What are the motor protection

Update:02-12-2020
Summary:

1 overload protection When the motor is in an overload […]

1 overload protection
When the motor is in an overload fault and runs over its rated current for a long time, it will cause the motor to overheat, reduce insulation and burn out. The protector calculates the heat capacity of the motor according to the heating characteristics of the motor, and simulates the heating characteristics of the motor to protect the motor. Protect the features corresponding to different trip levels.
2 Underload protection
When the load carried by the motor is a pump load, the motor running at no load or under load will cause harm. The protector provides underload protection. When the percentage of the average current of the three phases to the rated current is lower than the set value, the protector should Action within the action (delay) setting time or alarm within the alarm time.
3 stall/block protection
When the motor is starting or running, if the motor shaft is stuck due to excessive load or its own mechanical reasons, and the fault is not resolved in time, the motor will overheat, reduce the insulation and burn the motor. Locked-rotor protection is suitable for the motor Start protection when such a fault occurs. The blocking protection is suitable for protection when such a fault occurs during the operation of the motor. When the current reaches the action set current, the protector should act within the action (delay) set time or alarm Alarm within time.
4 phase failure (unbalanced) protection
Phase failure (unbalanced) operation is very harmful to the motor. When the motor has a phase failure or three-phase current is seriously unbalanced, if the unbalance rate reaches the protection setting value, the protector will protect according to the set requirements and issue Stop or alarm instructions to make the operation of the motor safer.
5 Grounding/leakage protection
The protector has both grounding protection and leakage protection functions. The grounding protection current signal is taken from the vector sum of the internal current transformer, which is used to protect the short-circuit protection of the phase line to the metal shell of the motor. The protector can detect a fault current of 30mA~50mA by adding a leakage transformer, which is mainly used for indirect Grounding protection to ensure personal safety.
6 External fault protection
When the protector detects an external fault and the external fault switch input is inconsistent with the switch input defined by the protector, the protector protects according to the set requirements to ensure the safety of the motor equipment.
7 Starting overtime protection
During the motor starting process, the protector only has the protection functions of open phase (unbalanced), grounding/leakage, etc. The other protection functions do not work. After the start, all the protection functions (according to user settings) are automatically turned on. When the starting time of the motor exceeds the starting time set by the user, and the current is greater than 1.1 times the rated current, the protector will protect according to the set requirements, and issue a stop command within the action (delay) set time to stop the motor.
8-phase sequence protection
For a protector with phase sequence protection function, when the voltage phase sequence on the power supply side is consistent with the set sequence, the protector should not operate. When the protector detects that the electric phase sequence is connected incorrectly, the motor should not start.
9 Undervoltage protection
If the voltage is too low, the motor speed will decrease or even stop running. When the motor's operating voltage drops to the set under-voltage protection range, the protector will perform protection according to the set requirements. It will act within the action (delay) set time or Alarm within the alarm time to avoid confusion caused by important production processes and seriously affect production.
10 Overvoltage protection
Excessive voltage will cause damage to the motor insulation. When the operating voltage of the motor exceeds the set protection voltage, the protector will perform protection according to the set requirements. It will act within the action (delay) set time or give an alarm within the alarm time. Ensure the safety of motor equipment.
11 under power protection
The motor loses its mechanical output capacity due to the damage of the transmission device. When the motor is running under load, the power factor of the motor is low, but the motor current is large, which consumes a large amount of reactive power of the system. When the percentage of load power to rated power is lower than the set action value , The protector will act within the action (delay) setting time or alarm within the alarm time.
12 Overheat protection
The overheating protection uses mathematical methods to establish the heating model of the motor, and solves the thermal protection problem of the low voltage motor in principle.

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