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Function and configuration principle  of the motor protection

 
        In all the factories and mine,motors are universally used.Such as belt conveyor, coal feeder, fan and so on,we can see the wide use of  motor.This is all for everyone to see.Because the motor plays an important role in the production, therefore, motor protection is relatively high degree of concern,not only  in order to ensure the stability and safety of the motor operation, but also in order to ensure the production, .
 
three-section current protection    
       Over current instantaneous trip protection is in order to avoid the  setting value when starting current. The time limit can be set for quick break or short time when there is a short-circuit fault, short circuit current is very large, then the fault current reached the setting value, protection device start outlet trip, and then trip
       time delay  over current instantaneous trip protection usually be called locked rotor protection,which is  Automatic connection after the motor is started, the fixed value is adjusted according to the locked rotor current or the starting current.
 
Negative sequence current protection
       Negative sequence current can be generated when the motor is unbalanced.The negative sequence current causes the rotor to overheat,then affect the safe operation of the motor,In order to prevent this kind of phenomenon, then use the negative sequence current protection. 
 
overload protection     
       Over load protection is a reflection of the current magnitude of the stator. When the earth current reaches the setting value and reached the setting time ,the microcomputer protection will alarm or trip,usually alarm
 
Overheat protection
       Overheating protection is generally set to prevent overheating of the motor ,When the overheating protection is tripped and the motor can be started when the temperature is lowered to allow the starting temperature. 
 
Zero sequence over current protection
       Zero sequence over current protection is a reflection of the motor earth grounding, when the zero sequence current reaches a certain value and the setting time limit, the device protection trip  
 
Low voltage protection
       When the three-phase voltage of the motor is less than the value of the setting value.Motor protection trip.
   
       The above is the conventional protection of the relatively small specifications motor,  When the above the 2MW motor or less than 2MW  but the sensitivity coefficient of the current instantaneous trip protection  does not meet the requirements, can be fitted with differential protection ,Longitudinal differential protection can be installed.
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