DOCA0189EN–05

Phase Loss Protection

Overview

The phase loss protection is used to protect three-phase asynchronous motors against phase loss conforming to the IEC 60947-4-1 and UL 60947–4–1 standards.

The phase loss protection can be used to protect three-phase IE1, IE2, IE3, and IE4 asynchronous motors.

Phase loss causes the overheating of the motor. It occurs in case of blown fuses or loose power connection.

Operation

The overload relay calculates the rms current value in each phase continuously. When the rms current value in one of the three phases is lower than 0.1 Ir and the rms current value in another phase is greater than 0.8 Ir, the overload relay triggers a tripping in 4 +/- 1 s.

NOTE: The phase loss protection cannot be disabled.

Manual Reset

The phase loss protection can be reset manually only. For more information, refer to Trip Reset.

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