Abstract: A method of, and apparatus for, monitoring the run-up to speed of asynchronous motors which are turned-off within a permissible blocking or cutoff time of the motor when the speed run-up is improper, wherein after turning-on the motor there is determined a first value of an electrical magnitude which is dependent upon the phase angle between the motor current and the motor voltage after expiration of a first time-delay following turning-on of the motor, and there is then determined a second value of said electrical magnitude after expiration of a second time-delay following the turning-on of the motor. Both the first and second values are compared with one another, and the motor is turned-off when, following such comparison, there is present a magnitude indicative of improper run-up to speed of the motor.