... speed adjustment during operation of asynchronousmotor of AC frequency 50HZ,rated voltage 660V or 1140V,with the good features ... typies of online andshort-time; when online type, the frequency converter can change the speed accordingto its load; with belt ... of over current, short circuit,grounding, phase loss, over voltage, under voltage, over load, over heart, outeralarming and current leakage. ...