Protection technology generally used for three-phase asynchronous motor stator windings burned, overheat protection, over-current protection and phase failure protection.

    1, overheat protection part of the view that no matter what the cause of failure will eventually lead to the stator windings of the motor overheating and burning. Therefore, as long as to prevent overheating of the motor windings, also the protection of the motor. But in fact, the motor itself, there is the difference of the thermal insulation level. Class A 105 ° C, and E grade 120 ° C, Grade B 130 ° C, Grade F 155 ° C, a level H 180 ° C, in the same ambient temperature, the working conditions, the temperature rise of the case, and some electrical opportunity to damage the maximum allowable temperature rise, but some will not be damaged. Bearing damage caused by overheating of the motor causes the stator and rotor rubs, poor ventilation, such as the case of electrical periodic inspection and inspection checks must be found to solve, in the case of the scope of protection technology. In addition, the motor temperature, cooling is a slow process of change, we believe that only work for large and medium-sized, important positions installation of motor temperature rise monitoring and overheating protection device is necessary. And should be based on different heat levels set in the interior of the motor ultra-temperature alarm and then tripping device. As for the small motor overheating protection device is not necessarily cost-effective.

    2, overcurrent protection for almost constant motor load, over-current protection is not necessary. However, some motor load changes frequently, often overload, stall and even burning motor windings. Overcurrent protection devices must be installed and running motor. Although the three-phase asynchronous motor strong overload capacity, but the implementation of the inverse-time characteristics of motor overload protection is necessary, and it is recognized by the public.

    3, phase failure protection motor damage, mostly caused by phase Running awareness of the harm caused to the motor run off, so the implementation of the motor phase failure protection are two different views: that the loss of phase the overheating damage caused to the motor point of view to the implementation of the motor overheating protection or overcurrent inverse-time characteristics of protection, the resulting thermal relay solutions, the thermistor programs, off delay overcurrent protection program and other programs; think off phase to the motor windings caused by the high voltage back EMF breakdown point of view, off the action instantaneous protection program, so the advent of electronic protection.