Abstract: Systems and methods for averaging a digital phase locked loop output frequency to calculate a preset value for use in the event of a link loss are disclosed. The method may include reading a fractional portion of an output of a digital phase locked loop (DPLL), calculating an integer portion of the output of the DPLL, and accumulating a predetermined number of samples of the fractional portion and the integer portion of the output of the DPLL. The method may include computing an average value of an output frequency of the DPLL over the predetermined number of samples, extracting a fractional portion and an integer portion of the average value of the output frequency of the DPLL, and loading the fractional portion and the integer portion of the average value of the output frequency of the DPLL as preset values in a fractional-N phase locked loop.

Abstract: A method for detecting failure of speed measurement of a multi-phase AC motor includes (1) sensing current drawn by the motor, (2) sensing voltage magnitude supplied to the motor, (3) measuring motor speed, (4) calculating motor speed, (5) determining whether the difference between the measured motor speed and the calculated motor speed is greater than a predetermined threshold, if the difference between the measured motor speed and the calculated motor speed is not greater than a predetermined threshold, repeating (1) through (5), if the difference between the measured motor speed and the calculated motor speed is greater than a predetermined threshold, indicating a fault, if a fault is indicated, performing a predetermined number of restart attempts, if the motor is successfully restarted, repeating (1) through (5), if the motor is not successfully restarted, indicating a restart failure.

Abstract: A method for detecting failure of speed measurement of a multi-phase AC motor includes (1) sensing current drawn by the motor, (2) sensing voltage magnitude supplied to the motor, (3) measuring motor speed, (4) calculating motor speed, (5) determining whether the difference between the measured motor speed and the calculated motor speed is greater than a predetermined threshold, if the difference between the measured motor speed and the calculated motor speed is not greater than a predetermined threshold, repeating (1) through (5), if the difference between the measured motor speed and the calculated motor speed is greater than a predetermined threshold, indicating a fault, if a fault is indicated, performing a predetermined number of restart attempts, if the motor is successfully restarted, repeating (1) through (5), if the motor is not successfully restarted, indicating a restart failure.