In recent years, the accident damage to low-voltage motors, about one-third operation of the motor caused by open-phase. People for the motor to run off with the harm caused to the motor has a different point of view, the most important in two points: the first point that the open-phase motor current increases, resulting in damage to motor overheating; the second point that the open-phase leading to the two motor windings have a high-pressure side to back-EMF breakdown. In fact the moment of motor off at both ends of the windings have a several times higher than the rated voltage of the back-EMF to the motor overheating is far greater than the harm caused by the harm caused to the motor, and off does not automatically rule out the possibility of failure, so the open-phase motor protection protection should be used instead of instantaneous movement characteristics of inverse time protection and overtemperature protection.
In this paper, for the three-phase motor protection devices for open-phase analysis and research, design with testing, monitoring and alarm functions of the Open-phase protection device.
