Page 73 - MCCB-XT5

ABB | SACE Tmax XT

Protection UC Function
UC protects the motor in reduced or no load conditions: the protection sends a TRIP command if all the
current values detected by the unit drop below threshold luc for longer than time tuc.
To check and simulate the trip times in relation to all the parameters, please consult:
• summary table of the protections with the operating characteristics (page 83)
• the graph with trip curve (page 99)
Parameters
Parameter Description Default
Activates/deactivates the protection and its availability in the
Enable OFF
parameters menu
Activates/deactivates transmission of the open command: if
Trip Enable disabled, the alarm and exceedance of protection time are only OFF
managed as information
Establishes the value that activates the protection.
The value is given as both absolute value (amperes) and relative
Threshold Iuc 0,5 Ir
value (Ir) and can be set within the range: 0.5 Ir to 0.9 Ir in 0.1 Ir
steps
This is the trip time of the protection; the value is given in
Time Iuc 1 s
seconds and can be set within a range: 1 s to 20 s, in 0.5 s steps
Limitations and additional functions
The block functions can also be accessed by means of the service connector (via Ekip Connect) or by
connection to the system bus (page 76).

Protection U Function
U protects the motor in the event of phase loss: the protection sends a TRIP command if the rms value
of at least one phase drops below the 0.1 In threshold and, at the same time, a current exceeds 0.25 for
longer than time tu; the protection is inhibited during Motor start-up.
If an alarm due to U protection occurs during Motor start-up, the trip unit calculates the trip time of the
protection using whichever is the lowest value between: tu and half of Motor start-up
IMPORTANT: in this case, if the alarm occurs on start-up and the calculated TRIP time is
sufficiently long to last even until the Motor start-up window closes, the trip unit still
considers the previously calculated minimum value as TRIP time

To check and simulate the trip times in relation to all the parameters, please consult the summary table of
the protections with the operating characteristics (page 83)
Parameters
Parameter Description Default
Activates/deactivates the protection and its availability in the
Enable OFF
parameters menu
Activates/deactivates transmission of the open command: if
Trip Enable disabled, the alarm and exceedance of protection time are only OFF
managed as information
This is the trip time of the protection; the value is given in
Time tu 1 s
seconds and can be set within a range: 1 s to 10 s, in 0.5 s steps

Limitations and additional functions
The block functions can also be accessed by means of the service connector (via Ekip Connect) or by
connection to the system bus (page 76).

71 | © 2022 ABB | 1SDH002039A1002 - ECN000212994 Protections | 9 - Motor protections