An irrigation system broadly comprising a number of irrigation spans and a control system configured to operate single speed drive motors of the irrigation spans in a start-up mode, full speed mode, and wind-down mode. In the start-up mode, the motor controller gradually increases the drive motor speed from 0 rpms to a full speed by ramping a voltage applied to the drive motor from a starting voltage to a full speed voltage according to a start-up voltage profile over a start-up time interval. In the full speed mode, the motor controller operates the drive motor at a full speed voltage. In the wind-down mode, the motor controller gradually decreases the drive motor speed from full speed to 0 rpms by ramping the voltage applied to the drive motor from the full speed voltage to an ending voltage according to a wind-down voltage profile over a wind-down time interval.
