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Several methods of motor phase failure protection

        Motor is the main motive force of modern production. Almost all over the industry. Which is the most widely used three-phase motor. As an electrician, and inevitably come into contact with it. So phase failure caused by three-phase motor failure probability we all know. Let's discuss a variety of broken phase protection.

A voltage protection method

          Voltage protection method is usually to check the three-phase voltage. If one of the phases is disconnected or the voltage is lower than a certain value, then the protection action, make the AC contactor action. Disconnect the main power. Stop the motor. To protect the purpose .

Second: the current balance protection method. 

          The use of current transformers and other detection components. Detection of three-phase current. When the three-phase unbalance and the current value is higher than a certain value. Protection unit action. Disconnect the main power from the AC contactor. To protect The purpose of the motor.

Three: zero sequence current protection method.

          The use of three-phase motor impedance balance. Under normal circumstances, the motor zero sequence current is equal to zero. The motor neutral line connected to the detection of components. Sequence current exceeds a certain value. Protection element action. AC contactor disconnect the main power. To achieve the purpose of motor protection

Four: thermal effect method.

The law sub-heating element external method and built-in method. The following points: 

          1: thermal element external method is widely used, such as thermal overload relay. It often with the AC contactor composed of electromagnetic protection. Quite a wide range of principle is not much to say 

          2: The built-in thermal element is the use of thermistors and other thermal components placed in the winding can accurately measure the internal temperature of the motor when the temperature exceeds a certain value to protect the components action AC The contactor disconnects the mains and protects the motor.

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