Limitations of motor protectors

Limitations of motor protectors The main purpose of motor protection is to protect the motor from burning, and the function of the protector is very limited, which is obviously an impossible task. In practical applications, there are many reasons that can cause the motor to burn down, which can be roughly divided into the following categories: motor overload caused by various reasons, excessive current, too low or too high voltage, unbalanced or missing phase (including contactor failure) The current imbalance caused by the lack of phase); the return air pressure caused by refrigerant leakage or pipeline problems is too low, and the motor is insufficiently cooled; the winding insulation is damaged or the refrigerant moisture content is too high, and the section is burned. In theory, overload protection can effectively cope with the former situation, while thermal protection can cope with the former situation. The short circuit in the first case may be related to quality or installation, or it may be related to metal shavings or refrigerant moisture content is too high. In actual use, several situations may occur simultaneously. And it is a cause and effect of each other. It is impossible to always test with a new compressor like the laboratory, and often simplify the problem. The biggest limitation of the current thermal protector and overload protection is that it is impossible to avoid all the above phenomena from the root, so the protection of the motor can only stay afterwards; cooling therapy; both temporary shutdown and natural compressor Cool and then run. During the thermal protection period and the overload protection period, there is no restriction on the number of suctions and times. The motor is often burned in the cycle of protection and then protection and operation. For sudden events, such as winding insulation damage or short circuit caused by copper scraps, the motor will be burned at high temperature instantly, and the thermal protector and overload protector are too late to respond and cannot be protected. ; Heat; and; Overload; is the appearance of the motor burn rather than the root cause, of course, can not rely on a thermal protector or overload protector to solve the problem, this is why the motor burn can not be completely avoided.