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Motor protector
Date:01/18/2013   Click:851

To protect the motor comprehensive protector for the motor, the motor overload, phase lack, blocking, short circuit,overvoltage, undervoltage, leakage current, three-phase unbalance, overheating, bearing wear, rotor eccentricity,device to alarm or protection. The compressor motor protector is widely used at home and abroad has two kinds:double metal type and thermistor + electronic module type. Their structures are different, the role is also different.

The main purpose is to protect the electric motor protection to prevent burning. In practical application, many causes of motor burned, probably can be divided into the following categories:

(1) motor overload caused by a variety of reasons, the current is too large;

(2) the voltage is too low or too high, phase imbalance or phase (including contactor failure caused by lack of phase)caused by the unbalanced current;

(3) the refrigerant pipeline leakage or problems caused by back pressure is too low, insufficient cooling motor;

(4) the winding insulation layer is damaged or refrigerant water content is too high, short circuit burned etc.. In theory, the overload protector can effectively cope with the first 2 cases, while the thermal protector can cope withthe former 3 cases. The fourth case "short circuit" may be related to quality or the related installation, may also be associated with metal chips or water content of the refrigerant is too high. In actual use, several situations may occur simultaneously, and reinforce each other, not like the laboratory that always use new compressor for testing, and often will simplify the problem. Currently used thermal protector and overload protection device in the maximumlimitation and can not avoid all of the above phenomenon from root to occur, thus the motor protection can only stayin the post "cooling therapy", namely temporarily shut down, let the compressor natural cooling, and then running.Thermal protection and overload protection device without attracting the number of restrictions, motor often burnedin "protection operation again protection - then run" cycle. For emergencies, such as winding caused by copperscraps of insulation damage or short circuit, the motor will be instantaneous burning temperature, thermal protector and overload protection device are not reaction, unable to protect.