ABB RELION REX640 Technical Manual page 1094

Protection and control

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Protection functions

Function block

Figure 613: Function block

Functionality

The motor start-up supervision function STTPMSU is designed for protection

against excessive starting time and locked rotor conditions of the motor during

starting. For a good and reliable operation of the motor, the thermal stress during

the motor starting is maintained within the allowed limits.

The starting of the motor is supervised by monitoring the TRMS magnitude of all

the phase currents or by monitoring the status of the circuit breaker connected to

During the start-up period of the motor, STTPMSU calculates the integral of the I²t

value. If the calculated value exceeds the set value, the operate signal is activated.

STTPMSU has the provision to check the locked rotor condition of the motor using

the speed switch, which means checking if the rotor is able to rotate or not. This

feature operates after a predefined operating time.

STTPMSU also protects the motor from an excessive number of start-ups. Upon

exceeding the specified number of start-ups within certain duration, STTPMSU

blocks further starts. The restart of the motor is also inhibited after each start

and continues to be inhibited for a set duration. When the lock of start of motor is

enabled, STTPMSU gives the time remaining until the restart of the motor.

STTPMSU contains a blocking functionality. It is possible to block function outputs,

timer or the function itself.

Analog input configuration

STTPMSU has one analog group input which must be properly configured.

Table 1035: Analog inputs

Improper analog channel configuration causes a validation error if the analog

channels are not completely configured or they do not match with certain settings.

For troubleshooting, check the contents of this chapter and also the preprocessing

See the preprocessing function blocks in this document for the possible

signal sources.

Three-phase currents

1MRS759142 F

Technical Manual