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What are the ways of Motor protection ?

1. Overload protection
When the motor runs over the rated current for a long time under the overloaded fault, it will cause the motor to overheat, reduce the insulation and burn down. The protector calculates the thermal capacity of the motor according to the heating characteristics of the motor. The characteristics of different tripping levels corresponding to the protection of the motor by simulating the heating characteristics of the motor and the overload protection.
2 . Underload protection 
When the load of the motor is the pump type load , the motor no - load or under - load transfer is harmful , the protector provides under - load protection , and when the percentage of the average current of the three - phase and the rated current is lower than the set value , the protector shall operate within the action ( delay ) setting time or alarm within the alarm time .
3, blocking / blocking protection
When the motor is starting or running, if the electric timing shaft is jammed because of excessive load or its own mechanical reasons, and the fault is not solved in time, it will cause the motor to overheat, reduce the insulation and burn down the motor. The clogging protection is suitable for the protection of the motor starting such faults, and the blocking protection is suitable for the protection of the motor in the process of operation, when the current reaches the action setting current. The protector should act within the action (delay) setting time or alarm time.
4, fault (unbalance) protection
Phase (unbalanced) fault operation of the motor is of great harm, when the motor open phase or three-phase current imbalance, such as unbalanced rate of protection setting value, protection in accordance with the protection requirements set, stop or alarm instructions, to make the motor running safely.
5, grounding / leakage protection
The current signal of the grounding protection is taken from the vector sum of the internal current transformer, which is used to protect the short circuit protection of the metal shell of the motor by the phase line. The protector can detect the fault current of 30mAn 50mA by increasing the leakage transformer, which is mainly used for the protection of indirect grounding to ensure personal safety.
6, external fault protection
When the protector detects an external fault and the input of the external fault switch is inconsistent with the input state of the switch defined by the protector, the protector protects according to the set requirements to ensure the safety of the motor equipment.
7, starting timeout protection
In the motor starting process, only has a phase interruption protector (unbalance), grounding / leakage protection function, the protection function does not work, in the end of starting, all protective functions (set by the user) are automatically input, when the motor starting time set the starting time is greater than the current user over. 1.1 times of rated current, protection in accordance with the protection requirements set, in action (delay) issued a stop command set time, stop the motor running.
8, phase sequence protection
A protector with phase sequence protection function, when the voltage phase sequence of its power side is in accordance with the setting order, the protector should not act. When the protector detects the phase sequence of the electric D, the motor must not start.
9, under-voltage protection
If the voltage is too low, the speed of the motor will decrease or even stop running. When the operating voltage of the motor drops to the undervoltage protection range, the protector will protect the motor according to the set requirements. During the action (delay) set time or alarm time, to avoid the important production process caused confusion, serious impact on production.
10 . Overvoltage protection 
The voltage is too high to cause damage to the insulation degree of the motor . When the operating voltage of the motor exceeds the set protection voltage , the protector shall be protected in accordance with the set requirements . During the operation ( time delay ) , the protector shall be actuated or the alarm is alarm within the alarm time to ensure the safety of the motor equipment .
11, under-power protection
The power factor of the motor is low when the underload is running, but the current of the motor is very large, and the reactive power of the system is consumed greatly because of the damage of the transmission device and the loss of the mechanical output ability. When the percentage of load power to rated power is lower than the set action value, the protector acts during the action (delay) setting time or during the alarm time.
12, overheat protection
The heat model of motor is established by mathematical method, and the thermal protection problem of low voltage motor is solved in principle.


 
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