ABB SACE Tmax XT2 User Manual page 68

UC Protection Function
UC protects the motor under reduced or no-load conditions: if all the currents read by units fall
below the Iuc threshold for a time greater than tuc, the protection sends the TRIP command.
To verify and simulate the trip times based on all the parameters, see:


Parameters
Parameter
Enable
Trip Enable
Threshold
Iuc
Time tuc
Constraints, limitations, and additional functions
From the service connector (with Ekip Connect) or with system bus connection it is also possible
to access the block functions, see page 70.
Function
U Protection
U protects the motor in case of loss of a phase: if the rms value of at least one phase falls below
the threshold of 0.1 In and at the same time at least one current is greater than 0.25 for a time
greater than tu, the protection sends the TRIP command. The protection is inhibited during Motor
start-up.
If the U protection alarm occurs during Motor start-up, the trip unit calculates the trip time using
the lower value between tu and half of Motor start-up.
To verify and simulate the trip times based on all the parameters, see:

Parameters
Parameter
Enable
Trip Enable
Time tuc
Constraints, limitations, and additional functions
From the service connector (with Ekip Connect) or with system bus connection it is also possible
to access the block functions, see page 70.
1SDH002031A1002 ECN000092998
Protection summary table with the operating characteristics (page 80)
Chart with tripping curve (page 95)
Description
Enables/disables protection and availability on menu of the
parameters
Activates/deactivates the open command: if disabled, the alarm
and the lapsing of the protection time are managed only as
information
Defines the value that activates the protection.
The value is expressed both as an absolute value (A) and as a
relative value (Ir), settable in a range: 0.5 Ir .. 0.9 Ir, con step 0.1 Ir
This is the trip time of the protection; the value is expressed in
seconds, which are settable in a range: 1 s .. 20 s, con step 0.5 s
IMPORTANT: in this case, if the alarm occurs at start-up and the calculated TRIP
time is such that it persists even at the close of the Motor start-up window, the
trip unit still considers the minimum value previously calculated as TRIP time
Protection summary table with the operating characteristics (page 80)
Description
Enables/disables protection and availability on menu of the
parameters
Activates/deactivates the open command: if disabled, the alarm
and the lapsing of the protection time are managed only as
information
This is the trip time of the protection; the value is expressed in
seconds, which are settable in a range: 1 s .. 10 s, con step 0.5 s
Rev. B
Default
OFF
OFF
0.5 Ir
1 s
Default
OFF
OFF
1 s
SACE Tmax XT2 – XT4 | 68