877170

Claim:
A method for controlling the points at which an induction machine is configured to be connected to a power grid comprising the steps of: measuring the frequency of remanent voltage generated at the start up of the induction machine corresponding to rotation speed thereof and comparing the measured frequency with a preset rotation speed threshold; and connecting the induction machine to the power grid when said frequency of the remanent voltage is greater than the preset rotation speed threshold equal at least to a value corresponding to a desired grid-synchronous speed; monitoring the power being generated by said induction machine and disconnecting said induction machine from the power grid if a disconnection condition occurs; instituting a dead time lockout condition following a disconnection to prevent rotor speed spikes occurring upon disconnection to result in a false rotation speed condition to be sensed as being above the preset rotation speed threshold; allowing the rotation speed to decrease below the preset rotation speed threshold and following the dead time lockout reconnecting the induction machine to said power grid when the frequency of the remanent voltage again exceeds the preset rotation speed threshold.